According to researchers from the University of Pittsburgh, pregnant women with lower than normal vitamin D levels during pregnancy are more likely to give birth to infants falling into the low birth weight category. Funding for the research was provided by the National Institutes of Health.

Data was collected from 2,146 women was agreed to be part of the Collaborative Perinatal Project. The project collected data between 1959 and 1965. Despite more than 50 years passing, in some cases, the blood samples were preserved well enough for researchers to test vitamin D levels.

Of the blood samples tested, women who tested with vitamin D levels below 37.5 nmol/L were more likely to given birth to infants weighing about 46 grams less than peers born to mothers without vitamin D deficiency. If the deficiency was found during the first 14 weeks of gestation, infants were twice as likely to fall at or below the 10th percentile for weight.

The impact of low birth weight immediately affects an infant’s health, in some cases, but there are also potential long-term side effects. Infants born in the low birth weight or very low birth weight categories are more likely to suffer heart disease, type 2 diabetes and/or hypertension. The connection between pregnancy health, infant health, and long-term adult health are just being discovered and reported so there could be additional side effects.

The connection between vitamin D deficiency and low birth weight is not clear, but researchers believe there could be issues with fetal bone development or hormone levels associated with calcium uptake. Vitamin D plays an important part in calcium absorption and utilization.

Doctors and researchers believe the results of the study provide insight into the importance of vitamin D in pregnancy diets, but there could be a few issues with the participant population when compared to women today. During the six-year span when blood samples were taken, women weighed less and smoked more than women today. Sunscreen use was not as prevalent and there were fewer foods enriched with vitamin D. A modern blood sample pool could provide a more accurate analysis of vitamin D levels in today’s pregnant population.

Source: Lisa M. Bodnar Ph.D., MPH, RD, Hyagriv N. Simhan MD, Mark A. Klebanoff  MD, MPH. Low Vitamin D Levels Early in Pregnancy Associated with Lower Birth Weights. University of Pittsburgh Graduate School of Public Health. 19 December 2012.