A woman's nutritional status should be assessed preconceptionally with the goal of optimizing maternal, fetal, and infant health. Pregnancy-related dietary changes should begin prior to conception, with appropriate modifications across pregnancy and during lactation. (See "The preconception office visit" and "Initial prenatal assessment and first trimester prenatal care".)
Most nutritional advice for pregnant women is based on the 1990 Institute of Medicine (IOM) Pregnancy Report , the 2005 Dietary Guidelines for Americans by the United States Department of Health and Human Services (HHS) and United States Department of Agriculture (USDA), and the following 2006 IOM publication: Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. The Recommended Dietary Allowances (RDAs) are levels of nutrients recommended by an expert IOM panel based on extensive evaluation of available scientific evidence and mathematically adjusted to meet the needs of 97 percent of the population.
Although it is clear that prenatal nutrition impacts short- and long-term health, many scientific questions remain unanswered due to the many challenges to performing high quality scientific research in pregnancy. These challenges include the often unknown critical windows of when nutrition may impact development, many physiological changes that occur over the course of normal pregnancy, large individual differences in maternal adaptation to pregnancy, ethical and practical issues of experimenting with human pregnancy, and the lack of a good animal model that can be directly extrapolated to humans.
Nutritional concerns related to pregnancy will be discussed here. Dietary issues in nonpregnant adults are reviewed elsewhere. (See "Healthy diet in adults" and "Vitamin supplementation in disease prevention" and "Dietary and nutritional assessment in adults".)
ASSESSMENT OF NUTRITIONAL STATUS
Where available, nutritional assessment and counseling can best be performed using a team approach, including the obstetrical provider, health professionals trained in prenatal nutrition counseling and education, and a registered dietitian with perinatal nutritional expertise.