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This was presented by a team from the Medical University of South Carolina (MUSC) and GrassrootsHealth during the 17th annual Vitamin D Workshop held June 2014. It was published online in The Journal of Steroid Biochemistry and Molecular Biology November 10, 2015 (open access version to follow).

Lead author, Carol L. Wagner, MD, is a professor of medicine, neonatologist, associate director of the Neonatal-Perinatal Fellowship Program and the Clinical and Translational Research Center at the Medical University of South Carolina, and the principal investigator of the Protect Our Children NOW! campaign by GrassrootsHealth.

Why is preterm birth important?

The March of Dimes estimates that the annual cost of preterm births in the United States is $12 billion (for 455,918 children). If approximately 50% of preterm births could be prevented in the general population, as this analysis suggests is possible, there could be $6 billion available for other services and, more than 225,000 children and families spared this trauma. In light of this, practice guidelines at MUSC and other institutions are currently being changed to target 40 ng/mL for pregnant women with the goal of dramatically lowering preterm birth rates.

What does this paper report?

Two vitamin D pregnancy supplementation trials were run by Dr. Wagner at MUSC: The NICHD (n=346) and Thrasher Research Fund (TRF, n=163) studies. The findings suggest increased dosages of supplemental vitamin D were associated with improved health outcomes of both mother and newborn, including risk of preterm birth (<37 weeks gestation). The key finding reported in this analysis was done by the results achieved with a given serum level.

This post-hoc analysis highlights the relationship between 25(OH)D concentration and preterm birth rates in the NICHD and TRF studies (n=509) with comparison to Charleston County, South Carolina March of Dimes (CC-MOD, n=14,609) published rates of preterm birth.

What did this paper find?

As you can see from the graph below, a 46% lower preterm birth rate was observed among women with vitamin D levels ≥40 ng/mL compared to the CC-MOD (March of Dimes) reference group. It is also interesting to note that the findings were more robust in Hispanic and Black women. This is believed to be due in large part to the change in vitamin D level. Black women entering the studies had an average vitamin D level of 16 ng/mL, and increased to an average of 30 ng/mL. Hispanics started with an average vitamin D level of 24 ng/mL and increased to an average of 38 ng/mL.  (White women started with an average of 30 ng/mL, thus leaving less room for improvement).


Another key finding is that there was a steady increase of gestation time (how long the baby stayed in the womb) correlating to the rise of 25(OH)D - but then reaching a plateau around 40 ng/mL. This adds evidence to the effort to change the standard of practice for all OBs - with a goal of getting all pregnant women at or above 40 ng/mL.

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Conclusion

In this post-hoc analysis, women who achieved a 25(OH)D serum concentration ≥40 ng/mL were observed to have a significantly lower risk of preterm birth compared to those who had concentrations of ≤20 ng/mL. These findings suggest the importance of raising 25(OH)D levels substantially above 20 ng/mL, the level currently considered sufficient by the Institute of Medicine (IOM).

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