144: Second-trimester maternal serum free β-hCG is associated with discordant growth in twin gestations

associated with discordant growth in twin gestations Neeraj Desai, Amanda Roman, Burton Rochelson, Nidhi Vohra, David Krantz, Meir Greenberg Hofstra North Shore-LIJ School of Medicine, Division of Maternal-Fetal Medicine, Manhasset, NY, NTD Labs/PerkinElmer, Genetic Screening, Melville, NY OBJECTIVE: To determine whether second-trimester aneuploidy serum analytes are associated with adverse perinatal outcomes in twin gestations. STUDY DESIGN: Retrospective case control study of patients with twin gestations who underwent second trimester aneuploidy screening, and delivered at our institution between 2004-2010. Pregnancies with known aneuploidy, structural anomalies, pregnancy reductions, and terminations were excluded. Maternal serum alpha-feto protein(AFP), free -hCG, unconjugated estriol, and inhibin were expressed as corrected MoM. Means and extreme values (95%ile) for each analyte were generated from this twin population and the relationship between maternal and fetal outcomes were analyzed, using Fisher’sexact test and Mann-Whitney. RESULTS: There were 200 pregnancies available for review. The mean maternal age was 34 years, and 10.5% were monochorionic twins. Free -hCG 95%ile ( 2.87 MoM) was significantly associated with birth weight discordance 20% (OR 7.36; 95% CI 1.97-27.5) and discordance 20% with at least one SGA newborn (OR 11.6; 95% CI 3.044.6), p 0.01. The mean free -hCG MoM was also significantly higher in patients who developed hypertension (1.6 vs. 1.2; p 0.05). However, the extreme values were not significantly associated with this outcome(table 1). AFP, inhibin, and estriol MoM levels were not associated with any adverse obstetrical outcome in this cohort. CONCLUSION: Free -hCG 95%ile in the second trimester when measured as part of the aneuploidy screen for twins is associated with discordant growth with or without an SGA infant. Free -hCG may provide an early basis to initiate more frequent surveillance of fetal growth in twin gestations. 145 Pre-pregnant body mass index, gestational weight gain and the risk of operative delivery Nils-Halvdan Morken, Per Magnus, Rolv Skjaerven Haukeland University Hospital, Dept Obstet Gynecol, Bergen, Norway, Norwegian Institute of Public Health, Division of Epidemiology, Oslo, Norway, University of Bergen, Dept Community Medicine and Primary Health Care, Bergen, Norway OBJECTIVE: To assess the risk of operative vaginal delivery and Caesarean section in low risk pregnancies according to maternal pre-pregnant body mass index (BMI); underweight ( 18.5), overweight (2529.9), obese I, II and III relative the normal weight (BMI: 18.5-24.9) and to assess de independent effect of gestational weight gain. STUDY DESIGN: Data from the Norwegian Mother and Child cohort during 1999 to 2008 was used and record linkage with the Medical Birth Registry of Norway was performed. Preeclampsia, chronic hypertension, diabetes prior to pregnancy, gestational diabetes and placenta previa were excluded. Singleton pregnancies with cephalic presentation and gestational age 37 weeks were included. Relative risk (RR) was estimated using generalised linear models with extensions to the binary family and adjusting for maternal age, parity and maternal smoking. RESULTS: After exclusions, 58 193 pregnancies with complete data were included in the analyses. Overweight and obese women had an increased risk of Caesarean section with the strongest association among obese women category III (BMI 40) (RR: 4.0, 95%CI: 3.34.9). There was a tendency of an even stronger association when the acute caesareans were analysed alone. The risk of vacuum assisted delivery was also increased for overweight (RR: 1.1, 95%CI: 1.01-1.2), obese II (RR: 1.3, 95%CI: 1.03-1.6) and obese III (RR: 1.5, 95%CI: 1.1-2.2). There was no significant associations for forceps assisted delivery. Women with a gestational weight gain of 16 kg had a significantly increased risk of forceps delivery (RR: 1.2, 95%CI: 1.1-1.4), vacuum delivery (RR: 1.1, 95%CI: 1.08-1.2) and caesarean section (RR: 1.3, 95%CI: 1.26-1.4) independent of maternal pre-pregnant BMI category. CONCLUSION: Obese and overweight women from a low-risk Norwegian cohort have a considerably increased risk of operative delivery with vacuum and caesarean section. All women, independent of maternal pre-pregnant BMI, should be advised not to increase their gestational weight gain above 16 kg to reduce the risk of operative intervention during delivery. Poster Session I Clinical Obstetrics, Medical-Surgical-Disease, Neonatology, Physiology-Endocrinology www.AJOG.org