Maternal Obesity Is Associated With Adverse Pregnancy Outcomes in Inflammatory Bowel Disease: A Matched Electronic Health Record Cohort Study

BACKGROUND: We sought to define the prevalence of obesity in the first trimester of pregnancy among women with inflammatory bowel disease (IBD) and evaluate its association with adverse pregnancy outcomes. METHODS: First-trimester body mass index (BMI) was assessed in pregnancies with and without IBD. Pregnancies reaching 24 weeks were propensity-score matched 1:6 by maternal age, BMI, smoking status and gravidity to assess whether IBD conferred additional pregnancy risk. RESULTS: Overall, 22.6% (64/283; 95% CI 17.7%-27.5%) of pregnancies in women with IBD met ethnicity-adjusted criteria for obesity. Increasing obesity class was associated with stepwise increases in gestational diabetes, pre-eclampsia, venous thromboembolism (VTE), emergency caesarean section and high birthweight. Matching yielded 177 IBD pregnancies and 1062 controls. Obesity was independently associated with the composite adverse pregnancy outcome (OR 1.63; 95% CI 1.15-2.33; p = 0.007), whereas no statistically significant additional association was identified for IBD diagnosis alone (OR 0.74; 95% CI 0.53-1.03; p = 0.073). Among IBD pregnancies, aspirin was recommended in 39.3% (86/219). Low-molecular-weight heparin (LMWH) was prescribed in 21.6% (19/88) of pregnancies classified post hoc as intermediate or high VTE risk. CONCLUSION: More than one in five pregnancies in women with IBD were complicated by obesity. Obesity was strongly associated with adverse pregnancy outcomes, whereas this study did not identify a significant additional effect attributable to IBD diagnosis alone. Preventive prescribing with aspirin and LMWH represents an opportunity for improved antenatal care.