Effect of pregravid obesity on perinatal outcomes in singleton pregnancies following in vitro fertilization and the weight-loss goals to reduce the risks of poor pregnancy outcomes: A retrospective cohort study

OBJECTIVE: In the present study, we aimed to determine whether pregravid obesity independently predicts increased risks of perinatal complications following in vitro fertilization (IVF) and the weight loss goals to reduce the risk of poor pregnancy outcomes. DESIGN: Retrospective cohort study. POPULATION: All pregnancies after first the fresh IVF cycle from January 2014 to December 2016 in the Reproductive Center affiliated to Shandong University were reviewed. A total of 3,962 eligible singleton births were stratified into cohorts based on the body mass index (BMI) definitions of the Working Group on Obesity in China (WGOC). MAIN OUTCOME MEASURES: Adverse perinatal outcomes. RESULTS: Pregravid overweight and obesity were associated with increased risks of gestational diabetes mellitus (GDM), hypertensive disorders of pregnancy (HDP), including gestational hypertension (GH) and pre-eclampsia (PE), polyhydramnios, preterm premature rupture of the membranes (PPROM), placental abruption, preterm birth (PTB) <37 weeks, caesarean section (CS), fetal macrosomia, large for gestational age (LGA) >90th percentile, neonatal respiratory distress syndrome (NRDS), neonatal intensive care unit (NICU) admission and congenital anomalies as compared with the normal-weight group after adjustment of differences in age, parity, polycystic ovary syndrome (PCOS) and type of controlled ovarian hyperstimulation (COH). The increased risks of PPROM, NRDS and congenital anomalies were eliminated after adjustment of GDM development, whereas the increased risk of NRDS disappeared after adjustment of HDP. Placenta previa was not significantly different between the obese group and reference group (REF). Moreover, the rates of postpartum hemorrhage (PPH), PTB<32 weeks, small for gestational age (SGA) >90th percentile and perinatal mortality were also not significantly different between above-mentioned two groups. For obese women, a 10%-15% reduction in prepregnancy BMI was associated with significantly decreased risks of GH, CS and fetal macrosomia. For overweight women, just a 5% reduction in BMI could significantly reduce the risks of GDM, CS and fetal macrosomia. CONCLUSIONS: Pregravid obesity could independently predict a higher risk of adverse pregnancy outcomes after adjustment of differences in maternal age, parity, PCOS, and type of COH in IVF pregnancies. The potential mechanism that obesity potentiated the risks of some poor perinantal outcomes might occur through the development of GDM and HDP. A 10%-15% reduction in pregravid BMI for obese women and a 5% reduction for overweight women were associated with a significant reduction of poor perinatal complications.