Impact of gestational weight gain on fetal growth in obese normoglycemic mothers: a comparative study.

Objective: To assess the pattern of gestational weight gain (GWG) and its effect on fetal growth among normogylycemic obese and lean mothers.

Design: Prospective longitudinal study.

Setting: Teaching hospitals, Sheffield, UK.

Population: Forty-six euglycemic obese and 30 lean mothers and their offspring.

Method: The contrast slope of GWG was calculated and its impact on fetal growth trajectory and birth anthropometry examined in both groups.

Results: The GWG contrast slope trended significantly upward in both groups but it was steeper among lean mothers (p = 0.003), particularly in second trimester. Lean mothers had a biphasic GWG pattern with a higher early weight gain (p = 0.02), whereas obese mothers had a monophasic GWG. Both groups had similar third trimester GWG. The GWG contrast slope was influenced by early pregnancy maternal anthropometry in the obese group only. Nonetheless, the obese mothers' glucose and insulin indices had no significant relationship to GWG. GWG had a significant positive relationship with intrauterine femur length (r = 0.32, p = 0.04) and abdominal circumference (r = 0.42, p = 0.006) growth trajectories, as well as birthweight standard deviation scores (r = 0.32, p = 0.036) and the ponderal index (r = 0.45, p = 0.003) in the obese mothers.

Conclusions: Gestational weight gain among lean mothers is biphasic and significantly higher than their obese counterparts, but without effect on fetal growth. The obese mothers' monophasic weight gain was influenced by their anthropometry, but not by their insulin or glucose indices, and impacted on the growth of their babies.