Abstract
Background: The achievement of target 25-hydroxyvitamin D [25(OH)D] concentrations in pregnancy may be altered by maternal obesity.
Objective: The authors examined the effects of maternal supplementation of 10 mu g compared with 20 mu s vitamin D-3/d on maternal and umbilical cord 25(OH)D. The secondary aim was to investigate the influence of maternal BMI (in kg/m(2)) on the response of the primary outcomes.
Methods: The authors performed a 2-arm parallel double-blind randomized trial with 240 pregnant women recruited throughout the year in Northern Ireland. Women were stratified by BMI to receive 10 or 20 mu g vitamin D-3/d from 12 gestational wk (GW) until delivery. Maternal blood samples collected at 12, 28, and 36 GW and from the umbilical cord were analyzed for total serum 25(OH)D. A total of 166 women completed the study.
Results: Mean +/- SD 25(OH)D at 36 GW was 80.8 +/- 28.2 compared with 94.4 +/- 33.2 mnol/L . (P < 0.001) (10 compared with 20 mu g vitamin D-3/d, respectively). In those classified with 25(OH)D <50 nmol/L at baseline and assigned 10 mu g vitamin D-3/d. mean 25(OH)D concentrations remained <50 nmol/L at 36 GW, whereas those <50 nmol/L at base-line and assigned 20 mu g vitamin D-3/d, had mean 25(OH)D concentrations >50 nmol/L at 28 and 36 GW. In women with obesity and 25(OH)D <50 nmol/L at baseline, the related mean umbilical cord 25(OH)D was deficient (<25 nmol/L) in both treatment groups. whereas those with obesity and 25(OH)D >= 50 nmol/L at baseline had an average umbilical cord 25(OH)D between 25 and 50 nmol/L in both treatment groups.
Conclusions: Supplementation of 20 mu g vitamin D-3/d is needed to attain maternal and umbilical cord 25(OH)D concentrations >= 50 nmol/L on average, in those who start pregnancy with low 2.5(OH)I) concentrations ( <50 nmol/L). Under current recommendations, women with obesity and low 25(OH)D in early pregnancy are particularly vulnerable to maintaining a low 25(OH)D concentration throughout pregnancy and having an infant born with deficient 25(OH)D concentrations.