Maternal Pregestational Body Mass Index and Delivery Outcomes: A Retrospective Study in a Tertiary High-Income Setting.

BACKGROUND

Maternal overweight (OW) and obesity are increasingly prevalent worldwide and have been linked to adverse pregnancy and delivery outcomes. This study aims to evaluate maternal and neonatal outcomes in pregnancies stratified according to pregestational body mass index (BMI) in a tertiary care setting in Italy.

METHODS

This retrospective study included all singleton live births between 2022 and 2024 at the IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy. Women were classified into four groups based on pregestational BMI: (1) underweight (UW, BMI < 18.5 kg/m2, n = 1796); (2) normal weight (NW, BMI 18.5-24.9 kg/m2, n = 11,710); (3) OW (BMI ≥ 25.0 kg/m2, n = 2313); and (4) obese (OB, BMI ≥ 30.0 kg/m2, n = 976). Delivery outcomes were compared among groups using binary logistic regression and generalized linear models adjusted for confounding factors.

RESULTS

Inclusion criteria were met by a population of 17,813 singleton pregnancies. Multivariate models confirmed that OB women were independently associated with virtually all adverse delivery outcomes, including higher odds of preterm birth (aOR 1.48), labor induction (aOR 1.69), emergency cesarean delivery (aOR 1.42), postpartum hemorrhage (aOR 1.40), APGAR score at 5 min lower than 6 (aOR 2.77), and admission to neonatal intensive care unit (aOR 2.05) compared to NW controls. OW women were at higher risk of emergency cesarean delivery and postpartum hemorrhage, while UW women showed largely comparable outcomes to NW women, with the sole exception of reduced birthweights and higher odds of episiotomy use.

CONCLUSIONS

Maternal OW and OB are associated with increased maternal and neonatal morbidity, highlighting the complex obstetric challenges in this population. These findings underscore the need for a BMI-tailored obstetric care and preventive public health strategies targeting women of reproductive age.