137: Are normally grown twin pregnancies with birth weight discordance at risk for adverse outcomes?

weight discordance at risk for adverse outcomes? Lorie Harper, Matthew Weis, Anthony Odibo, Kimberly Roehl, George Macones, Alison Cahill Washington University in St. Louis, Department of Obstetrics and Gynecology, St. Louis, MO OBJECTIVE: Discordant twin growth may be an independent risk factor for perinatal morbidity and mortality; however, this may be attributed to the actual birth weight (BW) of the smaller twin rather than growth discordance. Therefore, we sought to determine the effect of growth discordance on perinatal outcomes in appropriately grown (BW 10%ile) twin pairs. STUDY DESIGN: A retrospective cohort study of all consecutive women with twin pregnancies undergoing ultrasound between 15-22 weeks gestation at a single tertiary center. Study groups were defined by the presence of 20% growth discordance, calculated as the BW difference between twins divided by the larger birth weight. Pregnancies were excluded if BW of either twin was 10%ile on the Alexander growth standard, twin-twin transfusion syndrome or fetal anomalies were diagnosed, or delivery occurred 24 weeks. Dedicated research nurses recorded outcomes prospectively. Primary outcomes were preterm birth (PTB) 37 weeks and admission to the neonatal intensive care unit (NICU). Secondary outcomes included PTB 34 and 28 weeks. Univariable and stratified analyses were performed to estimate the effect of growth discordance on PTB and NICU admissions; analyses were stratified by chorionicity. RESULTS: Of 2,445 twin pregnancies, 1,145 met inclusion criteria. Of these, 86 pregnancies were complicated by growth discordance. After stratifying by chorionicity, growth discordance was associated with adverse outcomes only in monochorionic twins. Discordant dichorionic twins had similar risks of PTB and NICU admission as concordant twins. Discordant monochorionic twins had a higher risk of PTB 34 (risk ratio (RR) 2.5, 95% confidence interval (CI) 1.7-3.6), PTB 28 (RR 8.8, 95% CI 3.7-20.5), and NICU admission (RR 2.9, 95% CI 2.0-4.3). CONCLUSION: In normally grown dichorionic twins, growth discordance 20% is not associated with PTB or NICU admission. However, normally grown monochorionic twins with growth discordance are at higher risk of PTB and at least one NICU admission, even in the absence of growth restriction or twin-twin transfusion syndrome. 138 Maternal obesity decreases pregnancy prolongation following cerclage placement in women with cervical insufficiency Marijo Aguilera, Ruby Nguyen, Lauren Giacobbe, Katherine Jacobs, Kirk Ramin, Jessica Swartout University of Minnesota, Maternal Fetal Medicine, Minneapolis, MN, University of Minnesota, Epidemiology and Community Health, Minneapolis, MN, Minnesota Perinatal Physicians–Abbott Northwestern Hospital, Maternal Fetal Medicine, Minneapolis, MN OBJECTIVE: Maternal obesity is associated with several adverse pregnancy outcomes. Given the definition of cervical insufficiency to include a weakening or defect in cervical structural integrity, we hypothesized that an increase in maternal body mass index (BMI) would supersede the average carrying capacity of the cervix and decrease the length of pregnancy prolongation following cerclage placement. STUDY DESIGN: A retrospective cohort analysis evaluating all cerclage procedures performed by the MFM service in a single tertiary facility between January 2008 and February 2011 was completed. Both prophylactic, and rescue (ultrasound indicated) cerclages were included in our analysis. There were 336 total cerclages performed, and delivery data was available on 266 of these subjects. Of these, 133 were prophylactic, while 133 were rescue. Maternal BMI at time of cerclage was recorded and patients were stratified according to BMI category: 38% classified as normal weight (BMI 25), 29% as overweight (BMI 2529.9), 20% as class I obese (BMI 30-34.9), and 13% as class II obese (BMI 35). Differences in pregnancy prolongation according to BMI were determined using multivariable linear regression. RESULTS: Length of pregnancy prolongation was inversely proportional to maternal BMI using continuous variable analysis (p 0.03). Using multivariate analysis of BMI by category and after controlling for prior preterm delivery, gestational age at cerclage, prophylactic vs. rescue, number of fetuses, and year performed, a significant doseresponse with increasing BMI category was observed. The mean prolongation for the normal weight group was 130 / 45 days (median 134, range 6-195). As compared to normal weight patients, the mean decrease in pregnancy prolongation (in days) was 11 (p 0.06) for the overweight group, 14 (p 0.04) for the class I obese group, and 17 (p 0.02) for the class II obese group. CONCLUSION: Pregnancy prolongation following cerclage is significantly shortened in obese patients. Improved cervical integrity may be an additional benefit of obtaining an ideal weight prior to pregnancy. www.AJOG.org Clinical Obstetrics, Medical-Surgical-Disease, Neonatology, Physiology-Endocrinology Poster Session I