550: Effect of obesity on induction across gestational age

Donna R Hallaron, Nicole Marshall, Yvonne W. Cheng, Aaron B. Caughey Saint Louis University, Pediatrics, St. Louis, MO, Oregon Health Science University, Obstetrics and Gynecology, Portland, OR, University of California, San Francisco, Department of Obstetrics, Gynecology, and Reproductive Sciences, San Francisco, CA, Oregon Health and Science University, Department of Obstetrics and Gynecology, Portland, OR OBJECTIVE: To determine the effect of increasing maternal pre-pregnancy body mass index on induction across gestational age. STUDY DESIGN: This is a retrospective cohort study of all liveborn singleton infants born to Missouri residents between 2000 and 2006 using birth certificate data excluding infants 42 weeks. BMI category was based on 2009 Institute of Medicine guidelines. Multivariable regression adjusted for maternal age, race, education, insurance, parity, level of prenatal care, smoking status, and infant gender. RESULTS: Of the 512,482 women in the sample, 0.7% delivered very preterm (24 to 30 weeks), 1.4% preterm (30 to 34 weeks), 6.4% late preterm (34 to 37 weeks), 27.3% early term (37/38 weeks), 56.3% term (39/40 weeks), and 7.9% postterm (41/42 weeks). In the sample, 21.4% were obese, 22.8% were overweight, and 50.5% were normal weight. Induction was directly proportional to gestational age with obese women consistently undergoing induction more often (p 0.001) (Figure). Compared to normal weight women, obese women were more likely to be induced [postterm aOR 1.2 (95% CI 1.2, 1.3) to very preterm aOR 1.6 (95% CI 1.3, 1.9)]. Obese women who were induced were more likely to deliver by cesarean than normal weight women [preterm aOR 1.7 (95% CI 1.2, 2.5), late preterm aOR 1.8 (95% CI 1.5, 2.1), early term aOR 2.7 (95% CI 2.5, 2.9), term aOR 2.4 (95% CI 2.3, 2.5), and postterm aOR 2.2 (95% CI 2.0, 2.5)]. Compared to normal weight women, infants born to obese women who deliver preterm, early term, or term were also more likely to have a low five-minute Apgar score [preterm aOR 1.9 (95% CI 1.0, 3.5), early term aOR 1.6 (95% CI 1.2, 2.0), and term aOR 1.4 (95% CI 1.1, 1.7)]. CONCLUSION: Obese women are more likely to be induced and ultimately deliver by cesarean across gestational age. There is also evidence that infants born to these induced obese mothers are at increased risk for complications. 551 Induction trends for late preterm infants across maternal pre-pregnancy BMI Donna R. Hallaron, Nicole E. Marshall, Yvonne W. Cheng, Aaron B. Caughey Saint Louis University, Pediatrics, St. Louis, MO, Oregon Health and Science University, Obstetrics & Gynecology, Portland, OR, University of California, San Francisco, Department of Obstetrics, Gynecology, and Reproductive Sciences, San Francisco, CA, Oregon Health & Science University, Department of Obstetrics and Gynecology, Portland, OR OBJECTIVE: To identify temporal trends in late preterm induction and determine the effect of increasing maternal pre-pregnancy body mass index (BMI). STUDY DESIGN: This is a retrospective cohort study of all liveborn singleton infants born to Missouri residents between 2000 and 2006 between 24 and 42 weeks gestation using birth certificate data. Late preterm was defined as 34 to 37 weeks gestation versus term (39-40 weeks) . BMI category was based on 2009 Institute of Medicine guidelines. Cochrane-Armitage test of trend was used to assess statistical significance over time. Multivariable regression adjusted for age, race, education, insurance, parity, level of prenatal care, smoking status, and gender. RESULTS: 32,931 infants were born late preterm (baseline 64.3 per 1000). The rate of late preterm induction peaked in 2001 at 20.8% and declined to 17.9% by 2006 (p 0.001). Rates of induction varied by pre-pregnancy BMI (27.7% of obese, 20.5% of overweight, and 16.9% of normal weight women) (p 0.001). These trends varied over time with the largest decrease noted in obese women (Figure). Obese women were 1.64 (95% CI 1.52, 1.76) times more likely to undergo a late preterm induction than normal weight women while overweight women were 1.29 (95% CI 1.19, 1.38) times more likely to undergo a late preterm induction. When stratified by pre-gestational and gestational diabetes then chronic or pregnancy-induced hypertension, the increased risk of late preterm induction for obese and overweight women was only present in non-diabetics and non-hypertensives. Overall, the obese women who underwent late preterm induction were more likely to have a cesarean delivery (aOR 1.87, 95% CI 1.6, 2.18) than normal weight women. However, when stratified, obese diabetics were not at increased risk of cesarean delivery compared to normal weight diabetics. CONCLUSION: The rate of induction has declined over time, particularly in obese women. Those obese women who are induced, however, are more likely to be delivered by cesarean section specifically nondiabetic women, hypertensive women, and non-hypertensive women. PosterSessionIV Epidemiology, Infectious Disease, Intrapartum Fetal Assessment, Operative Obstetrics, Obstetric Quality & Safety, Public Health-Global Health www.AJOG.org