Public health policy should be reconsidered concerning the use of vitamin and mineral supplements by all women -- from their teen years to menopause -- who may eventually bear children, recommends Carl Keen, chair of the UC Davis nutrition department and an authority on nutrition and human development. "Research findings indicate that the risk of certain birth defects can be dramatically lowered by enhancing the nutritional status of the mother prior to and after conception," says Keen. "Since laboratory studies on animal models indicate that nutritional deficiencies have profound effects on the health of the fetus very early in conception, it's advisable that a woman already be regularly taking supplements at the time of conception, rather than waiting until she realizes that she is pregnant," he says. Keen's overview of previous studies on maternal nutrition and pregnancy, which appears in a special February issue of the American Journal of Clinical Nutrition, cites evidence indicating the importance of nutrition in preventing neural tube defects, cleft lips, cleft palates and cretinism.