Plasma 25-hydroxyvitamin D during pregnancy and small-for-gestational age in black and white infants

PurposeIn a prospective prenatal cohort study, we examined associations of second trimester and cord plasma 25-hydroxyvitamin D (25[OH]D) with small-for-gestational age (SGA) and the extent to which vitamin D might explain black/white differences in SGA.MethodsWe studied 1067 white and 236 black mother-infant pairs recruited from eight obstetrical offices early in pregnancy in Massachusetts. We analyzed 25(OH)D levels using an immunoassay and performed multivariable logistic models to estimate the odds of SGA by category of 25(OH)D level.ResultsMean (SD) second trimester 25(OH)D level was 60 nmol/L (SD, 21) and was lower for black (46 nmol/L [SD, 22]) than white (62 nmol/L [SD, 20]) women. Fifty-nine infants were SGA (4.5%), and more black than white infants were SGA (8.5% vs. 3.7%). The odds of SGA were higher with maternal 25(OH)D levels less than 25 versus 25 nmol/L or greater (adjusted odds ratio, 3.17; 95% confidence interval, 1.16–8.63). The increased odds of SGA among black versus white participants decreased from an odds ratio of 2.04(1.04, 4.04) to 1.68(0.82, 3.46) after adjusting for 25(OH)D.ConclusionsSecond trimester 25(OH)D levels less than 25 nmol/L were associated with higher odds of SGA. Our data raise the possibility that vitamin D status may contribute to racial disparities in SGA.