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438 SPO Abstracts

ABNORMAL FETAL GROWTH IN T\lIN GESTATION. Y. Barnhard', H.Y. Divan. Albert Einstein College of Medicine, Bronx, N,Y. OBJECTIVE: To identify the incidence of abnormal fetal growth in twin gestation. STUDY DESIGN: 190 consecutive twin pairs were divided into appropriate for gestational age (AGA) , small for gestational age (SGA i.e., birthweight <10th%), and large for gestational age (LGA i. e .. bi rthwei ght >90th%). Consi stent with the not i on that multiple gestation ;s a deviation from the human norm, a si ng1 etan rather than tw; n growth curve was used to evaluate fetal growth. The mean arterial pressure (HAP). hematocrit (HCT), prep regnancy weight (PPW), weight gain in pregnancy (WGP), gestational age at del ivery (GA), placental weight (PW), chorionicity (Cl. birthweight percentile for gestational age (Bw%) , the presence of preeclampsia (P) and gestational diabetes (GDH) were eva I uated for each pregnancy. 762 I ow-ri sk s i ngl eton pregnane; es served as a control popul at; on. RESULTS: SGA AGA LGA Controls(n=762) 4.2% 80:"8% ls.O% Twins(n=380) 23.4%* 74.2% 2.4%* *p<O.OOOOOI

AGA/AGA(63%) AGA/SGA(27%) SGA/SGA(10%) l'. MAP 94.1 92.1 91.1 NS HCT 34.9 36.0 34.8 NS PPW(lb) 148.5 141.5 134.5 NS WGP(lb) 42.8 44.5 35.7 NS GA(wks) 36.4 36.5 37.7 NS PW(gm) 1012 868 886 <0.05 The incidence of p, GDM, monochorionicity, and gender did not di ffer among the three groups. The AGA twi n of the AGA/SGA pair had a birthweight significantly smaller than the AGA twin of the AGA/AGA pair. CONCLUSIONS: 1. The odds ratios for predicting SGA and LGA in twi n gestat ions were 6.1 and 0.02, respect i ve I y. 2. PI acenta I weight was the only factor significantly associated with SGA in tw; n gestat i cns.

516 THE DELIVERY TIME INTERVAL OF TWINS AND THE INCIDENCE OF FETAL DISTRESS IN THE SECOND TWIN Steven J Thomas M P x, Kirk A. Keegan, Jr., M.D., Mark A. Morgan, M.D., University of Calnornia, Irvine OBJECTIVES: The purpose of this case control study is to evaluate the relationship of the elapsed time between delivery of first and second twins and the development of fetal distress in the second twin. STUDY DESIGN: Maternal records of 159 consecutive twin gestations delivered at U.C. Irvine Medical Center from July, 1986 to January, 1990 were reviewed. Exclusion criteria included twins less than 26 weeks gestation, birth weight less than 500 grams, cesarean delivery of both twins, fetal demise of one twin, or the presence of congenital anomalies. The remaining 94 sets of twins comprising the study population underwent a trial of labor with vaginal delivery of the first twin. Delivery time between first and second twins, mode of delivery, and frequency of fetal distress were determined. The frequencies, odds ratios with confidence intervals, and chi-square with the Yates correction factor were used for statistical analysis. RESULTS: The second twin was delivered by total breech extraction (n.25, 27%), vacuum-assisted delivery (n.21, 22%), external version (n-2, 2%), spontaneous vaginal delivery (n-28, 30%), and cesarean section (n.18, 19%). The mean interdelivery time was 18 ± 2.9 minutes (R.1-176) and a median of 10 minutes. Sixty-five sets (69%) had an interdelivery interval within 15 minutes, and 29 sets (31%) had > 15 minutes elapse between the first and second twin delivery. Twins with an interdelivery interval of > 15 minutes had a higher frequency of fetal distress of twin B (32% vs 12%, odds ratio 3.21, 0.96<OR<10.79, p •. 05), and a higher frequency of combined vaginal­cesarean delivery (31% vs 14%, odds ratio 2.80, 0.86<OR<9.3, p=.09). CONCLUSION: A delivery time of greater than 15 minutes between first and second twins appears to increase the risk of fetal distress and the need for cesarean delivery of the second twin.

January 1993 Am J Obstet Gynecol

517 TWINS: EFFECT OF DELIVERY METHOD ON NEONATAL OUTCOME WHEN ONE OR BOTH FETUSES IS NONCEPHALIC. L. DiGiovanni, T. Shipp~ C. Rudman~ Dept. OB/Gyn, University of Chicago, Chicago, IL OBJECTIVE: Test hypothesis that outcome is not improved by cesarean delivery when one or both twins is noncephalic. STUDY DESIGN: We evaluated outcome data as related to presentation for all twins delivered from 1982-1992. Included were 501 liveborn pairs > 500 gm with twin A cephalic or breech. We analyzed 5 minute Apgar, arterial and venous cord pH, intraventricular hemorrhage and neonatal death. RESULTS: Of 196 pairs {39.1 %} in cephalic-cephalic presentation, 164.5 {83.9%} delivered vaginally. Of 199 cephalic-noncephalic pairs {39.7%}, 151.5 {76.1%} delivered vaginally. Of 106 pairs {21.2%} with twin A breech, 21 pairs {20%} delivered vaginally. For cephalic-noncephalic twins, there was no significant difference in morbidity comparing abdominal to vaginal delivery. For twins with twin A breech, outcome was not improved by abdominal delivery. For twins < 1500 gm, no improvement in survival rates was found for cesarean section compared to vaginal delivery. 22.9% of infants < 1500 gm in cephalic-noncephalic presentations delivered abdominally died compared to 5.6% delivered vaginally {p < 0.05}. With twin A breech and < 1500 gm: 12% delivered by cesarean section died compared to 11 % delivered vaginally. CONCLUSION: These results suggest that neonatal outcome of twins in whom one or both fetuses is noncephalic, even < 1500 gm, may not be improved by cesarean delivery.

518 PREDICTABILITY OF BRACHIAL BLOOD PRESSURE CHANGES FOR FETAL HEART RATE DECELERATIONS FOLLOWING EPIDURAL ANESTHESIA. P. Mills~ R. Moreno~ G. Loy~ Dept Ob/Gyn, U. of Chicago, Chicago, IL OBJECTIVE: We determined the receiver operating characteristics of brachial mean arterial blood pressure {MAP} drop as a predictive test for fetal heart rate deceleration {FHR DECEL} after epidural. The hypothesiS was that FHR DECEL occur more frequently when MAP drops, and that the magnitude of the drop is greater in patients with FHR DECEL. STUDY DESIGN: FHR DECEL {< 90 BPM for> 2 min} and maximal MAP drop from baseline was retrospectively determined in 80 consecutive patients in the hour after epidural in labor. ROC curve MAP range was 0 to -20 mmHG. RESULTS: The prevalence of FHR DECEL was 19%. The mean drop in MAP in the group without decelerations was 5.5 mmHG {SD 9.7} and in the deceleration group 18.6 mmHg {SO 9.8} {P < 0.005, T-TEST}. The frequency of FHR DECEL in patients experiencing any MAP drop was 28% and in those without any drop, 0% {P < 0.05 X2}, Using a MAP drop of 10 mmHg {chosen by ROC curve} as a predictive test for FHR DECEL, the sensitivity was 75, specificity 72, {+} predictability 40, and {-} predictability 92%. CONCLUSIONS: Given these false-positive and false­negative test rates despite optimization by the ROC curve, better predictive tests should be sought, and other etiologies of FHR DECEL considered.