For a study, researchers sought to compare the use of health-care medical resources in low-risk nulliparous pregnancies based on BMI (weight in kilograms divided by height in meters squared) categories. It was a secondary analysis of a multicenter randomized controlled study that compared expectant care with induction of labor between 39 0/7 and 4/7 weeks of gestation in low-risk nulliparous pregnant women, defined as those lacking typical obstetric reasons for delivery at 39 weeks. At randomization, body mass index was divided into four categories: less than 25, 25–29, 30–39, and 40 or over. Time spent in the labor and delivery department from admission to delivery was the primary outcome of the study. The length of stay (LOS) after birth, total hospital LOS, and antepartum, intrapartum, and postpartum resource usage were all established a priori as secondary outcomes. About 99% of CIs were computed using multivariable generalized linear modeling and logistic regressions.

The study comprised a total of 6,058 pregnant women, with 640 (10.6%) having BMIs under 25, 2,222 (36.7%) having BMIs between 25 and 29, 2,577 (42.5%) having BMIs of 30–39, and 619 (10.2%) having BMIs of 40 or above. Time spent in the labor and delivery department increased from 15.19.2 hours for people with BMIs under 25 to 23.513.6 hours for people with BMIs of 40 or higher, with every 5-unit increase in BMI associated with an average 9.8% increase in time spent in the labor and delivery department (adjusted estimate per 5-unit increase in BMI 1.10, 99% CI 1.08–1.11). Except for blood tests and urinalysis, increasing BMI was not linked to increased antepartum resource usage. Increased BMI, on the other hand, was linked to more intrapartum resource use, longer overall hospital LOS, and postpartum resource use. For example, a 5-unit increase in BMI was linked to a 26.1% increase in antibiotic administration, a 57.6% increase in intrauterine pressure catheter placement, a 5.1% increase in total inpatient LOS, 31.0% increase in postpartum emergency department visits, and 23.9% increase in postpartum hospital admission. Higher BMI was linked to a longer duration from admission to delivery, a longer total hospital stay, and more frequent use of intrapartum and postpartum services in low-risk nulliparous women.