Pre-eclampsiaPatient friendly summary

  • Solar UVB light may reduce the risk of pre-eclampsia by producing vitamin D.
  • Higher vitamin D levels may be associated with a lower risk of pre-eclampsia.

Pre-eclampsia is a serious condition that may occur late in pregnancy.

The blood pressure increases, and protein is excreted in the urine. Blood flow to the placenta (lining of the uterus) may be reduced.

Pre-eclampsia may create problems for the mother and baby.

Risk factors

The exact cause of pre-eclampsia is unknown. Possible causes include:

  • Autoimmune disorders
  • Blood vessel problems
  • Diet high in sugar and polyunsaturated fats
  • Genetics
  • Diabetes

Sunlight exposure and pre-eclampsia risk

Many international studies report a higher risk of pre-eclampsia after a summer conception and with expected winter delivery. Vitamin D levels are lowest in the winter.

Vitamin D and pre-eclampsia

Vitamin D levels

Studies found a connection between vitamin D blood levels and pre-eclampsia:

  • U.S. women with vitamin D levels lower than 20 ng/mL (50 nmol/L) were two to four times more likely to have pre-eclampsia compared to women with adequate levels.
  • Babies born to women with pre-eclampsia were twice as likely to have vitamin D levels below 15 ng/mL (37.5 nmol/L). 
  • In South Carolina, women with early-onset severe pre-eclampsia had lower vitamin D levels than healthy controls.

How vitamin D works

Vitamin D may reduce the risk of pre-eclampsia because it:

  • Increases the level of growth factor in the blood of the fetus (growth factor helps the body grow.);
  • Lowers blood pressure.


Several studies addressed vitamin D and the prevention of pre-eclampsia:

  • At 20 weeks gestation, women who took halibut liver oil supplements (900 IU [23 mcg]/day vitamin D) were 32% less likely to develop pre-eclampsia. (These women also took other vitamins, minerals, and fish oil.)
  • Pregnant women in South Carolina took 6400 IU [160 mcg]/day vitamin D3. None of the women developed too much calcium in the blood or urine. This is a concern with high intakes of vitamin D
  • Early intake of vitamin D may actually prevent pre-eclampsia years later. A Finnish study researched women who received 2000 IU/day of vitamin D during their first year of life. Many years later, these women had half the risk of developing pre-eclampsia. Vitamin D may have enhanced their immune systems.

Vitamin D plus calcium

According to one study, at 20–24 weeks gestation, women who took vitamin D (1200 IU [30 mcg]/day) plus calcium (375 mg/day) had significantly lower blood pressure compared to women taking a placebo treatment.


Vitamin D3 (cholecalciferol) may be beneficial for women with pre-eclampsia. Large doses of vitamin D3 for a few days (50,000 IU [1250 mcg]/day) will quickly increase vitamin D levels. The doses can be lowered after that to about 6000 IU.

It is important for pregnant women to discuss vitamin D supplements with their doctor. However, many doctors are not up on the latest vitamin D research. It would be worthwhile to bring some literature on vitamin D to the doctor.

Find out more...

Do you want to find out more and see the research upon which this summary is based?  Read our detailed evidence summary on Pre-eclampsia.

Page last edited: 06 May 2011