38 The March of Dines Birthyeight Standards
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302 SPO Abstracts 35 IN-VITRO COMPARISON OF FOUR TOCOLYTIC AGENTS, ALONE AND IN COMBINATION. a....IaskiII'. G. Saade '. M. BeHort', K. Moise. Depts. Ob/Gyn. Inonu University. Malatya. Turkey and Baylor College of Medicine. Houston. TX. OBJECTIVE: To compare the tocolytic effect of MgS04 (MS). ritodrine (R). (11. nifedipine (N). alone or in combination. on contracted myometrial s1Jips from pregnant (laboring and noolaboring) and noo-pregnant patients. STUDY DESIGN: Laboratory based irwitro study. Human myometrial strips were suspended in organ chambers. for isotonic measIKements. A maximal contraction was indoced witll KCt Myometrial strips from noo-pregnant patients were used to obtain cwnulative coocentratiOf1.respoose C\JlVeS for MS. R. T. N. M+ T. R+N. and M+R. The molar concentration causing 50% relaxation (lC,.! was determined for each dru&,combination. Myometrial strips from pregnant uteri (obtained at cesarean section from laboring and noolaboring patients) were then exposed to the same IC,. dru&,combination derived from the noo-pregnant tissue. Data was expressed in terms of the pO, (defined as IC,.!. Statistical analysis: ANOVA and Newman-Keuls test for single and repeated measurements; significance: p < 0.05. RESULTS: In tile first part (n=5). tile most effective single agent was N witll a pO, (4.38%0. 05) significantly higher tIlan R (3.35±0.0). T (3.l5±O.l2). or MS (1.67 At tile IC,. determined in tile first part and using strips from patients (n= 15). N caused similar relaxation in mm. (8.l±1.8) as R (7.9±2.0). and botll were more effective tIlan MS (6.7±1.l). or T (5.1±0.9). Combinations were significantly more effective tIlan single agents. witll R+N (15.7±1.6) being more effective tIlan M+T (14.4±1.2) which was more effective than M+R 'MIen strips from laboring patients were used (n= 15). the relaxations induced by MS (5. 85±1.6). N (5.6±1.l). R (4. 9±1.3) and T (3.l±I.06) were not significantly different results were found with M+T (8.6±1.7). R+N (7. 6±1.5) and M+R For each agent or the contraction inhibition was signifICantly less when strips from laboring patients were used CONCLUSIONS: Nifedipine. alone or in combination. relaxes myometrial strips from noo-pregnant and noolaboring patients more effectively than other agents currently in use. Myometrial strips obtained from laboring patients are however more resistant to inhibition. with none of tile agents being superior. 36 T-TYPE AND L-TYPE CALCIUM CHANNELS IN FRESHLY DISPERSED HUMAN UTERINE SMOOTH MUSCLE. Roger Young', Dept. Ob/Gyn, Med. Univ. SC, Charleston, SC. OBJECTIVE: The hypothesis is that two clearly defined SUbtypes of voltage activated calcium channels exist in human uterine smooth muscle cells, and the blocking effects of magnesium and nifedipine will be different on each type. STUDY DESIGN: Tissue biopsies of the upper margins of uterine incisions made for term Cesarean deliveries were used to obtain human tissue for electrophysiology studies. Isolated cells were obtained by collagenase digestion and were studied using the whole-cell patch clamp technique. The nystatin patch modification was used to minimize calcium current run- down. Magnesium and nifedipine were used as calcium channel blocking agents. RESULTS: T-type and L-type calcium currents identified llsing a series of ion substitution, channel blocking, and voltage inactivation experiments. Without any blocking agents, both T and L-type calcium channels are expressed. Magnesium at 8 mM blocked both types of currents; 10 nifedipine blocked L-type currents only. Using data subtraction techniques, current-voltage curves of each type current were obtained and found to be similar to those reported for smooth muscle from other tissues and species. CONCLUSION: Pregnant human uterine smooth muscle cells exhibit two subtypes of voltage activated calcium channels. Magnesium and nifedipine both block the L-type current. Magnesium, but not nifedipine, blocks the T-type current. January 1993 Am J Obstet Gynecol 37 DIURNAL AND GESTATIONAL PATTERNS OF UTERINE ACTIVITY IN NORMAL HUMAN PREGNANCY. T Moore, 1 lams, R Creasy, K BurauX, A Davidson x Depts of ObGyn, UC San Diego, Ohio St Univ, UT Houston. OBJECTIVES: I) define the 24 hour uterine activity profile in normal pregnancy and 2) correlate contraction frequency with physical activity and emotional stress diaries. METHODS : 109 low-risk gravidas · who delivered at term recorded uterine contractions for 24 hours twice weekly from 20-40 weeks gestational age (GA) using an ambulatory monitor and stress diary. Contractions per hour (CPH) were calculated for each hour of day and week of GA. RESULTS: 71 ,683 hours were analyzed. No contractions were recorded in 73% of hours and less than 4 CPH in 96%. Significant interindividual variability was noted. Contractions increased markedly with GA (95th%=1.3±O.5 (SD) CPH at 21-24 wks, 2.9± 1.0 at 28-32 wks, 4.9±1.7 at 38-40 wks, p< .OOOI). A strong clustering of CPH occurred at night, which became more pronounced after 24 wks (Night:Day at 21-24 wks=1.8:1 , 2.3:1 at 28-32 wks, 2.0:1 at 37-40 wks, p <.OO I). CPH were converted to percentiles (CPH%) to adjust for GA and time of day. Rest was associated with a fall in CPH% by 1.25±O.02 (SE). p<.OOOI , while coitus increased CPH% by 5.25±O.20 (p<. 05). No changes were noted with emotional stress. CONCLUSIONS: This study provides normative contraction data in uncomplicated pregnancy. A strong diurnal rhythm is present from 24 wks onward with 67% of contractions occurring at night. CPH increases with gestational age but rarely exceeds 3/hr before term. Physical activity has a small but measurable effect on contraction frequency. 38 THE IWICH Of DIMES BIRTIllEIGHT STANDARDS . S. Cliver: R. Goldenberg, S. Entman, S. Baker, R. Copper: R. Davis. R. Creasy. Dept. Ob-Gyn, Univ. of Alabama at Birmingham & UTHSC. Houston TX. OBJECTIVE: To create a new set of "fetal growth standards" based on a population with well defined gestational ages (GAl and compare these standards to those previ ous 1 y pub 1i shed. METHODS : The data for the analysis were derived from 32,971 women deli veri ng ali veborn si ng1 eton at 5 centers from 1982-1986 during the data collection pha se of the March of Dimes Prematurity Prevention Trial. The population was 35% white. 46% black, 17% hispanic, and 8.9% of the births occurred at <37 wks. GA was based on all obstetric and neonatal data available including LMP, ultrasound, and Dubowitz examination. If significant discrepancies occurred, the GA was assigned by the prinCipal investigator. RESULTS : These standards differ in several ways from those pub 1 i shed previously by Lubchenko. Brenner. and IIi 11 i ams. In general , the 10th and 50th birthweight (BIIT) percentiles are lower at earlier GA·s. and are higher at term and post term. At >41 week s , the BIIT at the 10th and 50th percentiles continue to -;:ise. The BIiT's at the 90th percentile are far lower at earlier GA's than those in the other standards . At <37 wks, there is 1 itt 1 e di fference in the BIIT percent i 1 es by race. However, in term infants, the 10th and 50th percentile BIIT's are higher for Hispanic infants and lower for black infants compared to whites. The BIIT percentiles for females are consistently lower than for males . lIith major anomalies excluded. the BIiT's at the 10th and 50th percentiles in <37 wk infants differ by only 5-IOg with no apparent change at term . However, if smokers are excluded, the BlIT's at the lOth and 50th percent i 1 es increase by 50 to 80g . COIIClUSIOll: Prospectively correcting LHP GA with obstetric and neonatal data appears to shift infants previously categorized as both preterm and post-term to term . This s hift sharply decreases the preterm 90th percenti 1es and to a lesser degree the 10th and 50th percentiles. The BIIT percentiles for post term infants rise, apparently because previously misc1a ss ified lower birthweight term infants are now appropriately class ified.
Transcript of 38 The March of Dines Birthyeight Standards
302 SPO Abstracts
35 IN-VITRO COMPARISON OF FOUR TOCOLYTIC AGENTS, ALONE AND IN COMBINATION. a....IaskiII'. G. Saade '. M. BeHort', K. Moise. Depts. Ob/Gyn. Inonu University. Malatya. Turkey and Baylor College of Medicine. Houston. TX. OBJECTIVE: To compare the tocolytic effect of MgS04 (MS). ritodrine (R). terbuta~ne (11. nifedipine (N). alone or in combination. on contracted myometrial s1Jips from pregnant (laboring and noolaboring) and noo-pregnant patients. STUDY DESIGN: Laboratory based irwitro study. Human myometrial strips were suspended in organ chambers. for isotonic measIKements. A maximal contraction was indoced witll KCt Myometrial strips from noo-pregnant patients were used to obtain cwnulative coocentratiOf1.respoose C\JlVeS for MS. R. T. N. M+ T. R+N. and M+R. The molar concentration causing 50% relaxation (lC,.! was determined for each dru&,combination. Myometrial strips from pregnant uteri (obtained at cesarean section from laboring and noolaboring patients) were then exposed to the same IC,. dru&,combination derived from the noo-pregnant tissue. Data was expressed in terms of the pO, (defined as ~og IC,.!. Statistical analysis: ANOVA and Newman-Keuls test for single and repeated measurements; significance: p < 0.05. RESULTS: In tile first part (n=5). tile most effective single agent was N witll a pO, (4.38%0.05) significantly higher tIlan R (3.35±0.0). T (3.l5±O.l2). or MS (1.67 ±0.6~ At tile IC,. determined in tile first part and using strips from no~aboring patients (n= 15). N caused similar relaxation in mm. (8.l±1.8) as R (7.9±2.0). and botll were more effective tIlan MS (6.7±1.l). or T (5.1±0.9). Combinations were significantly more effective tIlan single agents. witll R+N (15.7±1.6) being more effective tIlan M+T (14.4±1.2) which was more effective than M+R (11.4±1.9~
'MIen strips from laboring patients were used (n= 15). the relaxations induced by MS (5.85±1.6). N (5.6±1.l). R (4.9±1.3) and T (3.l±I.06) were not significantly different Sim~ar results were found with M+T (8.6±1.7). R+N (7.6±1.5) and M+R (7.l±1.2~ For each agent or cornbin~tion. the contraction inhibition was signifICantly less when strips from laboring patients were used CONCLUSIONS: Nifedipine. alone or in combination. relaxes myometrial strips from noo-pregnant and noolaboring patients more effectively than other agents currently in use. Myometrial strips obtained from laboring patients are however more resistant to inhibition. with none of tile agents being superior.
36 T-TYPE AND L-TYPE CALCIUM CHANNELS IN FRESHLY DISPERSED HUMAN UTERINE SMOOTH MUSCLE. Roger Young', Dept. Ob/Gyn, Med. Univ. SC, Charleston, SC. OBJECTIVE: The hypothesis is that two clearly defined SUbtypes of voltage activated calcium channels exist in human uterine smooth muscle cells, and the blocking effects of magnesium and nifedipine will be different on each type. STUDY DESIGN: Tissue biopsies of the upper margins of uterine incisions made for term Cesarean deliveries were used to obtain human tissue for electrophysiology studies. Isolated cells were obtained by collagenase digestion and were studied using the whole-cell patch clamp technique. The nystatin patch modification was used to minimize calcium current rundown. Magnesium and nifedipine were used as calcium channel blocking agents. RESULTS: T-type and L-type calcium currents identified llsing a series of ion substitution, channel blocking, and voltage inactivation experiments. Without any blocking agents, both T and L-type calcium channels are expressed. Magnesium at 8 mM blocked both types of currents; 10 ~M nifedipine blocked L-type currents only. Using data subtraction techniques, current-voltage curves of each type current were obtained and found to be similar to those reported for smooth muscle from other tissues and species. CONCLUSION: Pregnant human uterine smooth muscle cells exhibit two subtypes of voltage activated calcium channels. Magnesium and nifedipine both block the L-type current. Magnesium, but not nifedipine, blocks the T-type current.
January 1993 Am J Obstet Gynecol
37 DIURNAL AND GESTATIONAL PATTERNS OF UTERINE ACTIVITY IN NORMAL HUMAN PREGNANCY. T Moore, 1 lams, R Creasy, K BurauX, A Davidsonx Depts of ObGyn, UC San Diego, Ohio St Univ, UT Houston. OBJECTIVES: I) define the 24 hour uterine activity profile in normal pregnancy and 2) correlate contraction frequency with physical activity and emotional stress diaries. METHODS: 109 low-risk gravidas · who delivered at term recorded uterine contractions for 24 hours twice weekly from 20-40 weeks gestational age (GA) using an ambulatory monitor and stress diary. Contractions per hour (CPH) were calculated for each hour of day and week of GA. RESULTS: 71,683 hours were analyzed. No contractions were recorded in 73% of hours and less than 4 CPH in 96%. Significant interindividual variability was noted. Contractions increased markedly with GA (95th%=1.3±O.5 (SD) CPH at 21-24 wks, 2.9± 1.0 at 28-32 wks, 4.9±1.7 at 38-40 wks, p<.OOOI). A strong clustering of CPH occurred at night, which became more pronounced after 24 wks (Night:Day at 21-24 wks=1.8:1 , 2.3:1 at 28-32 wks, 2.0:1 at 37-40 wks, p<.OO I) . CPH were converted to percentiles (CPH%) to adjust for GA and time of day. Rest was associated with a fall in CPH% by 1.25±O.02 (SE). p<.OOOI , while coitus increased CPH% by 5.25±O.20 (p<.05). No changes were noted with emotional stress. CONCLUSIONS: This study provides normative contraction data in uncomplicated pregnancy. A strong diurnal rhythm is present from 24 wks onward with 67% of contractions occurring at night. CPH increases with gestational age but rarely exceeds 3/hr before term. Physical activity has a small but measurable effect on contraction frequency.
38 THE IWICH Of DIMES BIRTIllEIGHT STANDARDS . S. Cliver: R. Goldenberg, S. Entman, S. Baker, R. Copper: R. Davis. R. Creasy. Dept. Ob-Gyn, Univ. of Alabama at Birmingham & UTHSC. Houston TX. OBJECTIVE: To create a new set of "fetal growth standards" based on a population with well defined gestational ages (GAl and compare these standards to those previ ous 1 y pub 1 i shed. METHODS : The data for the analysis were derived from 32,971 women deli veri ng ali veborn si ng1 eton at 5 centers from 1982-1986 during the data collection phase of the March of Dimes Prematurity Prevention Trial. The population was 35% white. 46% black, 17% hispanic, and 8.9% of the births occurred at <37 wks. GA was based on all obstetric and neonatal data available including LMP, ultrasound, and Dubowitz examination. If significant discrepancies occurred, the GA was assigned by the prinCipal investigator. RESULTS : These standards differ in several ways from those pub 1 i shed previously by Lubchenko. Brenner. and IIi 11 i ams. In general , the 10th and 50th birthweight (BIIT) percentiles are lower at earlier GA·s. and are higher at term and post term. At >41 weeks , the BIIT at the 10th and 50th percentiles continue to -;:ise. The BIiT's at the 90th percentile are far lower at earlier GA's than those in the other standards . At <37 wks, there is 1 itt 1 e di fference in the BIIT percent i 1 es by race. However, in term infants, the 10th and 50th percentile BIIT's are higher for Hispanic infants and lower for black infants compared to whites. The BIIT percentiles for females are consistently lower than for males . lIith major anomalies excluded. the BIiT's at the 10th and 50th percentiles in <37 wk infants differ by only 5-IOg with no apparent change at term. However, if smokers are excluded, the BlIT's at the lOth and 50th percent i 1 es increase by 50 to 80g . COIIClUSIOll: Prospectively correcting LHP GA with obstetric and neonatal data appears to shift infants previously categorized as both preterm and post-term to term . This shift sharply decreases the preterm 90th percenti 1es and to a lesser degree the 10th and 50th percentiles. The BIIT percentiles for post term infants rise, apparently because previously misc1ass ified lower birthweight term infants are now appropriately class ified.
