Background: Obesity in pregnancy is known to increase the maternal, neonatal and childhood risks of adverse outcomes. We aimed to determine the influence of obesity class on maternal and perinatal outcomes and to explore the contribution of other maternal factors including age, country of origin, parity, presence of pre-existing and current diabetes disorders and hypertension on outcomes such as large-for gestational age (LGA), small for gestational age (SGA) and neonatal hypoglycaemia.
Methods: We retrospectively analysed data from all singleton births from obese mothers from 2013 – 2017 in Northern Sydney Local Health District in Sydney, NSW, Australia. Maternal obesity was categorized into obesity class I (BMI 30-34.9), class II (BMI 35-39.9) and class III and above (BMI 40+). The primary outcomes were LGA and SGA neonatal size. The secondary outcomes were neonatal hypoglycemia, birth defect and timing of birth. Univariate and multivariate logistic analysis model were used to explore the impact of maternal cofounders on neonatal outcomes.
Results: Of 2466 births to obese women, neonatal LGA was more likely in women with obesity class III and above vs class I (OR=1.47, 95% CI 1.03-2.08, p=0.04), multiparous vs nulliparous (OR=1.52 – 1.78, 95% CI 1.19-2.62, p=0.01), and age over 40 vs age under 25 years old (OR=1.86, 95% CI 2.16-2.99, p=0.01). In the obesity class III and above group, women with pre-existing gestational diabetes had more than one-and-half times higher risk of LGA than women without pre-existing GDM (OR=1.66, 95% CI 1.09-2.54, p=0.03). Birth defects were increased more than two-fold for women with obesity class III and above compared with class I (OR=2.17, 95% CI 1.01-4.66, p=0.045).
Conclusion: Increasing maternal obesity class increases risk of adverse perinatal outcomes including delivering an LGA neonate and birth defects, independent of maternal comorbidities such as diabetes and age.