Effect of a physical activity and healthy eating lifestyle intervention in pregnancy on fetal growth trajectories: The DALI randomised controlled trial.

Background: Obesity during pregnancy is related to fetal overgrowth. Effective interventions that can mitigate this risk are needed.

Objectives: This study aimed to investigate the effect of a lifestyle intervention for pregnant women with obesity on fetal growth trajectories.

Methods: In the DALI trial, pregnant women with a body mass index ≥29.0 kg/m² and without gestational diabetes at baseline were randomized to counselling on physical activity (PA), healthy eating (HE) or a combination (PA + HE), or to usual care (UC). Fetal growth trajectories were modelled based on a combination of estimated fetal weight (EFW) from repeated ultrasound scans and weight measured at birth. Differences in fetal growth trajectories between groups were assessed.

Results: Three hundred eighty-four women were included. Those in the PA + HE intervention had slower EFW gain from 32 weeks onwards, with differences (PA + HE vs. UC) at 32, 36 and 40 weeks of -54.1 g (-146.7 to 38.9 g), -84.9 g (-194.0 to 24.7 g), and -99.8 g (-227.1 to 28.1 g), respectively. Effects appeared stronger in males, with a difference at 40 weeks of -185.8 g (-362.5 g to -9.2 g) versus -23.4 g (-190.4 g to 143.5 g) in females.

Conclusions: A lifestyle intervention for pregnant women with obesity resulted in attenuated fetal growth, which only reached significance in male offspring. Future larger trials are needed to confirm these findings and elucidate underlying pathways.