The objective of this article is to assess changes in diet composition, defined in terms of macronutrient intake and types of foods consumed, in pregnancy in poor urban women in Colombia. The subjects were 20 pregnant and 20 matched nonpregnant, nonlactating (NPNL) women 19 to 35 years of age. The pregnant women were studied in three measurement rounds at 14.0 +/- 3.6, 27 +/- 2.2, and 35 +/- 1.7 weeks gestation, and the NPNL women in three measurement rounds approximately 3 months apart. Dietary intake was obtained from estimated food records and macronutrient composition from published sources. Types of foods consumed were aggregated into 16 groups: alcohol; breads; candy; coffee, chocolate; juices; fruit; legumes; meat, fish, offal; dairy; vegetable dishes; other; rice, pasta; tubers, plantains; salads; soft drinks; and soups. Macronutrient intakes showed nonsignificant increases in pregnancy. There were no significant differences between pregnant and NPNL women, except for carbohydrate intake in late pregnancy (P = 0.03). Carbohydrate, fat, and protein provided 74%, 17%, and 12% of dietary energy, respectively, in pregnant women at baseline, and did not change significantly. Except for a decrease in fruits, the types of foods consumed did not change significantly in pregnancy. There were no between-group differences in types of foods consumed except for the greater number of fruits consumed by pregnant women at baseline (P = 0.004). We conclude that in this population there were no changes in diet composition in pregnancy, except for an increase in fruit consumption in Round 1. Am. J. Hum. Biol. 11:753-762, 1999. Copyright 1999 Wiley-Liss, Inc.