During pregnancy, the fetus is very vulnerable to toxins in the uterine environment. Substances such as certain vitamins may be completely harmless to the mother, but could have disastrous effects on the development of the fetus. These kinds of birth defects can be prevented when the mother knows the potential danger of the specific vitamins and how dangerous levels of these vitamins could be avoided.
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Vitamin A Toxicity
Vitamin A consumption should be carefully monitored during pregnancy, especially in the first trimester. Vitamin A is a fat soluble vitamin, which means that when it is consumed in excessive amounts it is stored in the body's fatty tissues rather than being excreted harmlessly in the urine. Unfortunately, this vitamin A buildup can have toxic effects on the developing body of the fetus. Vitamin A is essential for healthy vision and effective decoding of genetic information and is vital for fetal development. However, excessive quantities have been found to cause major malformations in one-fifth of fetuses exposed during the first trimester.
Sources of Excessive Vitamin A
Vitamin A can be found in anti-acne medications such as Accutane and Retin-A. Accutane in particular has been associated with a 26-times-higher chance of head, face and brain malformations, heart defects and malformations of the thymus gland. There appears to be a direct relationship between quantity of vitamin A consumed and severity of malformations; that is, more vitamin A seems to lead to more serious malformations.
Recommended Intake of Vitamin A
At present, it seems that consumption of up to 8,000 International Units of vitamin A per day does not cause malformations of the fetus. The Institute of Medicine recommends specific tolerable upper levels for vitamin consumption during pregnancy. The tolerable upper intake level of vitamin A is 2,800-3,000 mcg per day.
Vitamin D Toxicity
The other vitamin that is thought to be harmful to the fetus is vitamin D. An overdose of vitamin D has been found to lead to malformation of the heart valves in the fetus and is hypothesized to lead to miscarriage when taken in exceptionally large quantities.
Vitamin D Deficiency
However, darker skinned or veiled women are at an increased risk of being deficient in vitamin D compared to white women during pregnancy. Vitamin D deficiency can lead to smaller, lighter babies, with brittle bones and inadequate tooth enamel mineralization. Women who are unlikely to be able to make sufficient vitamin D through sun exposure are recommended by the Committee on Medical Aspects of Food and Nutrition Policy to take a 10 mcg supplement of vitamin D daily. The Institute of Medicine recommends a maximum intake level of 50 mcg for vitamin D during pregnancy.