Vitamins, taken in normal quantities, are essential to your survival. Taking too many vitamins -- especially fat-soluble ones, which accumulate in fatty tissues in the body -- can cause health problems. During pregnancy, high levels of vitamins A and D can have teratogenic effects, meaning that they can cause birth defects in the developing fetus.
Timing
Taking high doses of vitamins at the beginning of pregnancy -- as early as the first 10 to 14 days, when you may not even realize that you are pregnant -- can increase the risk of birth defects, according to the Children's Hospital of Wisconsin. The major organs and limbs form during the first 12 weeks of pregnancy, making this time particularly dangerous for some type of malformations. A woman of childbearing age should not take megadoses of vitamins if she could possibly become pregnant. She also should not take acne medications that contain vitamin A in the form of retinol, unless there is no chance she will become pregnant.
Vitamin A
Most of the teratogenic effects of vitamin A have occurred in women taking anti-acne medications containing isoretinin. Malformations occur in as many as 20 percent of the children born to women taking the medication in early pregnancy, according to studies reported in the April 1982 "Journal of the American Academy of Dermatology." The malformations occurred in one of four areas: the cranium and face, the heart, the thymus or the brain. The risk of malformations in exposed fetuses was 26.5 times the risk of those with no exposure to excessive amounts of vitamin A. Mothers were taking doses of 0.5 to 1.5 mg/kg/day, reports the Illinois Teratogen Information Service. Doses of vitamin A higher than 8,000 International Units, or IUs, are not advised during pregnancy.
Vitamin D
Extremely large doses of vitamin D during pregnancy -- up to 1,000 IUs per kilogram of body weight -- may cause fetal malformations, according to pharmacist Razak Lajis at the National Poison Centre in Malaysia. Infants born to mothers with high levels of vitamin D may develop suppression of the parathyroid gland at birth, with low calcium levels and seizures.
Considerations
Unless you have a serious vitamin deficiency that needs physician treatment, you do not need to take excessive amounts of vitamins. Do not take more than the standard prenatal dose of any vitamin unless specifically told to do so by your physician. Women taking products containing vitamin A should take precautions to ensure that they will not get pregnant during treatment. Waiting until you know you are pregnant may be too late to prevent fetal malformations.
References
- Illinois Teratogen Information Service; Vitamin A and Pregnancy; Eugene Pergament, et al.; March 1996
- "Journal of the American Academy of Dermatology"; Toxicology, Carcinogenicity, and Teratogenicity of Some Orally Administered Retinoids; J. Kamm; April 1982
- National Poison Centre, Universiti Sains Malaysia; Effects of Vitamin D Overdose; Razak Lajis; 1996
- Children's Hospital of Wisconsin: Teratogens
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