Preconception Weight Change and Pregnancy Outcomes After Bariatric Surgery

Background/Objectives: Consensus guidelines recommend delaying conception for at least 12 months following bariatric surgery to achieve maternal weight stability; however, the impact this has on perinatal outcomes is poorly understood. The aim of this study was to explore the impact of bariatric surgery-to-conception interval and maternal preconception weight change on birth weight and gestational age at birth. Methods: Women aged 18–45 years with singleton pregnancies after bariatric surgery were recruited to a prospective, observational study before 23 weeks’ gestation. Participants self-reported the surgery-to-conception interval and weight change in the six months before conception. Preconception weight change was calculated as a percentage of difference compared to weight at conception. Linear regression assessed predictors of birth weight and gestational age. Results: Data from 68 participants (mean age 32 ± 4.8 years) were analyzed. The median birth weight was 3368 (514) g with 7% (5/68) SGA infants. Women with SGA infants had greater preconception weight loss (12% vs. 0%, p = 0.029), while surgery-to-conception intervals were similar (p = 0.255). Preconception weight change and gestational age were independent predictors of birth weight (p < 0.001), accounting for 58% of its variance. Surgery-to-conception interval did not predict birth weight (p = 0.986). The median gestational age at birth was 39 (2.1) weeks, with 7% (5/68) preterm births. Neither preconception weight change nor surgery-to-conception interval predicted gestational age at birth. Conclusions: Preconception weight change appears to be more influential than surgery-to-conception interval for birth weight and birth of an SGA infant. This suggests a need for individualized counseling regarding timing of pregnancy after bariatric surgery.