Abstract Background We sought to define the burden of obesity in the first trimester in pregnant women with IBD and its influence on adverse pregnancy outcomes. Methods We extracted ICD-10 coded data on pregnancies in women with and without IBD between 1/9/20 and 13/11/25. Body mass index (BMI) was assessed in the first trimester. Adverse pregnancy outcomes were gestational diabetes, pre-eclampsia, emergency Caesarean section, still birth (after 24 weeks of pregnancy), prematurity (delivery before 37 weeks’ gestation), high or low birth weight (4000g and 2500g), and venous thromboembolism (VTE). To determine if IBD is an additive risk factor for an adverse pregnancy outcome, we matched each pregnancy at week 24 in women with IBD to 6 in women without IBD, according to age at conception, BMI and number of prior births. Results There were 68.3% (168/246) and 62.4% (17364/27845) births in women with and without IBD, respectively. Of these 0% and 0.4% were still births. The median BMI in women with and without IBD was not different. Older age (OR 0.99 95% CIs 0.98-0.99 p 0.001); non-white ethnicity (OR 0.56 95% CIs 0.49-0.64 p 0.001) and lower social deprivation (OR 0.99 95% CIs 0.99-0.99 p 0.001) were associated with a lower risk of obesity; whereas urban living (OR 1.10 95% CIs 1.03-1.17 p = 0.008) was associated with a higher risk of obesity. A dose-dependent risk of gestational diabetes, pre-eclampsia, prematurity, emergency Caesarean section, high birth weight and VTE (Table 1) was associated with increasing class of obesity. 21.2% (53/250 95% CIs 16.4-26.9%) of pregnant women living with IBD were obese. In our matched cohort, there was no difference in the risk of an any adverse pregnancy outcome in women living with and without IBD, irrespective of disease activity (OR 0.69 95% CIs 0.47-1.01 p = 0.06). There was no additional risk in women living with both IBD and obesity compared to those living with obesity without IBD (OR 1.17 95% CIs 0.49-2.72 p = 0.7). 35.5% (86/242) were deemed to be at risk of VTE, but only 9.5% (23/242) were prescribed low molecular weight heparin (LMWH). Based on 2025 international consensus1 statement all women with IBD should be treated with aspirin, to mitigate the risk of preeclampsia, but only 33.2% (65/196) were. Conclusion Counter-intuitively, one in five pregnant women with IBD were living with obesity in the first trimester. Obesity was associated with a dose-dependent increase in adverse pregnancy outcomes: a diagnosis of IBD per se was not an additive risk factor. Two thirds of patients at risk of pre-eclampsia and VTE were not treated with aspirin or LMWH. Reference: 1) Mahadevan U, Seow CH, Barnes EL, et al. Global consensus statement on the management of pregnancy in inflammatory bowel disease. Gut Published Online First: 28 August 2025. doi: 10.1136/gutjnl-2025-336402 Conflict of interest: Dr. Roberts, Christopher: Funding of research: Nova Ltd, Open Targets Smith, Rebecca: Nil Safwat, Odeh: Nil Cairnes, Vida: Nil Bewshea, Claire: Nil Kennedy, Nicholas Alexander: Grant: Dr Kennedy’s department has received research funding from AbbVie, Biogen, Celgene, Celtrion, Galapagos, MSD, Napp, Pfizer, Pharmacosmos, Roche and Takeda Personal Fees: Dr Kennedy has served as a speaker and/or advisory board member for AbbVie, Amgen, BMS, Falk, Ferring, Galapagos, Janssen, Mylan, Pharmacosmos, Sandoz, Takeda and Tillotts Non-financial Support: Dr Kennedy has had support to attend meetings from AbbVie, Falk, Janssen and Tillotts Jennifer, Blackman: Nil Bell, Sally: Nil Ahmad, Tariq: Tariq Ahmad reports grants, personal fees and non-financial support from F. Hoffmann-La Roche AG, Biogen Inc, Abbvie, Janssen, Celltrion Healthcare, Galapagos NV, Immundiagnostik, Takeda, ARENA, Gilead, Adcock Ingram Healthcare, Pfizer, Genentech, Tillotts. Goodhand, James Ross: No conflict of interest Clough, Jennie: Personal Fees: I received sponsorship for my ECCO attendance fee from Galapagos.
Roberts et al. (Thu,) studied this question.