Warning: Avoid Large Doses Of Vitamin A During The First Trimester
Vitamin A in large doses is a potent teratogen (causing abnormalities in the fetus). Women who take mega doses of it during the first trimester greatly increase their risk of delivering babies with a suite of defects. Two prescription drugs on the market are synthetic analogs of vitamin A, and they are teratogenic, even when taken at their prescribed doses. These drugs are isotretinoin (brand name Accutane), which is used to treat severe acne, and etretinate (brand name Tegison), which is used to treat psoriasis.
Infants born to mothers who take these drugs during the first trimester are at very high risk of suffering facial malformations, heart problems, and mental retardation. Both drugs come with clear warnings on their packages and package inserts about the dangers they pose to embryos. Women of reproductive age who are taking Accutane are advised to use two methods of birth control to make absolutely sure that they do not get pregnant while on the drug and to wait at least one month after stopping the drug before they try to get pregnant (more cautious women may want to wait more than one month). Women taking Tegison, however, need to wait much longer after discontinuing the drug and before trying to conceive because it is eliminated from the body extremely slowly. Women taking either drug and planning to conceive should consult with their OB/GYN about a safe waiting period.
Vitamin A, however, is essential for an embryo's development. Therefore, it's important that a first-trimester woman consume the right amount of it. (Vitamin A deficiency is rare in the United States and other industrialized countries.) Many fruits, vegetables, fish, and liver contain vitamin A and/or beta-carotene (the body converts beta-carotene to vitamin A when needed).
Since beta-carotene and vitamin A differ in potency, their amounts are not expressed in units of weight but are converted to units of common potency known as retinol equivalents (RE) or "international units" (IU). The RDA of vitamin A for pregnant women is 800 RE, and the U.S. RDA is 8,000 IU (which equals 2,400 RE when the source is pure vitamin A rather than beta-carotene). Whereas large doses of vitamin A are not considered safe for adults or embryos, large doses of beta-carotene are thought to be relatively safe. Thus, a first-trimester woman who eats plenty of vitamin A and also wants to take a multivitamin supplement may want to choose one whose main source of vitamin A is beta-carotene rather than preformed vitamin A. Liver often has such high levels of vitamin A that it probably should not be eaten regularly by a first-trimester woman.
