How Does Vitamin D Deficiency Affect Risk of Pregnancy Complications?
Pregnancy is not a disease. Nevertheless, it is associated with increased risk to the health of the expectant mother, which can in turn affect the unborn child. Regular visits with trained professionals can help to identify and reduce some of the risks of pregnancy. Nutrition is considered to be a modifiable factor that can affect the progress or outcome of a pregnancy. For example, adequate folate levels prevent neural tube defects. Another area of active research is the effect of vitamin D on hypertension-related complications such as pre-eclampsia. The research group led by Reeves recently looked at whether vitamin D deficiency, which is particularly prevalent in minority populations in the United States, was a risk factor for certain pregnancy-related conditions.
Vitamin D affects many systems within the body. The placenta contains vitamin D receptors, which means that vitamin D levels can affect how the placenta functions (see review from Barrett and McElduff). In addition, low levels of vitamin D have been identified as a potential cause of hypertension and diabetes. The current study investigated whether vitamin D levels were associated with two of the most common pregnancy-related complications, pre-eclampsia (which affects 5-8% of pregnancies) and gestational diabetes (affecting up to 9% of pregnancies).
The authors looked at newborn umbilical cord blood vitamin D concentrations in a group of 47 mother-infant pairs from ethnic minorities. Newborn cord blood reflects the vitamin D levels of both the infant and its mother. The authors used two cut-off points for vitamin D deficiency. The lowest cut-off was the study median of 16 ng/ml, and the authors also defined an cut-off point of 25 ng/ml, apparently based on information from the Institute of Medicine about sufficient population vitamin D levels. Around 80% women in the study vitamin D levels below the cut-off of 25 ng/ml. Low vitamin D was more likely in women aged under 30, and in women with a BMI above 30 (obesity).
The authors found that low vitamin D levels were associated with a tripling in risk of gestational diabetes. In addition, all women who had chronic hypertension had low levels of vitamin D. Hypertension that developed during pregnancy was more likely in minority women with low vitamin D levels, as well. The authors also linked gestational hypertension with a 12-fold increased risk of pre-eclampsia. It seems that high blood pressure that develops during pregnancy predisposes women to pre-eclampsia. If vitamin D is capable of reducing or normalizing blood pressure, it is possible that an adequate vitamin D status could reduce risk of pre-eclampsia in pregnancy.
This study was rather small, and the results by themselves cannot be applied to the wider population. Even so, as ethnic minorities tend to be at higher risk of vitamin D deficiency, this study attempts to address a research need in a specialized population.
Reeves IV, Bamji ZD, Rosario GB, Lewis KM, Young MA, Washington KN. Vitamin D deficiency in pregnant women of ethnic minority: a potential contributor to preeclampsia. J Perinatol 2014;34(10):767-73. doi: 10.1038/jp.2014.91
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