Nutritional Supplements in Pregnancy: Too Little and Too Much, 2/1996 

The pregnant woman needs to consider both her own requirements and the requirements of her baby when thinking about nutrition and nutritional supplements. Vitamins are needed during pregnancy for the maintenance of the mother's health, to support the developing infant's growth, and to help prevent developmental defects. However, vitamins taken as a dietary supplement are not innocuous and the infant's genetic makeup and the environment provided by the mother are essential for their appropriate utilization. Excessive amounts of some vitamins may increase the occurrence of a developmental defect, inadequate amounts can predispose to a developmental defect. A great deal has been written about this and physicians usually provide the necessary information to an expectant mother during pre-natal care visits. 

During this past year, additional information has become available about two nutrients, both usually recommended by physicians to pregnant women as supplements to a "normal American diet". However, the best source of any nutrient is food; supplementation by pills can be very useful if done properly, but it can also be dangerous if done poorly.¹ 

Two nutritional supplements about which new information is available are: 

1. TOO LITTLE - Folate (folic acid): There is now substantial evidence that during early pregnancy (the first several weeks), an additional intake of folic acid (a B vitamin) can help prevent defective development of the spinal cord (spina bifida) and of the brain (anencephaly) in infants with a predisposition to these abnormalities. The problems are: (a) recognition of pregnancy in these critical early weeks and (b) who is predisposed? During the first several weeks of pregnancy, critical areas of the brain and spinal cord of the infant are developing. Sufficient amounts of a nutrient, folic acid, is essential at this time. This is particularly important when there is a family history of either spina bifida or anencephaly.

   Since folic acid is important very early in pregnancy, it is recommended by the U.S. Public Health Service that women who are either considering having children or who are at risk of becoming pregnant accidentally discuss their needs for supplemental folic acid with their physicians. Supplementation can be by vitamin pill and/or by diet. Foods rich in folic acid are cereals, lentils, dark green leafy vegetables, chicken and beef liver, and orange juice.

2. TOO MUCH - Vitamin A: Vitamin A is essential for fetal growth and development, particularly of the nervous system, heart and face. Vitamin A and a Vitamin A source -- beta carotene, are usually present in a wide variety of commonly eaten foods. However, too much Vitamin A can lead to serious developmental defects. This is particularly true if excess amounts of Vitamin A in vitamin supplements are taken early in pregnancy. How much is too much? How much is too little? These questions are still being explored. It is suggested by experts that women who plan to become pregnant, are subject to becoming pregnant, or who are pregnant need to discuss their Vitamin A needs with their physician.

Discussion:
At this time, indiscriminate use of vitamin supplements for women who are pregnant can be dangerous to their infants; dangerous because they may not be getting enough of a needed vitamin (folic acid) or too much of a vitamin also needed (Vitamin A). In very general terms, a multi-vitamin tablet containing 0.4 mg of folic acid and no more than 8,000 IU of Vitamin A daily is being recommended by the experts. More important, it is extremely important that women before becoming pregnant or very early in their pregnancies talk to their physicians about their own specific needs and not "vitamin pill pop" indiscriminately.
 

¹ Rothman, K.J. et al; Teratogenicity of High Vitamin A Intake; NEJM, 1995; 333: 1369-1373; 1414-1415
 

© UCP Research & Educational Foundation, February 1996

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