When to conceive following metabolic-bariatric surgery to optimize both surgical weight loss and gestational weight gain

Most patients undergoing metabolic-bariatric surgery are women and half of them are at reproductive age. Although it is recommended delaying pregnancy after surgery, the optimal time to conceive yet remains controversial. This study aimed to define the best conception time following surgery to optimize both surgical weight loss and gestational weight gain. This cohort study included all women who gave birth after surgery recorded in the Iranian National Obesity Surgery Database during 2009–2023. First, weight loss pattern from surgery to pregnancy was addressed by curve fitting and univariate segmented relationship and then evaluated by regression model added with maternal and perinatal outcomes. Overall, 430 women with a mean age of 33.81 ± 4.70 years, entered the analysis. We revealed two change points of 4 and 13 months in weight loss trend from surgery to pregnancy. Accordingly, pregnancy within 4–13 and over 13 months was significantly associated with a higher mean of percent total weight loss (β = 13.35, 95%CI: 9.24, 17.46 and β = 14.32, 95%CI: 10.24, 18.40, respectively) and a lower risk of inadequate gestational weight gain (OR = 0.26, 95%CI: 0.09, 0.75 and OR = 0.12, CI: 0.04, 0.34, respectively) than pregnancy before 4 months following surgery. Pregnancy at least 13 months after metabolic-bariatric surgery is associated with greater surgical weight loss and a lower risk of inadequate gestational weight gain. Therefore, we recommend a broad guide of 12–18 months as the earliest time to plan for pregnancy after surgery.