Vitamins during Pregnancy: good or bad?

By Audrey Bemis and Delilah Bennett

Finding out that you are pregnant can be exciting; however, it comes with many responsibilities. Our daily lives place us in contact with a number of risks, which may not be harmful to a normal human being, but can be very dangerous to the fetus of women during pregnancy.  These factors are also known as teratogens, or substances that may interfere with the normal development of a fetus.  Many of these teratogens are well know in today’s society, such as smoking, alcohol, and caffeine.  However, a lesser known teratogen may be specific vitamins, according to recent studies.  The American Pregnancy Association recommends that you stick with one multivitamin at a time rather than multiple supplements, sticking to the one dose within the Recommended Dietary Allowance (RDA). Two studies performed within the last five years have placed a specific emphasis on Vitamin D, indicating that it can be either a beneficial or harmful substance for a developing fetus.  Limitations of these two studies also highlight the importance of critical periods in fetal development, where certain outside factors may have a greater effect than they would if they were exposed to the fetus at another time during development.

Common perceptions of Vitamin D effects:

In the past, Vitamin D has had a good reputation among prenatal vitamins for strengthening bones, protecting against infections, and attending to the nervous and muscular systems.  It is sometimes referred to as the “sunshine vitamin,” because the body produces Vitamin D when exposed to sunlight.  In adults, deficiency of this vitamin has been shown to cause major health issues such as heart disease, certain cancers, Alzheimer’s disease, schizophrenia, and some autoimmune disorders.

Is Vitamin D safe for your baby?

In 2010, a study was conducted by Bruce Hollis and his colleagues at the Medical University of South Carolina, in which 500 women who were at least 12 weeks pregnant took either 400, 2,000, or 4,000 International Units (IU) of vitamin D per day.  These women were within the second trimester of pregnancy and beyond. Currently, the guidelines for vitamin D intake for pregnant women are between 200 and 400 IU per day, which is typically the amount of vitamin D found in most prenatal vitamins. Experts have always been wary of allowing pregnant women to consume more than this amount, as they believe that it may cause birth defects. However, the results of this study showed no problems with pregnant women consuming over the current limit of vitamin D. In fact, doubling the amount of vitamin D that pregnant women are allowed to take was not only proven to be safe, but was also proven to reduce the risk of highly dangerous complications associated with childbirth, such as going into labor early, giving birth prematurely, or catching infections.  Therefore this study affirms the idea that vitamin D is safe for your baby, and it may even be beneficial to the childbirth process. Another study conducted in Germany, however, contradicts this idea.

In a study carried out by the Helmholtz Centre for Environmental Research in Germany, 622 mothers had Vitamin D levels in their blood and the cord blood of their fetuses tested in order to determine if these concentrations correlated with the prevalence of food allergies suffered by the infant in its first few years.  The researchers found that there was, in fact, a pattern because where expectant mothers had lower levels of Vitamin D in their blood, it was also rarer that their two-year old child later had food allergies.  They point at the fact that there are many other factors that could contribute to food allergies, but they found a definite correlation between Vitamin D levels and their later emergence.  They point to the higher levels of a specific immunoglobulin E to food allergens like eggs, milk, wheat, and soy.   Ultimately, the researchers in this study discourage pregnant mothers from taking Vitamin D supplements.

When considering these studies, it is important to realize the limitations of each, and point out that there is most likely a critical period during which overexposure to Vitamin D is most harmful to the growing fetus.  In the first study, the women were all in their second trimester or beyond, so there is not evidence as to whether or not Vitamin D is harmful or helpful earlier on in a pregnancy, when the fetus is developing its major organs.  The second study only measured the connection between Vitamin D and food allergies, which also have a number of contributing factors.  These allergies were measured via a questionnaire given to mothers during the child’s first two years of life, while some allergies develop later on in childhood or adolescence.  It is also significant to remember that Vitamin D levels outside of diet are often linked to sun exposure, so it is not just about what you consume.

Moving forward

Given this information, it is important as an expectant mother to be mindful of what you are giving your unborn baby with regards to vitamins and many other substances.  A fetus has many different stages of development in the womb, during which outside factors can cause health defects if not monitored carefully.


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