Perinatal and neonatal death clustering in an Italian sharecropping … · 2014. 9. 30. ·...
Transcript of Perinatal and neonatal death clustering in an Italian sharecropping … · 2014. 9. 30. ·...
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Perinatal and neonatal death clustering in an Italian sharecropping community in the first
half of the nineteenth century
Francesco Scalone,
Patrizia Agati, Aurora Angeli, Annalisa Donno
Department of Statistical Sciences – University of Bologna
(DRAFT – PLEASE DO NOT QUOTE)
Introduction
Our object was to study the determinants of perinatal and neonatal mortality in the Italian village of
Granarolo from 1900 to 1939, focusing on the phenomenon of high risk mothers and clusters of
stillbirths and neonatal deaths at family level. We considered late fetal life and early neonatal
mortality, assuming stillbirths and deaths in the first weeks of life as perinatal death. We also took
into account late neonatal mortality between 7 and 30 days after childbirths. Causal structures of
neonatal mortality and stillbirths already emerged as broadly similar (Reid 2001), depending on
factors such as maternal age, parity, spacing of births and changes in birth weight distribution
(Waaler 1984). Endogenous factors, such as genetic make-up, congenital malformations,
prematurity and negative circumstances at childbirth determinate perinatal mortality risks.
Nevertheless, perinatal and neonatal variability pattern appears too sensitive to environmental
factors to be entirely related to purely endogenous causes (World Health Organization 2006)
A definition of infant death clustering can be based on the concentration of deaths within some
families or on the number of women who have lost more than one child, the so-called high-risk
mothers (Edvinsson and Janssens 2012). Among historical demographers, the notion that infant
deaths were unevenly distributed among families was first highlighted by Lynch and Greenhouse
(1994). After this seminal paper, other studies focused on this phenomenon demonstrating that
infant mortality was mainly clustered in a restricted number of high-risk families (Edvinsson and
Janssens 2012). Historical research on infant death clustering phenomenon can also be relevant to
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understand the determinants of high-risk mothers in contemporary populations, better addressing
health interventions for reducing early mortality (Arulampalam and Bhalotra 2006; Zaba and David
1996).
Several previous studies already took into account genetic, bio-demographic and socioeconomic
determinants of infant death clustering. Despite a considerable interest, socio-economic
mechanisms of infant death clustering still need to be further investigated (Edvinsson and Janssens
2012) and less attention has been devoted to the effects of household structures and family
arrangements in determining infant mortality clustering.
From this perspective, sharecroppers’ families living in northern and central Italy in the past offer
some relevant features that make them interesting from the historical and theoretical point of view.
For centuries sharecroppers were pressed by their landowners to have large families in order to
increase the agricultural production (Barbagli 1984). Individuals living in these large, multiple and
multi-generation households could rely on the assistance of co-resident relatives, involving all
aspects of life (Laslett 1988). According to our view, co-residential kinship could also provide
security and support during pregnancy, delivery and neonatal life, mitigating the effects of parental
incompetence (Das Gupta 1997), genetic frailty and bio-demographics disadvantages. In multiple
and extended families, grandmothers, aunts or other older women could assist at childbirth and give
help in case of complications. Therefore, a less frequency of high risk mothers among sharecroppers
is expected.
In the same agricultural system, another group of rural proletarians coexisted. Daily wagers were
the more vulnerable segment of the rural population, since they could not rely on any agrarian
contract and were hired on daily and weekly bases. Given their precarious conditions, they
generally lived in smaller nuclear families. Consequently, we expected to find a higher
concentration of perinatal and neonatal deaths among their families, since in nuclear households
mothers were more isolated and could not rely on the helps of other women and relatives.
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So our aim was to assess whether or not family context could mitigate the effects of adverse
genetics, endogenous factors and precarious female conditions.
Since birth weights and perinatal mortality were also determined by women’s living standards
(Ward 1993) and female physical labor was associated with a higher number of stillbirths (Reid
2001), high risk mothers are expected to have been more frequently involved in rural agricultural
works. Granarolo represents a relevant study case since women in rural families could frequently
take responsibilities in both house and field works (Ropa and Venturoli 2010). However, because
their privileged position, we hypothesized that sharecropper’s wives could be more protected than
daily wagers’ wives and got assigned less demanding physical tasks during pregnancy.
Traditional determinants often fail to explain why some families were more exposed to infant and
child mortality than others. Because of this unobserved heterogeneity, it is no longer useful for
infant mortality analysis to examine children only as unrelated individuals. Considering infant
deaths as correlated within the same family implies the adoption of multilevel models. So we used a
statistical multivariate method to properly measure amount, shape, and dispersion of death
clustering among mothers of sharecroppers, daily rural wagers and other socioeconomic groups,
controlling for several bio-demographic factors, seasonal effects and different historical periods.
In the next section of this paper, we provide our theoretical framework briefly reviewing the main
literature on both perinatal and neonatal mortality, infant death clustering and the nuclear hardship
hypothesis. Then we present the area under study, the data and the method used. We also list the
covariates in the multivariate analysis, discussing their expected effects. We then present and
discuss the empirical results.
Theoretical framework
Perinatal and neonatal determinants
As stated by World Health Organization (2006) causes and determinants of neonatal deaths and
stillbirths differ from those related to post neonatal and child deaths. Early neonatal deaths occur
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during the perinatal period, and have obstetric origins, similar to those leading to stillbirths, whereas
infections are the main cause of neonatal death in many countries after the first week of life.
Neonatal deaths and stillbirths derive from poor maternal health, inadequate care and management
of complications during pregnancy and delivery, poor hygiene and lack of newborn care.
Complications during birth, such as obstructed labor and fetal malpresentation, are common causes
of perinatal death in the absence of obstetric care. Harmful practices such as inadequate cord care,
letting the baby stay wet and cold, discarding colostrum and feeding other food can further affect
neonatal survivorship.
Several maternal factors are related to perinatal and neonatal mortality such as women’s status in
society and nutritional state at the time of conception. In early or late childbearing, mother’s age
represents another risk factor. According to the maternal depletion hypothesis (Winkvist et al.
1992), short inter-birth intervals generally impoverish maternal physiological state, increasing
perinatal and neonatal mortality risks (Da Vanzo et al. 2008).
Considering neonatal conditions and characters, babies die immediately after birth since they are
severely malformed, are born very prematurely, suffer from obstetric complications before or
during birth, have difficulty adapting to extrauterine life or because of harmful practices after birth
that lead to infections (World Health Organization 2006).
Causes and mechanisms of infant death clustering
Variations in the distribution of mortality risks for children between families or mothers can be
explained by differentials in bio-demographic, socioeconomic and cultural features (Edvinsson and
Jansen 2012; Zaba and David 1996). Underlining the effects of physiological and demographic
factors, several authors have suggested that maternal depletion could play a main role in increasing
child mortality risks among high-parity mothers (Zaba and David 1996, Miller et al. 1992). It also
appears that the death clustering is related to the frequency with which families experienced
stillbirths (Edvinsson et al. 2005; Reid 2002). Beyond bio-demographic determinants, genetics may
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also have a role in determining death clustering patterns. Genetic factors are almost impossible to be
measured in historical research, but their relevance emerges by the difficulty in explaining mortality
clustering adopting biological and socioeconomic predictors only (Edvinsson and Jansen 2012).
Even if primary causes of perinatal and neonatal death have an endogenous origin, individual socio-
economic characteristics together with environmental, hygienic and sanitary conditions could exert
an indirect effect, improving or worsening women’s health, maternal nutrition and obstetrical
quality. A negative combination of these factors could contribute in unevenly distributing perinatal
and neonatal deaths at mother level, creating mortality clusters and high risk mothers.
Socioeconomic parents’ characters such as occupation, social class, income, and education
represent other sources of infant death clustering, since they worsen health inequalities (Graham
and Kelly 2004). Wider environmental factors at community, neighborhood and family
environments have to be taken into account as well. In previous studies, Guo (1993) showed that
household income and mother’s educational attainment are important determinants of infant death
clustering at familial level in Guatemala, while Das Gupta (1997) demonstrated that in India
socioeconomic status has a fundamental role, even greater than household income. However, in
some historical studies, after controlling for several bio-demographic factors, household’s socio-
economic status and income do not significantly explain familial component in infant mortality
differences (Lynch and Greenhouse 1994; Janssens et al. 2010).
Breastfeeding behavior, quality of maternal care or parental attitudes could affect children’s health
and might be responsible for the clustered outcomes. The much-debated “maternal incompetence”
is seen as a basic inability to manage domestic affairs, regardless education, income, and occupation
(Das Gupta 1997).
The “nuclear-hardship” hypothesis
In pre-industrial societies, individuals living in nuclear families were less protected than those
living in extended and multiple households. According to the “nuclear-hardship” hypothesis, before
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the creation of a modern system of welfare and assistance, nuclear families were much more fragile
than today, since their members were more exposed to the consequences of negative events such as
the death of a spouse, unemployment, sickness or senility (Laslett 1988). Co-resident domestic
groups instead provided assistance and security for all members, ensuring the survivorships of
elderly people, widows and orphans. As Peter Laslett (1988) noted, this could be the case of the
Italian sharecroppers that used to live in large-scale, multiple and multi-generation households. In
addition, other studies already demonstrated that household structure could affect the women living
conditions in historical rural societies. Within non-nuclear rural households, women used to activate
both solidarity networks towards children and forms of horizontal solidarity among women
themselves (Palazzi 1990).
In our theoretical framework, material security and psychological support from co-residential
kinship protected newborns and new mothers during pregnancy, at childbirth and in the first periods
of life. They could rely on domestic food resources and consequently be in a better nutritional
status. Moreover, solidarity of relatives could protect pregnant women and new mothers from heavy
agricultural works, replacing them in the fields or not assigning them heavy tasks. Probably female
daily wagers were not in such conditions and could not have similar securities and protections. In
addition, material support from other family members could help mothers and newborns during
delivery. In a multi-generation sharecroppers’ household, older and more competent women could
successfully manage difficult childbirths and avoid harmful practices in childrearing. So a woman
with adverse biological and genetics background living in a sharecropper’s household had more
probability to give birth to a live-born and protect his surviving than a mother in a nuclear family.
Area
Granarolo is a rural village situated about ten kilometers far from Bologna, in Emilia-Romagna, a
northern Italian region. This region comprises the southern part of the Padan Plain and the first hills
of the Apennines Chain. Bologna is geographically located in the central area of Emilia-Romagna
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and for centuries has been crossed by people travelling for economic, working, and cultural reasons.
The root of Granarolo word is “granary”, suggesting its ancient role as granary of Bologna. Because
of its proximity to the urban area, Granarolo always exchanged goods, agricultural products and
practical knowledge with Bologna.
During the period under analysis, the economy of Granarolo was prevalently rural. At the 1911
census, the majority of household’s heads was employed in agriculture with 47 per cent of farmers
and sharecroppers and 24 per cent of rural daily wagers (Istituto Centrale di Statistica del Regno
d’Italia, 1911). Twenty years later at the 1931 census, agriculture was still the most relevant sector,
counting 47 per cent of sharecroppers and farmers and 21 per cent of rural daily workers (Istituto
Centrale di Statistica del Regno d’Italia, 1937).
Before industrialization, in northern and central Italy, and especially in Emilia-Romagna, the
prevalent agrarian system was based on sharecropping contracts (Bellettini, 1971). Farmers, small
landowners and sharecroppers had quite stable economic conditions, relying on their own properties
or on their sharecropping contracts. Conversely, rural daily wagers could just count on seasonally or
temporary income, without any contractual protection.
For centuries, the economy played a strong role in household settlements, since the sharecropping
system required a constant supply of male workers and therefore a specific family organization.
Under pressure from their landowners and to avoid an imbalance between work force and farm size,
the safest way to guarantee the continuity of the domestic workforce was to live in large-scale
multiple families (Angeli 1983; Barbagli 1984; Poni 1978; Doveri 2000). In the sharecropping
system, household represented the basic unit of production, with a high level of self-sufficiency; all
family members had to work on farm, including women and children generally dealing with less
demanding tasks.
Since children represented the future workforce to be invested in the agricultural activities,
sharecroppers had generally higher fertility levels with respect to other rural workers (Breschi et al.
2014; Kertzer and Hogan 1989; Rettaroli and Scalone 2012). Moreover, higher infant and neonatal
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survival levels were related to the more substantial family resources and better infant care from co-
resident women (Breschi et al. 2000).
In fact, family members could share material sources, emotional support and practical information
that could make the difference in critical life moments.
Conversely, daily wagers and rural labourers used to live in smaller nuclear families, since they had
no land to cultivate and scarce material sources. With low wages – even lower for women – and an
uncertain number of workdays during the year, wage labourers lived precariously, badly nourished
and clad, in poor housing conditions. High frequency of illness often reduced them to penury (Jacini
1884).
From the beginning of the twentieth century, a rapid development of a large-scale, capitalist
agriculture took place on the north-east plains of Bologna. Sharecroppers’ households contributed
to the creation of an economic system in which farming was combined with work in the industrial
sector (Villani 1989; Cazzola 1985). The new agrarian capitalism implied a progressive
proletarization of the rural workers, still making the daily wagers’ conditions more unstable and
precarious during the period under analysis (Cazzola 1996; Calanca 2004). Despite the substantial
economic, political, and social changes characterizing this period the proportion of sharecroppers
living in the area of Bologna did not significantly decrease and remained quite stable (Kertzer and
Hogan, 1989).
In the first decades of the twentieth century, the Bologna’s area progressively experienced the
impact of the urbanization process, developing manufacturing activities, transport infrastructures
and the sanitary system and attracting growing migration fluxes (Scalone and Del Panta, 2008). As
a consequence, the population of Granarolo increased from about 4.6 thousand in 1901 up to 5.1
thousand in 1921, then remaining stable until the middle of the twentieth century at around 5
thousand inhabitants.
During the first half of the twentieth century, Emilia-Romagna experienced progressive
improvements in survivor conditions: life expectancy at birth for both genders grew from 43 years
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in 1901 to 68 years in 1951, while infant mortality steady declined because of the reduction in
neonatal mortality (Pozzi 2000). Infant mortality decreased in the region from about 170 per
thousand in 1901-1910 to about 81 per thousand in the 1930s. In the same period the neonatal
mortality rate declined from about 78 per thousand to about 42 per thousand (ISTAT 1975). Both
infant and neonatal mortality were higher in Emilia Romagna with respect to the Italian levels until
around 1920 (Bellettini, 1981); in the following decades the regional rates faster fell, reaching the
Italian levels.
In Granarolo, infant mortality rate declined from 168 per thousand in 1881-1900 to 96 per thousand
in 1921-1940, a lower level than either regional and national averages (Scalone et al. 2013).
In the province of Bologna perinatal mortality rates fluctuated between 50 per thousand and 150 per
thousand during the last decades of the nineteenth century and the beginning of the twentieth
century, to reach a level between 40 per thousand and 80 per thousand in the 1920s, and 20 per
thousand during most of the 1930s (Ward 2004). Perinatal mortality rates - as well as the infant
mortality levels - were lower in the province of Bologna with respect to those registered in the
whole Emilia-Romagna region. Differences were due to better geographic-environmental conditions
(Angeli, Del Panta and Samoggia 1995) and to improvements in obstetrical assistance and infant
care, already advanced in the early nineteenth century (Scalone et al. 2013). The first Italian chair in
obstetrics was instituted in 1804 at the University of Bologna, and obstetric and gynecological
clinics were established in 1860 in two hospitals (Ospedale Sant’Orsola and Ospizio Esposti), thus
favouring the reduction of stillbirths and perinatal risk, also among poor rural women (Ward 2004).
Historical sources referred to nineteenth century record both the attention of hospital pediatricians
towards rural children’s health and the presence of midwives in the area under analysis (Rosa,
Vegetti 2006; Lo Conte 2013). The rising interest towards maternal and child health could also have
protected rural women delivering at home and contributed to lower children early mortality.
Stillbirths rate in 1931 was 29.9 per thousand in Emilia Romagna (versus 34.3 per thousand in
Italy), while the perinatal mortality rate was 53.4 per thousand, almost equal to the Italian rate
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(ISTAT 1975). In Italy, late-fetal mortality rates only reached credible levels during the early
decades of the twentieth century, after a long process of registration improvements (Del Panta
1997).
Data
Data used for the analysis came from civil births, deaths and marriages registers of the Granarolo
Municipality, available from 1866. The traditional method of family reconstitution (Fleury and
Henry 1956) was applied by preliminary linking births registers to deaths and marriages registers.
For each newborn, death, birth and maternal marriage dates were used to calculate the individuals’
life duration, parity and mother’s age at childbirth. Mortality estimates based on this kind of family
reconstitution are generally biased by unobserved migrations, because of the lack of death dates
when individuals moved and died in another place. However, this bias has generally a limited
impact on perinatal or neonatal mortality measures, since it was not so frequent that a new mother
and her newborn could migrate to another place within a week or a month of delivery.
Nevertheless, for mothers who were born and married outside Granarolo, birth and marriage dates
could remain unknown. Therefore it has been necessary to further search for those mothers in the
1911 and 1931 micro census data to extract their birth date. Since 1931 census data also reported
marriage duration for each married women, other mothers’ dates of marriage were found. However
in a certain quote of childbirths, it was not possible to know mother’s birth and marriage date. In
these cases, maternal age and parity remained unknown.
Stillbirths and immediate neonatal death after childbirth were noted in the birth register, instead of
being reported in the death register. In all these cases, the Italian municipality officers wrote a note
reporting that the newborn was not alive at the moment of the registration without specifying
whether or not he or she was stillbirth or live-born (Breschi et al. 2012). In Granarolo, stillbirths
were frequently reported as “Nato Morto” or “N. M.” in a handwritten note on the border of the
document. As this information was not systematically reported, in some periods the calculated
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stillbirth rates were too low or suspiciously equal to zero. Considering the date (and hours) of
childbirth reported in the birth registration, it was possible to deduct that these cases could only
concern stillbirths and early neonatal deaths occurred within two days of delivery. Because of that,
we decided to refer this analysis only to perinatal deaths, including stillbirths and early neonatal
deaths, and late neonatal deaths identified with a fair degree of certainty.
The births register also contained name and surname of the newborn, birth’s date and place,
maternity, paternity, parents’ occupations, legitimacy and multiple births. The signature at the end
of the birth registration, made also possible to deduct both the presence and literacy of the father.
We totally considered 4918 childbirths from 1900 to 1939, counting 4827 live-born, 91 stillbirths,
150 deaths within 7 days of delivery and 92 between 7 and 30 days. The perinatal mortality rate
(stillbirths plus death in the first week of life) was equal to 49 per thousand and late neonatal
mortality rates equal to 19.7 per thousand.
Method
Data consisted of n newborns grouped into k families, where a family is defined as a mother and her
children. Each newborn had a vector of covariates, x, whose (fixed) effects could be estimated and
were represented in a vector of coefficients β. The k mutually independent cluster variables, u1, u2,
… uk were not to be estimated, since they were not of interest per se; rather, it was the heterogeneity
between clusters that needed to be estimated. To this aim, a normal distribution was assumed for the
u’s, and parameters characterizing this distribution were used to assess the magnitude of the
unexplained interfamily variation.
Therefore, a generalized linear mixed model (GLMM) – that is, an ordinary logistic regression with
a cluster random effect – was used to estimate both the unexplained interfamily variation
(Holmberg and Broström, 2012) and the effects of the selected predictor variables on the
perinatal/neonatal mortality. In symbols:
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( ) ( )
( ) i = 1, 2, …, k ; j = 1, 2, …, ni
where Yij is the (dichotomous) response variable associated to the infant j in family i, and the ui’s
are the k random cluster effects, assumed to be independent and identically distributed as Gaussian
with a mean of zero and variance σ2: in symbols, ui N (0, σ
2) i.
Such a kind of hierarchical (or multilevel) model has a number of advantages over the conventional
(fixed-effects) regression technique:
a) it allows to take into account the clustered nature of data (newborns grouped by mothers):
by treating the groups as a random sample from a population of groups, inferences can be
made beyond the groups in the sample;
b) it recognizes the multilevel structure of data and prevent the standard errors of regression
coefficients to be wrongly estimated, leading to an overstatement or understatement of
statistical significance for the coefficients of the covariates.
Traditional measures of variation between clusters in a random-effects logistic regression are:
- the intraclass correlation coefficient computed as proportion of the total variation attributable to
variation between clusters. It does not convey information about heterogeneity between clusters and
it is not a very useful measure when determining whether or not clustering is a relevant factor.
Besides, is not directly comparable with fixed effects measures, usually expressed in terms of
odds ratios;
- the variance (or the standard deviation) of u itself, : but it is quite difficult to interpret, since it is
on the log odds ratio scale.
Due to the interpretational drawbacks just described, results in this paper have been showed also in
terms of median odds ratios (MOR), a new measure of heterogeneity between clusters suggested by
Larsen and Merlo (2005) and directly comparable with fixed-effects odds ratios. The MOR is based
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on the comparison between two individuals with the same covariate values from two different,
randomly chosen, clusters. The MOR is the median of the odds ratios between the individual of
higher propensity and the individual with a lower propensity across repeated samples. The MOR
was computed as a function of the cluster variance:
MOR = [√ ]
where is the 75th
percentile of the standard normal distribution.
This measure is always greater than or equal to 1: if it is 1, then there is no variation between
clusters; if it is large, then the heterogeneity between clusters is considerable.
For all of models in the analyses Stata 12 was used (Stata Statistical Software: Release12. College
Station, TX: Stata Corp LP).
Variables
Outcome variables
We have examined three different early mortality risk outcomes: perinatal mortality risk (still births
and deaths in the first week of life); late neonatal mortality risk (deaths 7-30 days); risk in the first
month of life (still births and deaths in the first 30 days of life).
As in many historical studies, considering perinatal mortality sidesteps the problems of
distinguishing stillbirth from live births (Ward 2004).
Explicative variables
Sex of the newborn
Several studies on neonatal and infant mortality (Drevenstedt et al. 2008; Pinnelli, Mancini 1997)
highlight that child’s sex contributes in determining the risk of early death: due to biological factors,
male infants have a higher risk of mortality than female.
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Multiple births
Among historical populations, newborns of a multiple delivery showed higher levels of perinatal
and neonatal mortality (Reid 2001; Wrigley et al. 1997), mainly associated with lower birth-weight
of twins or triplets. Since twins tend to be delivered earlier, they have a smaller size and are
consequently more vulnerable than other children, as birth-weight is one of the most important
factors affecting neonatal survival (Conde-Agudelo, et al 2012; Matteson et al. 1998; Ward 1993;
Reid A., 2001).
Age of the mother
The age of the mother plays a relevant role in perinatal and neonatal mortality and has been widely
discussed in the literature. In young mothers, mother-fetus competition for nutrients and/or maternal
incomplete physical growth might contribute to adverse neonatal outcomes (Kramer and Lancaster,
2010). An advanced mother’s age can be related with other risk factors such as maternal
morbidities, congenital abnormalities and neonatal inability to withstand bouts of infectious disease
(Pozzi, 2002; Carolan and Frankowska, 2011). To take into account higher risks of perinatal and
neonatal mortality at younger and older maternal ages, a five-category variable was included. As
shown in table 1, there was a proportion of mothers whose age at delivery was unknown, because
they were born far from Granarolo.
Parity
Birth order may affect the risk of neonatal mortality. Several studies show a J-shaped effect of
parity, with the probability of infant mortality declining after the first child and increasing again for
four and higher orders (Knodel 1988). During perinatal and neonatal life, the greater vulnerability
of first-born has already been demonstrated (Reid 2001). At higher parities, a large number of living
children may affect parental investment in child rearing and the ability of the mother to care for her
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newborns may decrease as her energy level declines (Matteson, Burr and Marshall 1998). To
account for the parity effect and to control for the effect of current family size (Lynch and
Greenhouse 1994), a four level categorical variable was introduced: first newborns, second and
third birth order, four and higher birth order. A last category was introduced for unknown parity
childbirths, when mothers arrived in Granarolo after marriage and it was impossible to fully
reconstruct their reproductive histories. This covariate was constructed by considering any previous
childbirth, therefore including previous stillbirths in the parity count.
Birth interval
The length of interpregnancy intervals has been associated with the risk of adverse perinatal
outcomes (Conde-Agudelo et al. 2006).
According to the maternal depletion hypothesis, a short birth interval may negatively affect
maternal and neonatal nutritional status (Erickson 1978; King 2003) and may give mothers
insufficient time to recover from the nutritional burden of pregnancy, compromising their ability to
support fetal growth (Hobcraft et al 1985; Federick and Adekstein 1973; Winkvist et al. 1992).
Moreover, when births are closely spaced the breastfeeding of the newborn is affected by the
overlap of breastfeeding with pregnancy. We specified a three-category variable to take into
account birth intervals lower than 18 months, between18 to 30 months and greater than 30 months
(see table 1).
Maternal History
As suggested by Reid (2001), to investigate the role of the mother’s features in determining the risk
of perinatal and neonatal mortality, a variable representing the maternal reproductive history has
been taken into account.
Basing on the nominative family reconstitution, for each newborn in a family we preliminary
computed the number of mother’s deliveries, the number of previous infant deaths within one year
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of childbirth as well as the number of previous stillbirth. Then the measure was obtained dividing
the sum of previous infant deaths and stillbirths by the number of children previously born.
This variable could reflect the ability of the mother as the main care-giver, through her health and
child-care competences. It also could represent a proxy of the hygienic level of the household and
of maternal ability in managing household facilities (Reid 2001).
Season
Infant and neonatal mortality in Italy, at least until the beginning of the nineteenth century was
strongly affected by climatic conditions. Several studies on infant mortality in northern and central
Italy (Breschi et al. 2000; Breschi and Livi Bacci 1994) showed a U-profile of the neonatal
mortality by month (or season of birth) and an evident relationship with lowest winter temperatures
(Dalla Zuanna and Rosina 2011; Derosas 2009; Ferrari and Livi Bacci 1985).Therefore we have
also controlled for a seasonal effect, expecting that winter born children had the greatest risk of
neonatal mortality, whereas those born in summer experienced the lowest levels.
Socio-economic Status
We have also taken into account the socio-economic status considering the father’s occupation at
birth. A close connection between socio-economic status and neonatal mortality was expected
(Breschi et al. 2000; Reid 2002; Derosas 2003). The classification scheme distinguished among:
professionals, clericals and sales workers; skilled and low skilled workers; farmers and
sharecroppers; rural daily wagers (including unskilled persons whose job opportunities and earnings
were uncertain and might change daily). A category for unknown socio-economic status was
introduced for illegitimate newborns without father’s indication in the birth registration.
Mother rural status
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Civil birth registers also reported the mother’s occupation, helping in understanding women’s
conditions during pregnancy. In a rural context, because of the need to contribute to the family
sustenance, it is plausible that working women in agriculture did not stop to work in the fields
throughout pregnancy, thus making the likelihood of adverse perinatal outcomes increase (Reid
2001). To take into account this aspect, we introduced a covariate on mothers’ working status. This
dummy variable distinguished newborns from mothers involved in rural work (daily wagers or
farmers) from those born from mothers not involved in rural works (housekeepers, other women not
involved in rural work). Sharecroppers’ wives registered as housekeepers have been included
among not rural working women.
Father's presence and ability to sign
A categorical variable refers to the father presence at birth’s registration and his ability to sign the
document, further specifying the social status of the father. This information also allowed
identifying newborns whose father was far from home at the delivery moment and probably in the
following days (because of work or war reasons). These newborns were generally declared by the
obstetrician.
A higher mortality risk was expected for newborns whose fathers were illiterate or not present.
Period
Social and economic changes of the first half of the twentieth century improved the living
conditions of the rural population. Relevant progresses in obstetrical techniques and sanitary
organization contributed to reduce infant mortality levels in this rural area (Scalone et al. 2013).
Considering five historical periods 1900-1909, 1910-1914, 1915-1919, 1920-1929, 1930-1939 (see
table 1), we expected a steady continuous decline in mortality risks in the subsequent periods with
the exception of World War I (1915-1918) and the epidemic of Spanish influence (1918-1919).
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Table 1 - Here
Results
Results of logistic regression analysis are presented in three different models in table 2. Model 1
assumes as dependent variable the risk of perinatal mortality (stillbirths and early deaths within 6
days of delivery); model 2 takes into account the risk of late neonatal mortality (deaths between 7
and 30 days) and model 3 focuses on perinatal and neonatal mortality risk (stillbirths and deaths
within 30 days of delivery).
In model 3, related to the perinatal and neonatal mortality in the first month of life, bio-
demographic effects as multiple birth, sex and maternal age are significant. Parity effect is not
significant, probably because of the high proportion of unknown order childbirths. Considering
model 1 and 2 in more detail, multiple births appear extremely dangerous, since twins register
higher and significant odds ratio (9.3 for perinatal mortality in the first week, decreasing to 6.7 for
late neonatal death). Lower significant female risks are observed for the late neonatal period,
whereas newborns of older mothers significantly experience an increase in perinatal mortality risk
within 6 days after delivery.
As expected, periods affect perinatal mortality in both first week and first month after delivery
(model 1 and 3), with significantly declining risks. Confirming the expected results, higher perinatal
mortality risk is found on winter. Considering late neonatal life (model 2), season effects are not
significant and only the two decades after the first world war show a significant declining odds
ratio.
Turning to the socio-economic determinants, newborns of mother involved in agriculture
experience a 44 per cent higher perinatal mortality risk in the first month of life. With respect to the
socio-economic status of the father, well off and higher status group has a 65 per cent lower
probability of perinatal mortality within 6 days of birth than rural daily wagers (model 1), whereas
sharecroppers and farmers have a 46 per cent significant reduction only in late neonatal mortality
19
risk (model 2). It is likely that well off could rely on better antenatal and obstetrical care in early
perinatal life, whereas multiple sharecroppers’ household could provide better protection during the
late neonatal life. No significant effect results for father’s literacy, whereas “father not present”
category significantly increases the late neonatal mortality risk. The presence of the father could
make the difference only after the first week of life, since it appears less important during and
immediately after childbirth, when bio-demographic determinants prevail.
Looking at the death clustering measures, the median odds ratio of late neonatal model (2) are twice
lower than those calculated for the perinatal model (1). In these terms, the existence of “higher
mortality risk mothers” appears more related to the perinatal period that includes stillbirths and
deaths within 6 days of delivery.
Table 2 - Here
In order to show how perinatal deaths clustering could vary between different social groups, table 3
includes death clustering measures from three separated logistic regression models of perinatal and
neonatal mortality risk in the first month of life, referred to the father profession: sharecroppers and
farmers (model 4), rural daily wagers (model 5) and other workers (model 6).
Table 3 - Here
Sharecroppers and farmers’ median odds ratio (MOR) is clearly lower than that referring to rural
daily wagers and to other workers. This means that mothers in sharecroppers’ and farmers’ families
had more homogenous perinatal mortality risks than mothers of other social groups. According to
these results, it was more likely to find higher risks mothers among daily wagers and other workers
groups, since the median odds ratio between high risk mothers and low risk ones in the
20
sharecroppers and farmers group is almost half of the values calculated for the other groups (1.9
against respectively 3.9 and 3.2). These findings suggest that the multiple sharecroppers’ household
could better help and protect the newborn children of high risk women, confirming the protecting
role of multiple households.
In table 4, the effects of the length of the interval from previous birth and maternal history are
presented including only newborns of second and higher parities and therefore excluding first and
unknown order childbirths.
Table 4 - Here
In late neonatal life from 7 to 30 days after delivery, the length of the interval from previous birth
and maternal history effects are not significant (model 8), whereas they are statistically significant
for mortality risks in the first week (model 7) and in the first month of life (model 9). During the
perinatal period (within 6 days of life), the intervals from previous birth from 18 to 30 months and
longer than 30 months induce a risk of dying lower than the reference interval (46 and 57 per cent
respectively). In addition, the birth interval effect on perinatal and neonatal mortality in the first
month follows a similar pattern.
The median odds ratio almost equal to 1 in model 8, suggests that late neonatal mortality risk for
second and higher order births is homogenous at the mother level. Conversely, when perinatal
mortality in the first week of life (model 7) is considered, clustering of perinatal deaths is 90 per
cent higher than late neonatal mortality.
In table 5 death clustering measures, maternal mortality and previous birth-interval effects are
estimated distinguishing by rural and non-rural female workers (models 10 and 11).
The length of previous birth-interval and maternal history effects follow the same patterns in both
models. However, the effect of maternal history on perinatal death risk is higher (2.2) and
significant among rural female workers, whereas only a birth interval longer than 30 months
21
appears significant among non-rural women. As in model 10 the median odds ratio is almost equal
to 1, there are no evidences of high risk mothers among non-rural working women. Conversely,
higher death clustering at the mother level is observed among women working in agriculture.
Table 5 - Here
In table 6, separated model are estimated by taking into account only childbirths of working
mothers in rural sector and distinguishing respectively between sharecroppers’ and daily wagers
wives. Only second and higher order childbirths have been here considered. As expected, the
highest measures of death clustering are found for daily wagers’ wives that worked in agriculture.
In sharecroppers’ families, measures of perinatal and neonatal mortality clustering are equal to
almost 1 and remain not relevant even for mothers involved in rural works.
Table 5 - Here
Conclusions
In our analysis, the effects of bio-demographic factors on both early perinatal and late neonatal
mortality are confirmed. Significantly higher risks for multiple-births and male newborns have been
found. Moreover maternal age older than 34 years is significantly associated with a higher risk of
perinatal mortality. Parity effect results to be statistically non-significant in both early perinatal
(stillbirths and deaths within 6 days of delivery) and late neonatal ages (deaths between 7 and 30
days of life), probably because of the high proportion of unknown birth orders.
As expected, significant higher perinatal risk has been found in winter. The historical period effect
on perinatal and neonatal mortality in the first month of life significantly declines in the two
decades after World War I.
22
A significant lower risk of death emerges for the well-off group in the early perinatal period,
probably because they could rely on better resources and could also access to better antenatal and
obstetrical care. Sharecroppers instead register the lowest risk during the late neonatal period, when
causes of death related to exogenous factors prevail. It is possible that, in sharecroppers’
households, assistance from other co-resident women could protect newborns by these causes of
deaths related to infectious diseases, maternal competence, and childrearing practices.
Maternal working conditions have significant effects only when stillbirths and neonatal death within
one month of delivery are jointly considered. In this case, newborns of working women in
agriculture show a significant higher mortality risk than newborns from non-working mothers,
confirming the detrimental effects of heavy and physical maternal work. It is possible that those
mothers could not stay far from the work fields for a period before or after delivery.
Father’s ability to sign has no statistically significant effect, probably because signature ability was
not a good proxy for education attainment in the first decades of the nineteenth century, when some
very poor people could just be able to make a simple signature, without possessing more knowledge
and information than illiterate individuals. Nevertheless, late neonatal mortality risk significantly
rises when father was not present, suggesting that the lack of the father support could significantly
affect newborns late neonatal mortality, more frequently related to exogenous causes.
In order to measure the level of perinatal and neonatal death clustering and detect the presence of
high risk women, we included in the logistic regression models a cluster random effect at mother
level and then calculated the median odds ratios. Death clustering is found to be more pronounced
for early perinatal mortality than for late neonatal mortality. In these terms, it appears that death
clustering phenomenon tends to be more related to events linked to delivery. Results obtained by
analyzing a subsample of childbirths with complete maternal reproductive history, show that birth
intervals shorter than 18 months significantly reduce the risk of stillbirth and neonatal death within
6 days of childbirths. We also find that maternal history of previous stillbirths and infant deaths is
significantly associated with higher perinatal mortality risks.
23
Looking at the death clustering measures at the mother level, it is interesting to note that a certain
level of unexplained heterogeneity still remains in all the presented models. According to our
theoretical framework, this unexplained variability should be related to some other unobserved
family characteristics, such as household structures and female conditions. Considering stillbirths
and neonatal deaths within 30 days of delivery, we estimated separated logistic regression models
by father’s profession. Concentration of perinatal deaths at the mother level results lower for
women living in sharecroppers’ families than for those living in rural daily wagers’ families. Since
rural proletarians used to live in nuclear families and sharecroppers in complex households, these
findings highlight the effects of the different household structures on perinatal and neonatal deaths’
clustering. Multiple households were able to reduce risk factors related to specific mother
characteristics, relying on a more stable domestic economy, material resources and reciprocal
supports between family members.
A higher level of perinatal and neonatal clustering has been found among women working in
agriculture. More fragile women in terms of genetics and physiology could be severely harmed by
heavy physical activity with direct consequences on fetal and neonatal health. More interestingly,
maternal activity in agriculture is associated to a higher level of death clustering only for working
women married to rural daily wagers. The combination of poor conditions, worse nutritional state
and necessity to carry out heavy physical work made some women more fragile than others. In case
of complications at childbirth or precarious health conditions of newborns, high risk women could
rely on limited institutional, collective, and familial protections.
Because of their precarious conditions, rural proletarians had to constantly move searching for a
new job, far away from their families. So daily wagers’ wives could count on a limited network of
female solidarity, since their relatives probably lived in other villages. In these terms, our findings
confirm and are coherent with the “nuclear hardship” theoretical paradigm (Laslett 1988).
In the same perspective, no mortality cluster is found among sharecroppers’ wives working in rural
activities, since fragile mothers could more frequently receive help from co-resident women thus
24
reducing the impact of their disadvantage. This help was directly given in terms of obstetrical
assistance at delivery and childrearing by other competent women that already had experienced or
assisted previous childbirths, involving the transmission of knowledge and skills in childcare.
Relatives’ support was also material, related to better nurturing, warm clothes availability and work
organization. It is highly possible that sharecroppers’ wives could avoid more demanding physical
task during pregnancy since their privileged position in the hierarchy of rural activities.
Our results suggest that intergenerational and horizontal solidarity active in large families played a
significant role in explaining perinatal and neonatal mortality patterns and clustering.
25
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Table 1 Descriptive statistics for variables included in the analysis: percentage distribution and
mean values
Sources: Births, Marriages and Deaths Registers of the Municipality of Granarolo
All parities Second and higher parities
Sex of newborn child (%)
Male (Ref.) 51.00 49.19
Female 49.00 50.81
Multiple births (%)
Single (Ref.) 97.09 97.55
Twins 2.91 2.45
Age of mother (%)
<25 26.25 18.14
25-29 (Ref.) 24.75 33.55
30-34 18.06 25.84
> 34 16.31 22.47
Unknown 14.64 -
Parity (%)
1 30.40 -
2-3 (Ref.) 30.20 68.07
4+ 14.13 31.93
Unknown 25.27 -
Interval since previuos birth (%)
< 18 months (Ref.) - 17.17
18-30 months - 41.30
>30 months - 41.53
Maternal history (mean) - 0.18
Season (%)
Winter (Ref.) 25.58 24.13
Spring 25.93 26.95
Summer 23.49 23.31
Autumn 25.01 25.70
Socio-economic Status (%)
Professionals, clerical and sales 5.49 4.75
Skilled and lower skilled workers 23.02 22.98
Farmers 47.64 50.99
Rural daily wagers (Ref.) 21.00 21.27
Unknown 2.85 -
Mother rural status (%)
Mother not in rural work (Ref.) 40.28 34.24
Mother in rural work 59.72 65.76
Father's ability to sign (%)
Sign (Ref.) 81.76 82.19
No sign 12.10 11.86
Father not present 6.14 5.95
Period (%)
1900-1909 (Ref.) 30.30 26.58
1910-1914 15.43 17.26
1915-1919 10.23 12.55
1920-1929 25.44 26.77
1930-1939 18.61 16.84
No. of childbirths (twins=1) 4,918 2,167
35
Table 2 Logistic regression analysis of the risk of perinatal and neonatal mortality in Granarolo, 1900-1939
Sources: As table 1.
Odds Ratio SE p Odds Ratio SE p Odds Ratio SE p
Sex of newborn child
Male (Ref.) 1.000 - - 1.000 - - 1.000 - -
Female 0.875 0.129 0.367 0.384 0.093 0.000 0.678 0.087 0.003
Multiple births
Single (Ref.) 1.000 - - 1.000 - - 1.000 - -
Twins 9.258 2.660 0.000 6.691 2.441 0.000 9.976 2.575 0.000
Age of mother
<25 1.420 0.324 0.124 1.456 0.521 0.294 1.446 0.287 0.064
25-29 (Ref.) 1.000 - - 1.000 - - 1.000 - -
30-34 1.059 0.266 0.818 1.881 0.677 0.079 1.308 0.277 0.205
> 34 1.769 0.446 0.024 1.298 0.537 0.528 1.634 0.363 0.027
Unknown 1.593 0.571 0.194 1.797 0.851 0.216 1.628 0.493 0.107
Parity
1 1.096 0.218 0.643 1.244 0.382 0.478 1.143 0.197 0.439
2-3 (Ref.) 1.000 - - 1.000 - - 1.000 - -
4+ 1.017 0.260 0.948 0.989 0.397 0.978 1.023 0.228 0.920
Unknown 0.967 0.280 0.907 1.294 0.493 0.498 1.098 0.270 0.703
Season
Winter (Ref.) 1.000 - - 1.000 - - 1.000 - -
Spring 0.641 0.129 0.027 0.570 0.174 0.066 0.595 0.104 0.003
Summer 0.663 0.137 0.046 0.666 0.202 0.180 0.628 0.112 0.009
Autumn 0.601 0.124 0.013 0.651 0.192 0.145 0.591 0.104 0.003
Socio-economic Status
Professionals, clerical and sales 0.341 0.184 0.047 0.886 0.497 0.830 0.498 0.202 0.086
Skilled and lower skilled workers 0.837 0.236 0.529 1.084 0.416 0.833 0.864 0.207 0.542
Sharecroppers and Farmers 0.901 0.181 0.603 0.539 0.150 0.026 0.750 0.130 0.096
Rural daily wagers (Ref.) 1.000 - - 1.000 - - 1.000 - -
Unknown 0.557 0.336 0.333 1.227 0.712 0.725 0.765 0.338 0.545
Mother rural status
Mother not in rural work (Ref.) 1.000 - - 1.000 - - 1.000 - -
Mother in rural work 1.372 0.289 0.133 1.734 0.540 0.077 1.442 0.262 0.044
Father's literacy
Sign (Ref.) 1.000 - - 1.000 - - 1.000 - -
No sign 0.857 0.208 0.527 0.928 0.321 0.830 0.880 0.185 0.542
Father not present 1.282 0.453 0.482 2.216 0.904 0.051 1.619 0.454 0.086
Period
1900-1909 (Ref.) 1.000 - - 1.000 - - 1.000 - -
1910-1914 0.825 0.182 0.383 0.873 0.289 0.681 0.845 0.162 0.381
1915-1919 0.588 0.170 0.067 0.661 0.272 0.315 0.615 0.152 0.049
1920-1929 0.523 0.115 0.003 0.705 0.209 0.237 0.559 0.104 0.002
1930-1939 0.398 0.104 0.000 0.426 0.163 0.026 0.391 0.088 0.000
Sigma u 1.169 0.445 1.047
Rho 0.294 0.057 0.250
MOR 3.053 1.529 2.717
Number of events 241 92 333
Number of childbirths 4,918 4,676 4,918
Number of mothers 2,164 2,127 2,164
Log likelihood -888.1 -416.1 -1122.8
Stillbirths + Deaths 0-6 days Deaths 7-30 days Stillbirths + Deaths 0-30 days
Model 1 Model 2 Model 3
36
Table 3 Sigma u, Rho and MOR from logistic regression analysis of the risk of perinatal and neonatal
mortality by fathers’ professions in Granarolo, 1900-1939. Stillbirths and deaths within 30 days of delivery
are considered
Note: The models also include the following control variables: SES, Mother rural status, Father's literacy,
Age of mother, Parity, Multiple births, Sex of newborn child, Seasonality, and Period.
Sources: As table 1.
Table 4 Logistic regression analysis of the risk of perinatal and neonatal mortality in Granarolo including
interval births, parity and maternal history, 1900-1939. Second and higher parities are considered
Note: The models also include the following control variables: SES, Mother rural status, Father's literacy,
Age of mother, Parity, Multiple births, Sex of newborn child, Seasonality, and Period.
Sources: As table 1.
Model 4 Model 5 Model 6
Sharecroppers and Farmers Rural daily wagers Other workers
Sigma u 0.665 1.450 1.255
Rho 0.118 0.390 0.324
MOR 1.886 3.992 3.312
Number of events 155 93 76
Number of childbirths 2,343 1,033 1,402
Number of mothers 977 506 746
Log likelihood -523.4 -276.6 -265.7
Odds Ratio SE p Odds Ratio SE p Odds Ratio SE p
Interval since previuos birth
< 18 months (Ref.) 1.000 - - 1.000 - - 1.000 - -
18-30 months 0.537 0.150 0.026 0.916 0.435 0.853 0.596 0.142 0.030
>30 months 0.431 0.132 0.006 0.659 0.357 0.442 0.465 0.123 0.004
Maternal history 1.879 0.462 0.010 1.866 0.715 0.104 1.990 0.400 0.001
Sigma u 0.645 0.005 0.007
Rho 0.112 0.000 0.000
MOR 1.851 1.005 1.006
Number of events 101 33 134
Number of childbirths 2,167 2,066 2,167
Number of mothers 950 933 950
Log likelihood -373.8 -152.7 -464.7
Stillbirths + Deaths 0-6 Deaths 7-30 Stillbirths + Deaths 0-30
Model 7 Model 8 Model 9
37
Table 5 Logistic regression analysis of the risk of perinatal and neonatal mortality by mothers' rural status in
Granarolo, 1900-1939. Stillbirths and deaths within 30 days of delivery of second and higher parities are
considered
Note: The models also include the following control variables: SES, Mother rural status, Father's literacy,
Age of mother, Parity, Multiple births, Sex of newborn child, Seasonality, and Period.
Sources: As table 1.
Table 6 Sigma u, Rho and MOR from logistic regression analysis of the risk of perinatal and neonatal
mortality for only childbirths of mothers in rural sector by father’s rural professions. Granarolo, 1900-1939.
Stillbirths and deaths within 30 days of delivery are considered
Note: The models also include the following control variables: SES, Mother rural status, Father's literacy,
Age of mother, Parity, Multiple births, Sex of newborn child, Interval since previous birth, Maternal History,
Seasonality, and Period.
Sources: As table 1.
Odds Ratio SE p Odds Ratio SE p
Interval since previuos birth
< 18 months (Ref.) 1.000 - - 1.000 - -
18-30 months 0.496 0.240 0.148 0.656 0.190 0.146
>30 months 0.243 0.132 0.009 0.560 0.180 0.071
Maternal history 1.360 0.661 0.527 2.188 0.530 0.001
Sigma u 0.003 0.516
Rho 0.000 0.075
MOR 1.003 1.637
Number of events 33 101
Number of childbirths 742 1,425
Number of mothers 437 651
Log likelihood -118.5 -332.4
Model 10 Model 11
Non rural sector Rural sector
Model 12 Model 13
Sharecroppers and Farmers Rural daily wagers
Sigma u 0.160 1.120
Rho 0.008 0.276
MOR 1.165 2.912
Number of events 62 31
Number of childbirths 980 376
Number of mothers 437 177
Log likelihood -211.8 -89.6