Association of maternal body mass index with maternal comorbidities and perinatal outcomes: a prospective observational study

Background: Evidence across the maternal body mass index (BMI) spectrum is limited in Central India. We assessed associations between third-trimester maternal BMI and maternal and perinatal outcomes. Methods: This prospective observational study enrolled 369 women in the third trimester at a tertiary centre in Ujjain and followed them through delivery. Enrolment BMI was classified as underweight, normal, overweight, or obese using prespecified categories. Maternal and perinatal outcomes were compared using chi-square or exact tests. Results: Among 369 women, 13.3% were underweight, 48.2% had normal BMI, 25.7% were overweight, and 12.7% were obese. Gestational diabetes mellitus increased from 0.0% in underweight and normal groups to 22.1% in overweight and 51.1% in obese women (p<0.001); hypertensive disorders reached 34.0% in obese women (p=0.003). Moderate and severe anaemia were most frequent in underweight women (40.8% and 10.2%; p<0.001). Caesarean delivery increased from 18.4% in underweight to 68.1% in obese women (p<0.001). Low birth weight occurred in 34.7% of neonates born to underweight women; Apgar score <8 and neonatal intensive care admission were most frequent in obese women (17.0% each; p=0.001). Conclusions: Third-trimester BMI was associated with distinct maternal and perinatal outcome patterns. Higher BMI groups had greater metabolic, hypertensive, operative, and postpartum morbidity, whereas underweight women had more anaemia and low-birth-weight neonates. Antenatal nutritional assessment may help guide targeted maternal and neonatal surveillance.