SUN-536 Gestational Weight Gain and Pregnancy Outcomes in Women with a History of Bariatric Surgery at Imperial College Healthcare NHS Trust, London, UK

Abstract Disclosure: S. Ansari: None. M. Xia: None. R. Valaiyapathi: None. K. Alexiadou: None. R. Houghton: None. C. Bovill-Taylor: None. K. O’Donnell: None. C. Price: None. C. Tsironis: None. S. Pukayastha: None. A. Ahmed: None. R. Agha-Jaffar: None. B. Jones: None. C. Yu: None. A. Dornhorst: None. E. Mullins: None. B.C. Khoo: None. T. Tan: None. Background: Pregnancies following bariatric surgery have been associated with adverse perinatal outcomes (e.g. preterm delivery, low birth weight), potentially due to insufficient gestational weight gain. This may be particularly relevant for women conceiving within 12 months post-surgery before achieving weight stability.Objective: To compare pregnancy outcomes between women who conceived within 12 months after bariatric surgery and those who conceived later at Imperial College Healthcare NHS Trust (ICHNT), London, UK. Methods: In a prospective study of 109 pregnancies after either sleeve gastrectomy (SG, n=64) or Roux-en-Y gastric bypass (RYGB, n=45), 85 women have delivered (SG=51; RYGB=34). Participants were categorised by surgery-to-conception interval (SCI) into two groups: <12 months (n=20) and ≥12 months (n=65). Primary outcomes were gestational weight gain and birth weight. Secondary outcomes included the effect of pre-pregnancy BMI (≥30 vs. <30), incidence of gestational diabetes (GDM), micronutrient levels, and glycaemic variation measured by 10-day blinded DEXCOM G6 continuous glucose monitoring. Results: Women with SCI <12 months gained significantly less weight during pregnancy compared with those with SCI ≥12 months (3.49 ± 8.95 vs. 8.20 ± 4.63 kg, p=0.01), despite similar pre-pregnancy BMIs (30.07 vs. 29.70 kg/m², p=0.49). Neonatal birth weight (2968.8 ± 507.8 vs. 3038.9 ± 526.6 g, p=0.60) and gestational age at delivery (270 ± 13 vs. 269 ± 10 days, p=0.71) were comparable between groups, and GDM incidence was similar (25.0% vs. 24.6%). Maternal micronutrient levels, dietetic input, and glycaemic variation did not differ significantly. Irrespective of SCI, women with pre-pregnancy BMI ≥30 gained slightly less weight than those with BMI <30 (5.98 ± 6.59 vs. 8.28 ± 5.30 kg, p=0.09). Notably, within the SCI <12 group, those with BMI ≥30 gained significantly less weight than their BMI <30 counterparts (−1.72 ± 8.71 vs. 7.96 ± 6.81 kg, p=0.0461); no BMI-related differences were found in the SCI ≥12 group. Discussion: Although women conceiving within 12 months gained less weight during pregnancy, neonatal birth weight and other major outcomes were similar between the groups. This finding contrasts with earlier reports suggesting increased risk in early post-surgery pregnancies, and may reflect the benefits of intensive obstetric and dietetic care (including frequent reviews, routine monitoring, and tailored micronutrient supplementation) at our centre. The small sample size in the SCI <12 month group (n=20) may limit the power to detect more subtle differences and affects generalisability. Conclusion: With active, specialist care, women conceiving within 12 months of bariatric surgery demonstrated comparable pregnancy outcomes to those who conceived later, despite significantly lower gestational weight gain. Presentation: Sunday, July 13, 2025