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Low Vitamin D in Pregnancy

Vitamin D is receiving a large degree of publicity due to ongoing research and more information arising about multiple problems due to low levels of vitamin D in most adults. Vitamin D has been shown to help maintain muscle and bone health, and is now being associated with hormonal function, heart, liver, kidney and brain health. Low levels of vitamin D are also associated with an increased risk of diabetes, heart disease and certain types of cancers. Muscle weakness and osteoporosis may develop at younger ages as well. Studies have shown that approximately 60-70 percent of adults in the U.S. are deficient in vitamin D.

In pregnancy, it is recommended to test for low vitamin D levels, and to treat when necessary. Testing is simple and can be done at the same time as prenatal laboratory tests. Results of laboratory tests for vitamin D vary according to the type of testing, but in our area most of the tests find that the normal levels are 30-100 ng/ml, with the optimum level between 40-90 ng/ml. Prenatal vitamins contain only 400 IU of vitamin D but studies have shown that a pregnant woman should take 2,000-4,000 IU of vitamin D throughout the pregnancy. Each 1,000 IU of vitamin D that you take will raise the blood level by 10 ng/ml. Extensive research in pregnancy has shown that vitamin D supports immune function, healthy cell division and bone health in the mother and fetus. A study from the Medical University of South Carolina revealed that pregnant women taking 4,000 IU of vitamin D daily in the second and third trimesters showed no evidence of harm, and had half the rate of pregnancy-related complications such as gestational diabetes and preeclampsia.

What risks have been associated with low vitamin D in pregnancy?

  • Low birth weight in the infant studies have shown that babies born to mothers with low vitamin D levels have a risk of lower birth weight than babies born to mothers with normal vitamin D levels. A study reported by the National Institute of Health in early January 2013, indicated that women with a vitamin D deficiency in the first 14 weeks of pregnancy had a two fold risk of delivering a baby with a weight in the 10th percentile for growth. These babies who are born with low birth weight have an increased risk of heart disease, high blood pressure and diabetes later in life according to a study by the University Of Pittsburg School of Public Health.
  • Higher risk of gestational diabetes, pregnancy induced hypertension and preeclampsia.
  • A study in India reported in 2011 showed that children born to mothers with low vitamin D, by age five had less lean muscle and by age nine had more insulin resistance. The results were identical between boys and girls.
  • In obese women at the start of pregnancy, studies have shown less transfer across the placenta with lower levels of vitamin D. Studies at Northwestern University School of Medicine showed that the babies had less body fat and lower vitamin D levels at birth. It questioned whether these babies would be at higher risk of obesity later in life.
  • Possible decrease in brain development and motor skills A study from Spain found that children of mothers with low vitamin D in pregnancy had lower mental and psychomotor development scores at 14 months of age. The study suggested that the lower scores could lead to lower IQs in the children and decreased language development. A difference between four to five points on the development scores could reduce IQ scores by up to fifty percent. An Australian study reported in 2012 showed that children of vitamin D deficient mothers had more language difficulties, with a two fold increase in poor language development. Behavioral problems were reported in a higher degree but may have been due to the difficulty with language and communication abilities.
  • Decreased immunity and increased risk of infections Studies have strongly suggested increased risk of respiratory infections in children.
  • Multiple sclerosis A study done by Queen Mary University of London reported that children born to women with low vitamin D had higher risk of multiple sclerosis in adulthood when they were born in April after the long cold winter than in November after the warm summer and fall.

All of the data is recently reported and therefore may still need to further examined, but it may be helpful to proceed with testing pregnant women for vitamin D early in pregnancy or prior to pregnancy. Once the woman is on a supplement it should be used throughout the pregnancy. If you have concerns, discuss them with your doctor.