Prevalence of and factors associated with obesity during pregnancy in Ireland 2013-2022: a retrospective observational study from a large tertiary maternity hospital.

INTRODUCTION: This study describes the prevalence of and factors associated with obesity during pregnancy (body mass index (BMI) ≥30.0 kg/m²) among women attending a tertiary maternity hospital in Dublin, Ireland, where 1 in 8 deliveries occur nationally. METHODS: The study involved secondary analysis of electronic health records from The Coombe Hospital from 2013 to 2022. BMI was calculated using objective measurement of maternal height and weight in early pregnancy. Descriptive estimates of obesity prevalence during pregnancy were calculated by year. Linear mixed effects regression was used to examine factors associated with BMI during pregnancy. RESULTS: There were 74 233 pregnancies. Mean BMI was 25.5 kg/m² in 2013 and 26.5 kg/m² in 2022. Obesity prevalence was 16.3% (95% CI 15.5% to 17.1%) in 2013 and 22.3% (95% CI 21.3% to 23.4%) in 2022. Prevalence of BMI ≥40.0 kg/m² was 1.6% (95% CI 1.3% to 1.9%) in 2013 and 2.4% (95% CI 2.0% to 2.8%) in 2022. Prevalence of normal-range BMI (18.5-24.9 kg/m2) was 52.9% (95% CI 51.8% to 54.0%) in 2013 and 45.3% (95% CI 44.1% to 46.5%) in 2022. Obesity prevalence was higher in 2022 than in 2013 across all age groups, with larger differences among those aged 20-24 years. Elevated BMI was associated with maternal age, parity, ethnicity, lower socioeconomic status, unplanned pregnancy, psychological problems and smoking. CONCLUSION: This study provides up-to-date descriptive estimates of obesity in early pregnancy in Ireland, allowing international comparisons. The higher obesity prevalence observed in 2022 than in 2013 across all age groups has important public health implications. Findings will support healthcare planning and inform universal and targeted public health strategies.