Bone turnover and maternal 25(OH) vitamin D3 levels during pregnancy and the postpartum period: should routine vitamin D supplementation be increased in pregnant women?

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Objective To investigate the relationship between 25(OH) vitamin D3 levels and maternal bone turnover during pregnancy and lactation. Study design Thirty pregnant women and 30 healthy non-pregnant controls were included the study. The pregnant women were examined in the 12th, 25th and 32nd gestational weeks and 6 weeks after delivery. The controls were examined once. Serum concentrations of 25(OH) vitamin D3, parathyroid hormone (PTH), cross-linked C-terminal telopeptide of type I collagen (CTX), calcium, and phosphate were measured. Results In the 32nd week and the postpartum period, 25(OH) vitamin D3 deficiency rates were 13.3% and 33.3%, respectively. Serum 25(OH) vitamin D3 levels were below the detection limit in 10% and 33%, respectively, of the same subjects. In the control group, rates of 25(OH) vitamin D3 deficiency and “below detection limit” were 30% and 23%, respectively. While 25(OH) vitamin D3 and CTX levels were not correlated to each other in the first trimester, a negative correlation was found in the 2nd and 3rd trimesters and the postpartum period between 25(OH) vitamin D3 and CTX levels ( r = −0.472, p = 0.048; r = −0.893, p < 0.0001, r = −0.881, p < 0.001, respectively). No correlation between 25(OH) vitamin D3 and CTX levels was found in controls. Conclusion We consider that 25(OH) vitamin D3 supplementation of women could both decrease maternal bone resorption and lead to enhanced bone mass in offspring during later life. Since women are prone to 25(OH) vitamin D3 insufficiency, we suggest higher doses of 25(OH) vitamin D3 should be given to pregnant subjects.