CONTEXT: Vitamin D regulates 3% of the human genome, including effects on bone health throughout life. Maternal vitamin D status may program neonatal skeletal development. The objective here was to determine the association of mothers' vitamin D status with bone variables of their newborns.

SUBJECTS AND METHODS: In a birth hospital, pregnant women (n = 125) participated in a cross-sectional study with a longitudinal follow-up of the pregnancy. The mean (sd) values for age, body mass index before pregnancy, pregnancy weight gain, and total vitamin D intake in mothers were 31 (4) yr, 23.5 (3.7) kg/m(2), 13.1 (4.3) kg, and 14.3 (5.8) microg, respectively. All newborns were full-term, 99% were appropriate for gestational age, and 53% were boys. Blood samples were collected from mothers during the first trimester and 2 d postpartum and from umbilical cords at birth for analysis of serum 25-hydroxyvitamin D (S-25-OHD), PTH, and bone remodeling markers. Bone variables were measured by pQCT at the 20% site of the newborn tibia on an average of 10 (11) d postpartum. Bone contour was analyzed with a single threshold of 180 mg/mm(3) for the detection of total bone mineral density (BMD), bone mineral content (BMC), and cross-sectional area (CSA).

RESULTS: Mean S-25-OHD was 41.0 (13.6), 45.1 (11.9), and 50.7 (14.9) nmol/liter during the first trimester, postpartum, and in the umbilical cord, respectively. The median value of the individual means for first trimester and the 2-d postpartum S-25-OHD was 42.6 nmol/liter, which was used as cutoff to define two equal-sized groups. Groups are called below median and above median in the text. Newborns below median were heavier (P = 0.05), and 60% were boys. Tibia bone mineral content was 0.047 (95% confidence interval, 0.011-0.082) g/cm higher (P = 0.01), and cross-sectional area was 12.3 (95% confidence interval, 2.0-22.6) mm(2) larger (P = 0.02), but no difference in bone mineral density was observed, above median compared with below median group. These results were adjusted for newborn Z-score birth weight, maternal height, and newborn age at the measurement. A positive, significant correlation was observed between remodeling markers in mothers at different time points and above median group in the cord.

CONCLUSIONS: Although the mean total intake of vitamin D among mothers met current Nordic recommendations, 71% of women and 15% of newborns were vitamin D deficient during the pregnancy. Our results suggest that maternal vitamin D status affects bone mineral accrual during the intrauterine period and influences bone size. More efforts should be made to revise current nutrition recommendations for pregnant women that may have permanent effects on the well-being of children.