The objectives of this pilot study were to examine the diets of pregnant women and healthy women of childbearing age, to quantify their diets using the US Department of Agriculture Healthy Eating Index (HEI), and to assess the validity of the HEI in pregnancy in terms of macronutrients and micronutrients. Dietary information was prospectively collected from nonpregnant women and pregnant women at 20 to 38 weeks' gestation using 4-day food records. Diet records were analyzed for nutrient content using computer software and for overall quality using the HEI. Differences between the groups were analyzed statistically using the Student's t test, descriptive statistics, and chi 2 analysis. The macronutrient composition of the diets and the number of food group servings were similar in both groups. The HEI scores for control (nonpregnant) and pregnant women were similar, 72.6+/-1.52 and 75.0+/-0.99, respectively, of a maximum possible score of 100. Pregnant women did not meet daily recommended intakes of micronutrients of concern in pregnancy (calcium, iron, folate) through dietary means. Dietary counseling and nutritional supplements (particularly iron and folate) may be necessary. The HEI was useful in providing a composite measure of dietary intake, but did not discern the need for vitamin and mineral supplements during pregnancy.