This study compared nutritional intake during pregnancy among women of Mexican descent according to country of birth (US vs. Mexico) and, for Mexico-born women, according to number of years lived in the US (<or=5 years, 6-10 years, >or= 11 years). A 72-item food frequency questionnaire (FFQ) was used to assess dietary intake in 474 pregnant Mexico-born immigrants and US-born Mexican-Americans. Mexico-born women had significantly higher intakes of calories (P = 0.02), fibre (P < 0.001), vitamin A (P < 0.001), vitamin C (P = 0.03), vitamin E (P < 0.01), folate (P < 0.01), calcium (P < 0.001) and zinc (P = 0.02) from their diets than US-born women. Intakes of all nutrients except vitamin C and zinc remained significantly higher in Mexico-born women when nutrients from both diet and vitamin supplements were considered. Among Mexico-born women, increasing years of residence in the US was associated with lower intake of calories (P(trend) < 0.01), fibre (P(trend) < 0.01), folate (P(trend) = 0.03), iron (P(trend) = 0.05) and zinc (P(trend) = 0.03), although only the trend for iron remained significant when vitamin supplement sources were included. A large percentage of women had inadequate intake of vitamin E (58%), folate (61%), iron (77%) and zinc (47%) from their diets during pregnancy and these rates were higher in US-born women than Mexico-born women.