Association Between Early Pregnancy Body Mass Index and Gestational Weight Gain in Relation to Neonatal Birth Weight

Maternal early pregnancy body mass index (BMI) and gestational weight gain (GWG) strongly correlate with pregnancy outcomes. Gestational hypertension and diabetes have been associated with overweight and obesity in pregnancy. A low pre-pregnancy BMI has been associated with low birth weight and preterm birth.

This observational study was carried out from November 2018 to July 2020 in a tertiary care hospital in South India with a sample size of 100. Pregnant women with uncomplicated singleton pregnancies booked for regular antenatal care by 10 weeks of gestation were included in the study. During the participants' antenatal check-ups, detailed history and examinations were made. The weight of the participants was recorded at every antenatal check-up. Information about the gestational age at delivery and the birth weight of the neonates were collected following delivery.

The mean age of women was 25.83 + 2.74 years. Of women who delivered low birth weight neonates (<2.5 kg), 86% had GWG below the Institute of Medicine (IOM) recommendation. A total of 57% of women with normal early pregnancy BMI and 67% of obese women had GWG within the IOM recommendation. Early pregnancy BMI had a positive correlation with neonatal birth weight (r (98) = 0.779, p = 0.001). Of the underweight pregnant women, 72% gave birth to small for gestational age (SGA) babies, and 97% percent of normal early pregnancy BMI women delivered neonates with normal weight for gestational age. A total of 33% of overweight and 50% of obese women had large for gestational age (LGA) babies.

Results from this study suggest that maternal early pregnancy BMI is more strongly associated with neonatal birth weight than GWG. Therefore, early pregnancy BMI may be an important focus for counseling during pregnancy.