Delivery of Twin Gestations

7/31/2019 Delivery of Twin Gestations

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Additional smaller series have confirmed these findings. The lowest perinatal mortality for twin

pregnancy appears to be at 37 to 38 weeks of gestation [5,7-15]; however, these studies have notexcluded all complicated pregnancies. Furthermore, in some studies delivery before 38 weeks

was associated with higher neonatal morbidity than later delivery [11,16,17]. Therefore, in

uncomplicated pregnancies and when the twins are continuing to grow and mature, we and

others feel it is reasonable to deliver at or after 38 completed weeks of gestation to minimize thefrequency of neonatal complications [16-19]. However, there is no consensus on the optimum

time to deliver these pregnancies. Some experts have argued for delivery of

monochorionic/diamniotic twins as early as 32 to 36 weeks of gestation and delivery ofmonochorionic twins earlier than dichorionic twins [20-23].

The only randomized trial that tried to determine whether delivery at 37 weeks resulted in better

outcomes than later delivery had too few patients (n = 36) to detect significant differences [24].

Assessment of pulmonary maturityAlthough there is widespread belief that fetuses oftwin gestations experience more rapid pulmonary maturation than singleton fetuses [25],

this assertion has been challenged by conflicting data [26-28]. The potential for neonatalrespiratory problems is particularly important when considering the optimal timing ofdelivery of twins since many of these pregnancies are delivered by cesarean birth prior to

the onset of labor [29,30].

As with singletons, there appears to be a significant risk of respiratory problems in late preterm

twins:

- One study evaluated the prevalence of neonatal respiratory disorders in the infants of126 women with twins who underwent elective cesarean delivery before labor (at 36 to

40 weeks of gestation) [2]. The majority (65 percent) of cesarean deliveries were

performed due to malpresentation in one or both fetuses; there were no maternal or fetalcomplications (eg, severe preeclampsia, fetal growth restriction) requiring medically

indicated delivery. Neonatal respiratory disorders occurred frequently, and more often

among infants born at 36 to 37 compared to 38 or more weeks of gestation (13 versus 2percent).

- In another series of twins delivered by the vaginal or abdominal route, the prevalence ofrespiratory morbidity at 36 to 37 weeks was 23 percent, compared to 7 percent at 37 to 38weeks [31].

Therefore, fetal pulmonary maturity should be evaluated if elective early delivery is planned.

Some authors, including ourselves, feel that amniocentesis of only one twin is adequate if the

gestation is 36 weeks [25,32], but others test both twins in all cases because pulmonary

maturity can be asynchronous [33].

Based on review of these data [2,32,33], the American College of Obstetricians and

Gynecologists suggested amniocentesis before elective delivery of twins less than 38 and 0/7thsweeks of gestation [34]. They state that amniocentesis of only one twin is generally sufficient at

a gestational age 33 and 0/7ths weeks since discordancy is uncommon at this time [32,33], but

they suggest amniocentesis of both twins when the procedure is performed earlier in pregnancy.
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When only one sac is sampled, it would be reasonable to sample the sac of the fetus less likely to

be mature. As an example, a non-presenting, larger, male fetus would be less likely to haveachieved lung maturity than a smaller, presenting female fetus. (See"Assessment of fetal lung

maturity".)

Upper gestational age limitIn the rare twin pregnancy in which labor has not occurredby 40 weeks of gestation and no fetal or maternal indications for delivery are present, we

electively intervene to deliver the twins. There are few studies evaluating the uppergestational age limit for allowing a twin pregnancy to remain undelivered. One such

series included over 60,000 twin pairs delivered at 37 or more weeks of gestation [19].

The odds of neonatal death (unrelated to congenital anomalies) significantly increased at

40 weeks compared with 37 weeks of gestation (OR 4.24, 95% CI 2.65-7.00).

Monoamniotic twin pregnancyAdditional issues must be addressed in timing the delivery of a

monoamniotic twin pregnancy. Delivery earlier in the third trimester may be indicated becauseof the high rate of perinatal mortality described in these pregnancies despite intensive fetal

surveillance, (30 to 70 percent, which is likely due to cord entanglement) [35,36]. Managementof monoamniotic twin pregnancy is discussed in detail separately. (See"Monoamniotic twinpregnancy".)

ROUTEThe presentation and, in some situations, the gestational age of twins can influencethe selection of vaginal versus cesarean delivery.

Should routine cesarean delivery be offered?Cesarean delivery is common in twin

pregnancies: over 60 percent of twin births are by cesarean [37]. Some investigators have

proposed that neonatal outcome could be improved by a policy of routine cesarean delivery for

all twin pregnancies. The basis for this proposal is concern that the relative risk of anoxic death

of the second twin is increased as a result of mechanical problems (eg, compound presentation,cord prolapse, abruptio placentae) after vaginal birth of the first twin [38]; this is most significant

in gestations 36 weeks [39]. However, others have pointed out that even though the relative risk

of neonatal mortality may be increased, the absolute risk remains low and, therefore, a largenumber of cesareans would have to be done to prevent one death of a second twin [40].

We do not believe that there is adequate evidence to support a policy of routine cesarean delivery

of twin pregnancies, although data are limited. The best evidence comes from a systematic

review of four studies (one randomized trial and three cohort studies) including almost 1000 twinpregnancies [41]. This analysis did not find a statistically significant difference in perinatal or

neonatal mortality for twins delivered after planned cesarean delivery compared to those

delivered after a trial of labor (planned vaginal delivery) (odds of death after cesarean 2.06, 95%

CI 0.29-14.66 trend favors vaginal delivery). Planned cesarean delivery was also associated witha higher rate of neonatal respiratory problems, such as transient tachypnea [41,42]. Given the

wide confidence interval, this analysis is clearly inadequate for conclusively determining which

route of delivery should be offered.
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Better data on which to base a recommendation for the optimal route of delivery for twins will be

provided by the Twin Birth Study, an ongoing international trial of 2400 twin pregnanciesrandomly assigned to deliver vaginally or by cesarean.

We do not favor a policy of planned cesarean delivery of all twin pregnancies. With appropriate

intrapartum monitoring and management (see below), the second twin is not at high risk ofneonatal mortality or morbidity [43]. We choose a delivery route based upon presentation,

gestational age, and amnionicity (see below), as well as the presence/absence of standardobstetrical indications for cesarean delivery (eg, placenta previa).

Should VLBW fetuses be delivered by cesarean?Some investigators have suggested thatcesarean delivery may decrease the risk of intracranial hemorrhage in very low birth weight

(VLBW) preterm twin fetuses, regardless of presentation [44,45]. We and others have not found

adequate evidence to recommend a policy of elective cesarean delivery of VLBW babies [46].

(See"Intrapartum management of the low birthweight fetus".)

Effect of fetal presentation

Vertex-vertex twinsThis presentation accounts for approximately 42 percent of twins [47].

The general consensus is that a trial of labor with the goal of a vaginal delivery of vertex-vertextwins is appropriate at any gestational age [3,48].

Nonvertex presenting twinA nonvertex first twin comprises approximately 20 percent of twinpresentations. A unique, potential complication of breech-vertex twin delivery, as opposed to

breech singleton delivery, is the possibility of interlocking chins (ie, locked twins), but this is

rare.

A retrospective case-control analysis of data from 13 centers that allowed vaginal birth forbreech first twins reported no difference in Apgar scores and neonatal mortality related to routeof delivery among infants weighing more than 1500 grams [49]. However, nonvertex presenting

fetuses weighing less than 1500 grams that were delivered vaginally had significantly higher

rates of low Apgar scores and neonatal mortality compared to those delivered by cesarean (37versus 20 percent and 45 versus 8 percent, respectively).

In contrast to this report, we and others suggest cesarean delivery when the first twin is not in thevertex presentation because the safety of vaginal delivery in these cases has not been confirmed

by randomized trials and the general consensus in the obstetric community is against vaginal

delivery of the breech presenting fetus, even in singleton pregnancies [48]. (See"Delivery of the

fetus in breech presentation".) An exception is the breech presenting second twin (see below).

Vertex-nonvertex twinsOptions for delivery of vertex-nonvertex twins (38 percent of twins)

include cesarean delivery of both twins, vaginal delivery with cephalic version of the secondtwin, or vaginal delivery with breech extraction of the second twin.

The only randomized trial of planned vaginal versus abdominal birth for vertex-nonvertex twins

included 60 women with otherwise uncomplicated pregnancies at 35 to 42 weeks of gestation
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[50]. Maternal morbidity was higher with planned cesarean delivery, with no difference in

neonatal outcome. However, this trial was too small to detect clinically important differences inoutcome between the two groups.

Many studies have reported successful vaginal delivery of both twins using internal or external

version or breech extraction of the second twin [51-67]. The second twins of vertex-nonvertexand vertex-vertex pairs generally had similar neonatal outcomes irrespective of mode of delivery

or procedures performed during delivery, but these series were small and observational.Successful vaginal delivery appeared to be less likely when external version was attempted than

when breech extraction was performed immediately after delivery of the presenting twin

[53,54,61,65]; external version was completed in 40 to 50 percent of cases (the remainder weredelivered by cesarean delivery), while breech extraction followed by vaginal birth succeeded in

96 to 100 percent of patients [53,54]. Of note, the mean gestational age was approximately 34 to

35 weeks and the mean birthweight was 2100 to 2200 grams in these studies; 7 to 15 percent of

the neonates weighed less than 1500 grams.

In contrast, a population based cohort study of twin deliveries in the United States reportedinfants 1500 to 4000 grams had a significantly higher frequency of neonatal death (adjusted foranomalies), asphyxia, and injury when both twins of a vertex-nonvertex pair were delivered

vaginally than when both twins were delivered by cesarean [68]. Interpretation of these data is

limited because it was obtained from birth certificates.

In the absence of good data favoring one approach over another, we suggest offering the patient

an attempt at breech extraction of the second twin and proceeding to cesarean delivery ifunsuccessful. If the patient does not wish to attempt breech extraction of the second twin, we

give her the option of attempting external cephalic version of the second twin or undergoing

cesarean delivery of both twins. When discussing the options of breech extraction or external

cephalic version with patients, the obstetrician should include information about his or herexperience and comfort with these procedures. Many obstetricians, based on training and

experience, may feel more comfortable performing cesarean delivery. Under these

circumstances, cesarean delivery of both twins is recommended.

Contraindications to breech extractionWe generally do not offer the option of breechextraction when:

(1) The estimated fetal weight of the second twin is 20 percent more than that of thepresenting twin.

(2) The delivery of the presenting twin suggests that the pelvis may not be adequate for a

breech delivery, such as when there is a prolonged second stage or marked molding of the head.

(3) The gestational age is less than 28 weeks or the estimated fetal weight of the second twin is

less than 1500 grams. Under these circumstances, we recommend performing cesarean deliveryof both twins, rather than attempting cephalic version of the nonvertex second twin.
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Trial of labor after previous cesarean deliveryThere are insufficient data to establish the

safety of attempting vaginal birth of twins after a previous low transverse cesarean delivery.Available data are reassuring that outcomes are similar to those in women with singletons

undergoing a trial of labor. One of the largest series reported uterine rupture in 16 of 1850

women with twins (0.9 percent) undergoing a trial of labor after previous cesarean delivery; this

rate was comparable to that in singleton pregnancies undergoing trial of labor (0.8 percent) [69].Successful vaginal delivery was achieved in 45 percent of the twin gestations and 62 percent of

the singletons. Smaller series have reported similar findings [70-76]. (See"Trial of labor after

cesarean delivery".)

It is our practice to offer a trial of labor to women with twin pregnancies and one prior cesareandelivery, provided they go into spontaneous labor. Because the most common initial sign of

uterine rupture is fetal heart rate changes, we continually monitor both fetuses. If this is not

technically possible, then cesarean delivery is performed.

Monoamniotic twinsThe route of delivery of monoamniotic twins is considered separately.

(See"Monoamniotic twin pregnancy".)

MANAGEMENT

LaborIt is not clear whether multiple gestation has an effect on the progress of labor; studies

have reported conflicting results [77,78].Oxytocinfor augmentation or induction of laborappears to be effective; there are inadequate data to allow evaluation of safety [79-82].

Electronic fetal heart rate monitoringMultiple gestations are at increased risk of intrapartum

complications; therefore, we monitor both twins continuously during labor. Intermittentauscultation is not practical and may not reliably distinguish one twin from the other.

The fetal heart rate of each twin can be monitored using a single machine (figure 1). These ratesare often synchronous, thus requiring frequent careful review of the tracing to make sure each

fetus' heart rate is being monitored. Ultrasound can assist in ensuring that both fetal heart rates

are traced. If separate monitors are used, internal clocks must be synchronized, paper speedsmust be identical, and contractions must be displayed on both tracings.

Electronic fetal heart rate monitoring is particularly useful for assessing the well-being of thesecond twin during the high risk period after delivery of the first twin (see 'Interval between

delivery of the two twins'below).

Analgesia and anesthesiaEpidural analgesia/anesthesia is generally recommended because itprovides good pain relief, does not cause neonatal depression, and is a suitable anesthetic if

uterine manipulation (eg, version) or operative delivery (eg, forceps, cesarean) become

necessary.

First twinWhen vaginal birth is attempted, the capacity for immediate cesarean delivery isimportant in the event that complications necessitating urgent delivery arise (eg, prolapsed

umbilical cord, nonreassuring fetal heart rate, or failed breech extraction/cephalic version).
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Emergency cesarean delivery has been reported in 10 to 30 percent of pregnancies in which

vaginal births of twins had been planned, and may be necessary for delivery of the second twinafter vaginal birth of the first twin (see below). It is our practice to deliver all twin pregnancies in

an operating room where cesarean delivery can be performed. In our hospital, patients are moved

to the operating room in the second stage of labor. However, if a patient can be transported to an

operating room rapidly, delivery of vertex-vertex twins in a labor room is not unreasonable.

Delivery of the first twin of a diamniotic pair is similar to delivery of a singleton except theumbilical cords should be marked with progressive numbers of clamps (eg, one for the first twin

birth, two for the second twin birth). If surgical clamps are used initially, they should be replaced

with a like number of plastic umbilical cord clamps prior to sending the placenta for formalexamination. Recall that 'twin A' on ultrasound may not be first born at delivery (especially if the

delivery is by cesarean), and this infant is typically called 'baby A' by delivery room and nursery

personnel.

Second twinAfter delivery of the first twin, the heart rate and position of the second twin

should be evaluated using ultrasound and electronic fetal monitoring. If the second twin is in anonvertex presentation, ultrasound can be used to assist external cephalic version, breechextraction, or internal podalic version of the second twin, if necessary.

As discussed above, our preference is breech extraction if the second twin is not in a vertexpresentation and there are no contraindications to breech extraction (see'Vertex-nonvertex

twins'above). Intrauterine manipulation is aided by ultrasonographic visualization of the

orientation between the physician's hands and fetal parts (figure 2A-B)[83] and can be facilitatedby administering intravenousnitroglycerinor inhalational anesthesia, which relax uterine muscle

[84]. Effective maternal analgesia is also crucial. When the fetus is in the desired presentation for

delivery,oxytocinis given if labor has not resumed. Amniotomy can be performed after the

presenting part is engaged.

Others have taken a somewhat different approach. One historic cohort study of 130 planned

vaginal twin deliveries reported no patient who had a vaginal delivery of the first twin requiredcesarean delivery of the second twin [67]. In this group's practice, all patients who were

undelivered at 38 weeks of gestation underwent induction if they met strict criteria (estimated

weight of the second twin 1500 g and no more than 20 percent greater than the weight of thepresenting twin, absence of usual contraindications to vaginal delivery). After vaginal birth of

the first twin, the second twin was delivered as a vertex presentation if the vertex was engaged

immediately after delivery of the first twin, by breech extraction if in breech presentation after

delivery of the first twin, and by breech extraction after internal podalic version if in vertexpresentation but unengaged after delivery of the first twin. The authors attributed their success to

active management of the second stage of labor by obstetricians experienced in breech delivery

and internal version, and to their criteria for selecting candidates for vaginal delivery.

Interval between delivery of the two twinsHistorically, second born twins were reported to

have a higher incidence of adverse outcome (morbidity and mortality) due to lower birth weight;higher frequency of malpresentation, cord prolapse, and abruptio placentae; and more deliveries

involving internal podalic version. A prolonged interval between delivery of the first and second
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twins was also thought to be associated with poorer outcomes. Intervals of less than 25 to 30

minutes were advocated, and maneuvers such as internal podalic version or breech extraction ofthe second twin were often recommended to hasten delivery [85-87].

Subsequent studies undertaken after the universal routine use of electronic fetal monitoring

during labor suggest that there does not have to be a finite interval between delivery of the firstand second twin, as long as the fetal heart rate tracing is reassuring [88-90]. Electronic fetal

monitoring and the availability of real-time ultrasound have enabled obstetricians to identifythose second twins who would benefit from expedited delivery, while allowing most cases to be

managed expectantly [89]. Thus, spontaneous delivery of both twins is more likely to be

achieved.

Oxytocinaugmentation of labor after delivery of the first twin is reasonable and sometimes

necessary due to a temporary reduction in contraction frequency after the first birth [3].

Delayed-interval delivery in previable gestations is discussed separately. (See"Delayed-interval

delivery in multifetal pregnancy".)

Unplanned cesarean deliveryAn unplanned cesarean for delivery of the second twin is not

uncommon. This was illustrated by a population based cohort study of twin deliveries in theUnited States in which 9.5 percent of second twins were delivered by cesarean after vaginal birth

of the first twin [91]. The frequency of cesarean delivery of the second twin after vaginaldelivery of the first twin was lower (6.3 percent) if the second twin was vertex [92], but higher(24.8 percent) if only vertex-nonvertex live births were considered [68].

Although data from retrospective studies suggest the risk of adverse outcome is highest in secondtwins delivered by cesarean after vaginal birth of the first twin [68,93-95], data from a small

randomized trial [50] and a large prospective study [96] do not support these findings. Theremay, however, be an increased risk of maternal or neonatal infection due to exposure to labor

and ruptured membranes.

MONOZYGOTIC OR DIZYGOTIC?Approximately two-thirds of twins are dizygotic. It isof importance to parents and twins to know whether same sex twins are monozygotic (in lay

terms "identical"). Based upon a genotype and placental study of 668 consecutive twin pairs in

Birmingham, England, parents can be informed in the delivery room that 37 percent of all same

sex twins are "identical" [97]. Same sex twins are virtually always "identical" if monochorionic,while 18 percent of same sex twins with dichorionic membranes are "identical" (figure 3).

However, these proportions may not be accurate for pregnancies conceived through in vitro

fertilization, in which the rate of monozygotic twinning appears to be higher than in

spontaneously conceived pregnancies (2.3 versus 0.4 percent of pregnancies) [98]. In addition,there are two case reports of dizygotic twins with monochorionic placentation [99,100]. The

mechanism has not been explained, but may have been related to assisted reproductive

technology.

Zygosity can be determined conclusively using blood type or DNA markers [101].
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SUMMARY AND RECOMMENDATIONS

We suggest avoiding elective delivery of diamniotic twins prior to 38 weeks or after 40weeks of gestation (Grade 2C). (See'Timing'above.)

For vertex-vertex twins, we suggest vaginal delivery in the absence of standardindications for cesarean delivery (Grade 2C). (See'Vertex-vertex twins'above.)

When the first twin is not in vertex presentation, we suggest cesarean delivery (Grade2C). (See'Nonvertex presenting twin'above.)

For vertex-nonvertex twins, we suggest breech extraction of the second twin only if theobstetrician has the requisite experience and if the patient provides informed consent

(Grade 2C). (See'Vertex-nonvertex twins'above.)

Available data are reassuring that outcomes in women with twins attempting vaginal birthafter a previous cesarean delivery are similar to those with singletons undergoing a trialof labor. However, these data are insufficient to definitively establish that uterine rupture

rates are comparable. (See'Trial of labor after previous cesarean delivery'above.)

Oxytocinfor augmentation or induction of labor appears to be effective in twingestations; there are inadequate data to establish the safety of this intervention. (See'Labor'above.)

We suggest continuous electronic fetal monitoring of both fetuses during labor (Grade2C). (See'Electronic fetal heart rate monitoring'above.)

We suggest epidural analgesia/anesthesia during labor (Grade 2C). (See'Analgesia andanesthesia'above.)

After delivery of the first twin, the heart rate and position of the second twin should beevaluated using ultrasound and electronic fetal monitoring. As long as the fetal heart rate

tracing is reassuring, there is no duration of elapsed time from delivery of the first twin

that necessitates intervention to deliver the second twin. Six to 25 percent of second twinswill be delivered by cesarean after vaginal delivery of the first twin. (See 'Second

twin'above.)

Approximately 18 percent of same sex twins with dichorionic membranes are "identical."(see'Monozygotic or dizygotic?'above).
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Delivery of Twin Gestations

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