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Recent RCT discovers vitamin D deficiency may double the risk of preeclampsia in pregnant women

Posted on: October 2, 2017   by  Riley Peterson & John Cannell, MD.


Preeclampsia is a pregnancy-specific form of hypertension characterized by high blood pressure and the presence of excess protein in the urine. While preeclampsia is relatively straightforward to treat, this condition can be very dangerous for both the mother and child. This condition accounts for about 25% of all maternal deaths and increases the risk of birthing a premature and/or small for gestational age infant, both of which increase the likelihood of infant mortality.

Although all pregnant women have the potential to develop preeclampsia,, there are several factors which may increase one’s risk of this condition. Diabetes, past of chronic hypertension, chronic kidney disease, multiple-child pregnancy, family history of preeclampsia, obesity and immune disorders have been linked to an increased risk of preeclampsia. Additionally, some calcium disorders, such as vitamin D deficiency and hypocalciuria, or low calcium levels found in the urine, have been identified as major risk factors associated with the development of preeclampsia.  

Past research has discovered links between vitamin D and a variety of complications related to pregnancy and birth, including but not limited to preterm birth, small for gestational age birth, gestational diabetes, miscarriage and preeclampsia. Additionally, researchers estimate up to 82% of pregnant women are vitamin D deficient throughout the world. The effect of vitamin D deficiency on pregnancy-related conditions, such as preeclampsia, can be detrimental to both the mother and infant’s health. Therefore, researchers decided to evaluate the role of vitamin D supplementation on preventing recurrence of preeclampsia in women with a history of the condition.

Researchers included a total of 142 women with a history of preeclampsia who were receiving prenatal care from the obstetrical clinic in Besat Hospital of Sanandaj City. Women were excluded if they had vitamin D levels above 25 ng/ml (62.5 nmol/L), had chronic hypertension before pregnancy or had history of renal, cardiac or pulmonary disease. All women had their vitamin D levels tested at baseline.

Of the 142 women, 70 were administered a 50,000 IU vitamin D supplement every two weeks (intervention group) and the remaining 72 were administered a placebo pill (control group). Both the intervention and control group received their treatment until the 36th week of pregnancy.

The researchers discovered that the control group had a 1.94 times increased risk of developing preeclampsia compared to women in the intervention group (p = 0.036).

The researchers concluded:

“Vitamin D supplementation therapy in pregnancy could help in reducing the incidence of gestational hypertension/preeclampsia.”

Healthy vitamin D levels are important to maintain at this earliest phase of the life cycle. The available research has linked vitamin D deficiency in pregnancy to a myriad of adverse outcomes, some of which may stay with both mother and/or child for the remainder of their lives. Research has supported the benefits of vitamin D supplementation and/or safe sun exposure during pregnancy; therefore, it is our responsibility to advocate on behalf of science.

The Vitamin D Council recommends supplementing between 5,000-10,000 IU per day in order to attain optimal status, between 40-60 ng/ml (100-150 nmol/L). This remains true for pregnant women; however, research has supported a higher dose of vitamin D may be required for women who are breastfeeding. For this group of women, at least 6,400 IU/day may be required to maintain optimal status and to provide enough vitamin D for a breastfeeding infant.


Peterson, R. Recent RCT discovers vitamin D deficiency may double the risk of preeclampsia in pregnant women. The Vitamin D Council Blog & Newsletter, 9/2017.


Sasan, S.B. et al. Clinical Study The Effects of Vitamin D Supplement on Prevention of Recurrence of Preeclampsia in Pregnant Women with a History of Preeclampsia. Obstetrics and Gynecology International, 2017.

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