Obesity is linked to many antagonistic health outcomes, including in pregnancy. Nevertheless, there may be little information on the effect of maternal obesity on neonatal mortality and illness.

A recent study published within the American Journal of Obstetrics & Gynecology Maternal-Fetal Medicine discusses the association of maternal body mass index (BMI) in pregnancy with neonatal outcomes. More specifically, the researchers were involved in determining whether maternal obesity increased the danger of poor neonatal outcomes, independent of the presence of pre-existing diabetes and chronic hypertension.

Study: Short-term neonatal outcomes of pregnancies complicated by maternal obesity. Image Credit: FotoDuets / Shutterstock.com

Introduction

Maternal obesity is comparatively common in pregnancy, with about one-third of pregnancies in the USA complicated by obesity. Obesity is linked to maternal hypertension, diabetes, and pre-eclampsia, because it is a chronic inflammatory state.

While pregnant, obese moms usually tend to suffer miscarriage and stillbirth, with the infants born to those moms at a greater risk of congenital anomalies, macrosomia, shoulder dystocia, neonatal death, and meconium aspiration.

The present study examines how maternal obesity affects neonatal health and mortality. Herein, the scientists used data from a set of singleton deliveries from 24-42 weeks’ gestation in 25 hospitals between 2008-2011.

Maternal BMI was classified into the reference group of normal/chubby. The experimental groups of obese (OB), morbidly obese (MO), and super-morbidly obese (SMO) were categorized based on BMI, with values starting from 30-39.9 kg/m2, 40-49.9 kg/m2, and 50 kg/m2 or more, respectively. Reference BMI values were between 18.5-29.9 kg/m2.

All patients in reference and other groups were matched for baseline characteristics similar to age, race, ethnicity, chronic hypertension, diabetes, and former Cesarean section, together with cigarette use and insurance status.

The scientists assessed neonatal death, hypoxic-ischemic encephalopathy (HIE), respiratory distress syndrome, and other neonatal complications. Preterm delivery, defined as birth before 37 weeks gestation, in addition to maternal pre-eclampsia and eclampsia, were also included.

What did the study show?

The present study included over 52,000 patients and their neonates, 42% of whom were OB, and seven% and 1% were MO and SMO, respectively. Obesity was related to pre-existing diabetes, chronic hypertension, and cigarette use, increasing with BMI, though at a lower rate in comparison with the reference group.

Hispanics were overrepresented within the OB group, whereas Black moms were overrepresented within the MO and SMO groups, which also had the next proportion of ladies with a history of Cesarean section. Pre-eclampsia, eclampsia, and Cesarean section were more incessantly reported as BMI increased.

Preterm births were least likely within the OB group but increased from OB to SMO at lower than 37 weeks and lower than 28 weeks gestation. Birth weights tended to extend with maternal BMI, with baby weights greater than 4 kg more likely in pregnancies in OB, MO, and SMO moms. These babies were also more more likely to have a congenital defect.

The chance of neonatal morbidity increased by one-third in neonates born to MO moms in comparison with those born to women within the reference group. Nevertheless, no such association was observed for babies born to OB or SMO moms. Pre-existing obesity and obesity in early pregnancy might predict an increased risk of more significant neonatal morbidity.

What are the implications?

Serious neonatal illnesses were higher for babies born to MO moms as in comparison with those within the reference group, even after allowing for the confounding effects of maternal diabetes, pre-eclampsia, and preterm delivery.

Nevertheless, neonatal deaths didn’t rise in concordance with maternal BMI. Moreover, composite morbidity amongst neonates didn’t increase with rising BMI, provided the presence of chronic hypertension and pre-existing diabetes was accounted for.  

Babies born to MO and SMO moms were more more likely to weigh greater than 4 kg and have congenital disabilities, corroborating earlier reports. Nevertheless, while preterm delivery has been previously observed to be more common in babies born to obese moms, there may be some controversy concerning the validity of this finding, with the present study reporting fewer preterm births amongst OB moms. Conversely, the danger of preterm births at lower than 37 weeks and lower than 28 weeks increased with increasing BMI.

The explanations underlying the increased short-term neonatal morbidity in babies born to obese moms remain to be identified; nonetheless, normalizing the BMI before conception, along with controlling chronic hypertension and diabetes, may help prevent or mitigate the antagonistic impact of obesity on neonatal outcomes.

Journal reference:

• Dinsmoor, M. J., Ugwu, L. G., Bailit, J. L., et al. (2023). Short term neonatal outcomes of pregnancies complicated by maternal obesity. American Journal of Obstetrics and Gynecology. doi:10.1016/j.ajogmf.2023.100874.