Gestational weight gain and estimated fetal growth in different trimesters among Saudi women

Maternal weight gain during pregnancy affects fetal growth. This study aimed to determine the association between gestational weight gain (GWG) and fetal weight gain at different weeks of gestation. The study also intended to determine the relationships among maternal pre-pregnancy body mass index (BMI), GWG, and neonatal birth weight.

This prospective observational cohort study examined 316 pregnant women at Security Forces Hospital, Makkah, from July 1st, 2023, to June 30th, 2024. All uncomplicated, singleton, booked cases with term deliveries were included. Maternal pre-pregnancy weight and BMI were determined and categorized as normal, overweight, or obese. Participants were followed up with from 18 ± 1 weeks until delivery. Gestational weight gain and estimated fetal weight by ultrasound were recorded and compared at weeks 18, 24, 28, 32, and 36.

GWG showed no significant correlation with estimated fetal weight at 18 weeks (B=0.001, p=0.242) and 24 weeks (B=0.003, p=0.242). However, GWG at 28 weeks (B=0.044, p<0.001), 32 weeks (B=0.029, p=0.001), and 36 weeks (B=115.13, p<0.001) strongly predicted fetal weight at the corresponding weeks. Pre-pregnancy weight (r=0.10, p=0.073) and BMI (r=0.08, p=0.164) showed non-significant correlations with neonatal birth weight. However, total GWG (B=0.068, p<0.001) and pregnancy duration (B=20.81, p<0.001) significantly influenced birth weight. Despite variations in GWG, average birth weights were relatively similar across all BMI maternal groups, with the obese group having the highest birth weights, followed by the overweight and normal groups.

Maternal GWG directly affects fetal weight (especially during the third trimester) and birth weight.