437 Overweight and Irregular Menstrual Cycle Before Pregnancy and Preterm Birth

Abstract

Background and aims: Obesity and pre-pregnancy irregular menstrual cycle may independently increase the risk of preterm birth. High body mass index (BMI) and irregular menstrual cycle are both symptoms of the polycystic ovary syndrome (PCOS). The endocrine profile in women with PCOS may further increase the risk of preterm birth. The aim of this study is to investigate the interaction between BMI and irregular menstrual cycle on the risk of preterm birth.Methods: A population of 55,889 women enrolled in the Aarhus birth cohort was studied. The women were followed during pregnancy and delivery. Self reported data on height and pre-pregnancy weight was used to define 4 groups of BMI: 0-18.5, 18.5- 25, 25-30 and >30 kg/m2. Groups of self-reported irregular menstrual cycle (yes/no) were used. Odds ratios (OR) of preterm birth, i.e. before 37 completed gestational weeks, determined by ultrasonography, were estimated using logistic regression models.Results: Compared to normal weight women (BMI 18.5-25) with regular menstrual cycle, the OR's of preterm birth for women with other BMI and cycle characteristics were: Regular cycle; BMI 0-18.5, 1.34 (95 % confidence interval (CI): 1.12; 1.60); BMI 25-30, 1.31 (1.16; 1.48); BMI >30, 1.44 (1.20; 1.73). Irregular cycle: BMI 0-18.5, 1.62 (95 % CI: 1.31; 1.99); BMI 18.5-25 1.12 (1.03; 1.23) BMI 25- 30, 1.24 (1.06; 1.45); BMI >30, 1.70 (1.37; 2.10).Conclusion: Obese women with a pre-pregnancy irregular menstrual cycle had an increased risk of preterm birth. The prevalence of polycystic ovary syndrome is expected to be higher among these women.