Weight Gain During Pregnancy Following Bariatric Surgery: Exploring the Influence of Weight Stability and Surgery-to-Conception Interval.

: Weight loss following bariatric surgery can improve fertility. Current guidelines recommend delaying pregnancy for at least 12 months post-surgery for weight stabilization and to support healthy gestational weight gain (GWG). However, evidence supporting this recommendation is limited. This study investigated the impact of preconception weight stability and the surgery-to-conception interval on GWG and examined risk factors for GWG above or below recommendations. : Women aged 18-45 years with singleton pregnancies post-bariatric surgery were recruited before 23 weeks' gestation and followed until delivery. Participants self-reported their weight for the 6 months preceding conception and again at 36 weeks' gestation via an online survey. Weight change (as a percentage of pre-pregnancy weight) was analyzed using stepwise linear and multivariate logistic regression. : Sixty-nine participants completed the study. The percentage of body weight change in the 6 months before conception ranged from -34% to +21%, with significantly greater preconception weight loss observed in those who conceived within 12 months of surgery ( < 0.001). The pre-pregnancy BMI and preconception weight change together explained 24% of the variation in GWG ( < 0.001), while the surgery-to-conception interval was not a significant predictor ( = 0.502). While 70% (34/49) of participants experienced weight gain outside of recommendations, no significant risk factors could be identified. : Weight trajectory prior to conception is a key factor to predict GWG rather than the surgery-conception interval. These findings have important implications for family planning and clinical guidance following bariatric surgery.