Effect of postbariatric maternal weight loss and surgery to conception interval on perinatal outcomes of nulliparous women.

BACKGROUND: Bariatric surgery is associated with an increased risk of delivering a small neonate. The role of maternal weight loss and surgery to conception interval is unclear. OBJECTIVES: To investigate the effect of maternal weight loss, as a result of bariatric surgery, and surgery to conception interval on fetal growth and birthweight (BW). SETTING: Inner London Teaching Hospital METHODS: We studied prospectively nulliparous women with previous bariatric surgery. Information on type, time, and presurgery weight was obtained. Surgery-to-conception interval was calculated as the time between surgery and conception, defined as the fourteenth day of the pregnancy dated by first trimester ultrasound scan. In the first trimester, maternal weight was measured. Assessment of maternal weight change between presurgery and first trimester of pregnancy was defined as total weight loss (TWL) (%). Fetal ultrasound scans were performed twice; 30-32 and 35-37 weeks' gestation and estimated fetal weight (EFW) was calculated. Fetal growth rate was calculated as the ratio of EFW increase (in grams) between 30-32 and 35-37 weeks divided by the time interval (in days) between the 2 examinations. BW was recorded. RESULTS: The study included 54 pregnant women, 26 with a restrictive procedure (gastric band or vertical sleeve gastrectomy) and 28 with a gastric bypass. Surgery to conception interval was not a significant predictor of the offspring's growth. Maternal TWL was a significant predictor of fetal growth rate (P = .04) and predictor of BW (P = .005), even after adjustment for confounders. CONCLUSIONS: Maternal weight loss, as a result of bariatric surgery, has an inverse correlation with fetal growth rate and BW.