Maternal morbidity and mortality rates in the United States (US) exceed those of other high-income countries [1,2]. One of the factors contributing to severe maternal morbidity is the prevalence of cesarean deliveries [[3], [4], [5]]. In the US, the percentage of women undergoing cesarean deliveries has risen significantly, from 7% in 1990 to 32% in 2023, surpassing the World Health Organization’s acceptable range of 10-15% [[6], [7], [8]].

Although cesarean delivery can decrease maternal and neonatal morbidity and mortality when medically necessary, unnecessary cesarean delivery increases the risk of short- and long-term adverse outcomes for both the mother and infant [4]. Cesarean deliveries are associated with risks of maternal complications, including hemorrhage requiring transfusion, infections, septic shock, uterine rupture, placenta previa, hysterectomy, and complications in future pregnancies [5]. Epidemiological studies have shown that a cesarean delivery is associated with a higher incidence of noncommunicable diseases in infants, including asthma, food allergies, and obesity [5]. These findings may be partially explained by a lack of exposure to diverse microorganisms encountered during vaginal birth, which contribute to development of the immune system [9]. Reducing cesarean deliveries is a priority outlined by the Centers for Disease Control and Prevention Healthy People 2030, the American College of Obstetricians and Gynecologists, and the Alliance for Innovation on Maternal Health [10,11].

One of the noted risk factors for cesarean delivery is excessive gestational weight gain (EGWG). The Institute of Medicine (IOM) and World Health Organization provide specific guidelines for appropriate gestational weight gain (GWG) based on pre-pregnancy body mass index (BMI) in an effort to reduce risks associated with weight gain below or exceeding recommend rates during pregnancy and promote healthy outcomes for mothers and infants [12,13]. With the growing number of women experiencing pre-pregnancy obesity and EGWG [14,15], exploring the relationship between pre-pregnancy obesity and EGWG may provide insights for reducing the high rates of cesarean deliveries in the US. Although several studies have identified an association between EGWG and cesarean delivery, most of the investigations involved small sample sizes and were conducted among a single racial or ethnic group [[16], [17], [18]]. Previous research has not explored whether the relationship between EGWG and cesarean delivery risk varies across BMI categories. Numerous clinical and nonclinical factors associated with cesarean deliveries are difficult to modify; pre-pregnancy BMI and pre-pregnancy health conditions, as well as factors such as maternal age, race, socioeconomic status, and insurance coverage, are rooted in individual circumstances and/or systemic issues that can be challenging to change through discrete interventions [14,[19], [20], [21]]. However, GWG is a potentially modifiable factor. This research investigated associations between EGWG and increased risk of cesarean delivery among low risk (nulliparous, singleton term births with cephalic presentation) for women across a range of BMI categories.