Prenatal vitamins: a review of the literature on benefits and risks of various nutrient supplements
Pregnancy represents a time of rapid change in maternal physiology and nutritional requirements. Most pregnant women take a daily prenatal vitamin, but advising the patient can be difficult because so many different formulations are available. Vitamin and mineral supplements cannot replace a healthy diet, and there are not enough high-quality data to recommend multivitamin supplements for all American women. Folic acid is the 1 vitamin for which definitive evidence supports preventive supplementation in the periconceptional period. This article reviews the evidence in support of supplemental vitamin use during pregnancy. The discussion focuses primarily on data retrieved from the developed world, because the nutritional challenges of the developing world are distinct.
Most pregnant women take a daily prenatal vitamin, but advising the patient can be difficult because so many different formulations are available.
Prenatal vitamins generally contain a variety of vitamins and minerals and may be similar to multivitamins used outside of pregnancy, with some notable differences. Some of these vitamins have been studied directly (eg, folic acid), and their recommended allowance comes from sound evidence. But for most vitamins, data are limited, and for multivitamins (also referred to as multimicronutrient supplements), study results can be biased by confounding variables. This article reviews the evidence in support of supplemental vitamin use during pregnancy. The discussion focuses primarily on data retrieved from the developed world, because the nutritional challenges of the developing world are distinct.
GENERAL NUTRITION REQUIREMENTS DURING PREGNANCY
Pregnancy represents a time of rapid change in maternal physiology and nutritional requirements. These changes allow the mother to meet the needs of the growing fetus and placenta and occur within weeks of the establishment of pregnancy. Dietary recommendations during pregnancy have focused on maintaining adequate caloric intake while avoiding substances that may harm the growing fetus. A particular focus on micronutrients during pregnancy has led to specific recommendations regarding nutrients such as calcium, folic acid, and iron.
Since 1997, the Institute of Medicine's (IOM) Food and Nutrition Board has been publishing dietary reference intakes (DRIs) for healthy people throughout the life stages, including pregnancy (Table 1, page 78).1 These tables include recommended daily allowances (RDAs) for which the committee believed there was enough information to make such a recommendation. In some circumstances, the Food and Nutrition Board did not have enough data to determine RDAs, and therefore, the available information combined with expert opinion, was used to develop adequate intake values. The American College of Obstetricians and Gynecologists (ACOG) has incorporated these tables into its recommendations for nutrition during the perinatal period. (2)
SPECIFIC VITAMIN REQUIREMENTS
The naturally occurring, water-soluble vitamin folate is integral to the synthesis and maintenance of DNA, metabolism of amino acids, production of red blood cells, and growth of the fetus and placenta. (3) Folate is found in a number of foods and is most readily acquired from green leafy vegetables (ie, foliage), which gave it its name. (3) Folic acid is a synthetic compound that is used as a folate supplement in various...