Maternal and infant vitamin D status during the first 9 months of infant life-a cohort study.

Objective: The objective of this study was to assess vitamin D status and possible consequences of low plasma 25-hydroxyvitamin D (25OHD) levels in a population of healthy mothers and their infants.

Methods: A total of 107 women aged 24-41 years gave birth to 108 infants. They were followed up three times during 9 months.

Results: Cord blood 25OHD level (43.3 ± 20.4  nmol/l) on average was 62 ± 16% of maternal levels (73.3 ± 30.7  nmol/l), measured 1-2 weeks postpartum. Cord blood 25OHD correlated positively with maternal 25OHD levels (r=0.83, P<0.001). At birth, 23% of mothers and 61% of infants had 25OHD <50  nmol/l. Vitamin D deficiency (25OHD<25  nmol/l) was present in 66% of the children born by mothers with 25OHD levels below 50  nmol/l (P<0.01), whereas only one child was born with deficiency among mothers with 25OHD >50  nmol/l. During follow-up, most of the children (>85%) had 25OHD levels >50  nmol/l, which most likely was attributable to the use of supplements, as more than 95% of the children were given daily vitamin D supplements of 10  μg of vitamin D.Cord blood parathyroid hormone levels were very low (median 0.21; interquartile range 0.11-0.33  pmol/l), with increasing levels (P<0.01) reaching 3.08 (2.67-3.92  pmol/l) at the last visit. Vitamin D levels were not associated with anthropometric indices of the newborn infant or their growth during follow-up.

Conclusions: Vitamin D deficiency is widespread in newborn. Maternal 25OHD levels above 50  nmol/l are needed to prevent vitamin D deficiency among newborn.