Prepregnancy overweight and vitamin D deficiency in mothers and neonates

Overweight is linked to poor vitamin D status, but this relation has not been studied in pregnant women, who must sustain the vitamin D stores of their infants and themselves. Our objective was to relate prepregnancy overweight to vitamin D status of pregnant mothers and their neonates. In a large cohort study, serum 25‐hydroxyvitamin D (25(OH)D) was measured at 4–21 wks' gestation and pre‐delivery in 200 randomly‐selected white and 200 randomly‐selected black women and in cord blood of their neonates. 90% of women reported prenatal vitamin use. Multivariable linear regression was used to assess the effect of maternal BMI on vitamin D status of mothers and newborns. The unadjusted prevalence of severe vitamin D deficiency (25(OH)D <37.5 nmol/l) increased as prepregnancy BMI category increased: underweight 17%; normal weight 20%; overweight 27%; obese 33% (p<0.01). Vitamin D deficiency in neonates was also more common among overweight (33%) and obese (41%) women than underweight (27%) and normal weight women (28%) (p=0.05). After adjustment for race, season, periconceptional multivitamin use, gestational age, and marital status, each 5‐unit increase in prepregnancy BMI lowered maternal 25(OH)D by 3.2 nmol/l (SE 0.8 p<0.001) and lowered neonatal 25(OH)D by 2.0 nmol/l (SE 1.0 p=0.05). Race did not modify these associations. These data suggest that prepregnancy overweight predisposes mothers and their neonates to poor vitamin D status. Although the mechanisms underlying this relation need to be clarified, high‐dose vitamin D supplementation or screening for vitamin D deficiency may be warranted in overweight gravidas and their neonates.