Pregravid BMI strongly predicts maternal, infant outcomes

Prepregnancy body mass index (BMI) appears to more strongly influence pregnancy outcomes than maternal age, a recent China study has found.

A total of 51,125 singleton pregnant women participated in the study. Prepregnancy weight was determined through self-reports, while weight during pregnancy was measured with an ultrasonic metre. Outcomes included gestational diabetes mellitus (GDM), pre-eclampsia, caesarean delivery, and infant body weight and length.

Multiple logistic regression models showed that women who were overweight (BMI 23–24.9 kg/m²) or obese (BMI ≥25 kg/m²) before pregnancy were at a significantly higher risk of GDM (odds ratio [OR], 2.16, 95 percent confidence interval [CI], 2.05–2.26), pre-eclampsia (OR, 2.89, 95 percent CI, 2.50–3.35), and caesarean delivery (OR, 1.58, 95 percent CI, 1.51–1.65).

Neonatal outcomes were also adversely affected by prepregnancy overweight or obesity: preterm delivery (OR, 1.38, 95 percent CI, 1.26–1.51), stillbirth (OR, 1.69, 95 percent CI, 1.41–2.02), and macrosomia (OR, 1.92, 95 percent CI, 1.75, 95 percent CI, 1.75–2.11). Small for gestational age was less likely (OR, 0.65, 95 percent CI, 0.56–0.75), while the risk of large for gestational age was exacerbated (OR, 1.80, 95 percent CI, 1.70–1.90).

Notably, the Gradient Boosting Machine analysis showed that pregravid BMI was a more important predictor of the study outcomes than maternal age, except for caesarean and preterm delivery.

“In summary, a mother who is underweight or overweight/obese before a pregnancy could result in higher risk of adverse maternal and neonatal outcomes. To improve pregnancy outcomes, normal BMI weight as well as relatively young maternal ages are recommended before women plan to have children,” the researchers said.