Exploring risks for women who have a pregnancy after bariatric surgery to inform pregnancy and postnatal care needs

Research question What are key pregnancy-related risks for women experiencing pregnancy after metabolic bariatric surgery (MBS), and how do intersectional inequalities influence them? Background In England, ≥50% of pregnant women live with overweight/obesity. MBS is the most effective treatment for severe/complex obesity, but there is some evidence for increased risks of adverse perinatal outcomes post-MBS. Maternal obesity increases postnatal depression (PND) risk, and as women who have pregnancies post-MBS may still be living with obesity, they may be exposed to combined effects of obesity and MBS on PND risk. High-quality evidence-based clinical guidance for these patients is lacking. Aims and Objectives Aims: Examine associations between MBS pre-pregnancy and risks of PND, gestational diabetes (GDM), gestational hypertension, pre-eclampsia and low birthweight baby. Investigate effects of time between MBS and pregnancy, and MBS procedure on associations. Explore intersectional inequalities in associations. Objectives: 1. Estimate proportion of childbirths where the woman had MBS, by year, age, ethnicity, urban/rural and deprivation. 2. Describe characteristics of women who experience childbirth post-MBS. 3. Calculate: a) hazard ratios for PND, and b) relative risks for GDM, gestational hypertension, pre-eclampsia, and c) low birthweight baby for women post-MBS compared with: a. women with childbirth without MBS, with matched BMI. b. women with childbirth without MBS, with a pre-pregnancy BMI in healthy weight range. We will also compare: women who have a pregnancy <24 months post-MBS with pregnancy ≥24 months post-MBS. different MBS procedures. 4. Explore how intersectional inequalities influence associations. Methods Retrospective observational matched cohort studies using data from the Clinical Practice Datalink Aurum, and linked Hospital Episode Statistics Admitted Patient Care data. Main cohort is women following childbirth (index date) post-MBS with obesity code/BMI≥30kg/m2 pre-surgery. Comparator cohorts will be: women with childbirth and obesity code/BMI≥30kg/m2 pre-pregnancy, no MBS. women with childbirth and BMI pre-pregnancy in healthy weight range, no MBS. We will perform 10:1 matching on key characteristics. We will estimate proportions of childbirths where the woman had MBS, stratified by year, and reported by age, ethnicity, urban/rural and deprivation. Cox regression will be used to estimate hazard ratios comparing associations between PND incidence up to 12-months after childbirth in women post-MBS to comparator cohorts, unadjusted and adjusted for confounders. Modified Poisson regression will be used to estimate relative risks for associations between GDM, gestational hypertension, pre-eclampsia during the pregnancy, and low birthweight baby, for women post-MBS compared to comparator cohorts, unadjusted and adjusted for confounders. We will examine outcomes for pregnancies <24 months post-MBS compared with ≥24 months post-MBS and between MBS procedures and explore the impact of intersectional inequalities (age/ethnicity/deprivation) on outcomes. Timelines for delivery Study will be conducted from 01/01/2026 for 21 months. Anticipated Impact and Dissemination We will produce high-quality evidence on associations between MBS history and important pregnancy-related outcomes. Impacts will include new knowledge to help women considering pregnancy post-MBS, informing care and clinical guidance and a platform for further research. We will share results through academic papers/conferences, clinical briefings, and work with our PPIE group to share findings with the public.