Obese Mamas Pass Along Less Vitamin D

Obese pregnant women may provide less vitamin D to their newborns

/ Author:  / Reviewed by: Joseph V. Madia, MD

(RxWiki News) Pregnant women are advised to take prenatal vitamins to ensure they get all the nutrients they need. But their weight may play a role in how many of those nutrients reach their baby.

A recent studied looked at the levels of vitamin D found in newborns. The researchers found that obese women's babies had lower vitamin D levels than babies of leaner women.

This result occurred despite the fact that both groups of women had similar vitamin D levels themselves.

"Ask your OB/GYN about weight goals."

The study was led by Jami L. Josefson, MD, of the Division of Pediatric Endocrinology at Ann and Robert H. Lurie's Children's Hospital of Chicago.

The researchers measured the vitamin D levels in 61 women and/or their newborns. They divided the women according to whether they had a healthy weight or were obese and ended up with data from both the babies and the mothers in 45 mother-child pairs.

The researchers found that all the women had similar levels of vitamin D when they were assessed at 36 to 38 weeks of pregnancy. The obese women had an average of 49.84 ng/ml, compared to 46.05 ng/ml in the women of a healthy weight.

These vitamin D levels were sufficient for the women. They were not deficient, regardless of their weight.

However, the researchers did find differences among the babies when they tested the vitamin D levels in the blood of the newborns' umbilical cords.

The mothers with a healthy weight had babies with more vitamin D than the babies of obese mothers. The average level among babies of healthy-weight moms was 27.45 ng/ml, compared to 20.81 ng/ml in babies of obese moms.

The researchers found four factors that appeared linked to the lower levels of vitamin D in the children of obese mothers. One was the fact that the mothers were obese, but the mothers' age, the mothers' vitamin D levels and the babies' level of fat mass also played a part.

Every additional year in age of the mothers translated to about 0.6 ng/ml more vitamin D in the newborns' cord blood.

For every additional 1 ng/ml the mother had of vitamin D, her baby had about 0.32 ng/ml additional vitamin D in the cord blood.

Then, for each additional percentage point of body fat in the newborns, they had an additional 0.7 ng/ml of vitamin D in their cord blood.

However, the presence of obesity in a mother was by far the biggest influence on the newborns' vitamin D levels, reducing them by about 6 ng/ml.

The researchers determined that obese women seemed to hang on to more of their vitamin D, even though they appeared to be getting enough through prenatal vitamins.

"It's possible that vitamin D may get sequestered in excess fat and not transferred sufficiently from an obese pregnant woman to her baby," Dr. Josefson said in a statement about the study.

"These findings underscore the importance of understanding the evolving relationships between maternal obesity, vitamin D nutritional status, and adiposity in the neonatal period, childhood, and adulthood," the researchers concluded in the study.

The authors did not note whether the vitamin D levels in the newborns' cord blood was insufficient or not, though they noted that vitamin D deficiency in general in children and adults is linked to obesity, higher fat levels and insulin resistance (which is linked to diabetes).

Further research is necessary to determine what these findings mean for pregnant women, but the researchers noted that "obese women may need larger amounts of vitamin D supplementation to provide their neonates with sufficient levels of vitamin D."

Pregnant women should thoroughly discuss the risks and benefits of any vitamin supplementation with their doctor before starting a regimen.

The research was published January 4 in the Journal of Clinical Endocrinology and Metabolism. The research was funded by the Diabetes in Pregnancy Program grant sponsored by Northwestern Memorial Hospital, the Eleanor Wood Prince Grant Initiative, the National Institutes of Health and a Cooperative Research Agreement between Ann & Robert H. Lurie Children’s Hospital of Chicago and the Williams Heart Foundation. The authors declared no conflicts of interest.

Reviewed by: 
Review Date: 
January 26, 2013
Last Updated:
January 29, 2013