As per a study based on the Maternal Vitamin D for Infant Growth (MDIG) trial in Dhaka, Bangladesh, high-dose prenatal vitamin D supplementation can reduce bone resorption during pregnancy, even though the effect is limited to one biomarker and does not continue postpartum, as published in ‘Endocrine and Metabolic Science’ journal. These findings highlight the complex relationship between vitamin D and maternal bone health during and after pregnancy.

This study led by Christine Krupa examined the impact of vitamin D3 (cholecalciferol) supplementation on bone formation and resorption biomarkers at delivery and after 6 months postpartum. Overall, 1300 females having uncomplicated singleton pregnancies in the MDIG study underwent randomization to get a prenatal; postpartum regimen of placebo or vitamin D3, as shown below:

• Group A: 0;0 International Units (IU) vitamin D3 per week
• Group B: 4200,0 IU vitamin D3 per week
• Group C: 16,800;0 IU vitamin D3 per week
• Group D: 28,000;0 IU vitamin D3 per week
• Group E: 28,000;28,000 IU vitamin D3 per week

This randomization occurred from 17 to 24 weeks gestation and continued until 6 months after childbirth. The sample for analysis comprised MDIG participants (n=690; 53% out of 1300 trial participants) who had available data for a minimum of one biomarker of interest at either delivery or after 6 months, along with an equivalent baseline measurement. Maternal venous blood samples obtained at enrollment, delivery, and 6 months postpartum were analyzed for biomarkers associated with bone turnover. These included receptor activator nuclear factor-kappa B ligand; fibroblast growth factor-23; osteoprotegerin and osteocalcin (inflammatory biomarkers); procollagen type 1 N-terminal amino-terminal propeptide; and serum carboxy-terminal telopeptide of type 1 collagen (Ctx).

The percentage differences between the vitamin D group and the placebo, along with 95% confidence intervals (95% CI) were presented as effects of the supplementation. Out of the 690 volunteers, 64% displayed 25-hydroxyvitamin D concentrations (25OHD) less than 30 nmol/L and 94% revealed 25OHD less than 50 nmol/L at the time of enrollment in this trial. At delivery, the mean concentrations of CTx were 27% lower in group E compared to the placebo.

But, at 6 months postpartum, the concentrations of CTx were not substantially different in group E as opposed to placebo, taking into account the concentrations of CTx at the time of delivery. Outcomes on other biomarkers at delivery or postpartum were not noteworthy. Thus, prenatal supplementation with 28,000 IU of vitamin D3 per week led to a reduction in CTx levels at delivery compared to a placebo.

This effect was linked with a drop in parathyroid hormone. However, the impact of elevated dose vitamin D on CTx did not sustain at 6 months postpartum. Thus, high-dose prenatal vitamin D reduces bone resorption during pregnancy, but evidence for sustained postpartum benefits requires further research.