Hemoglobin (HB) and ferritin levels were measured in 568 pregnant women living in a peri-urban community of Lima Peru, and participating in a randomized, double-blind prenatal supplementation study. At entry into prenatal care, 10-24 wks gestation, women were randomly assigned to two groups (A and B): one received 60 mg iron (as ferrous sulphate) and 250 ug folate per day, the other group received the same amount of iron and folate with 15 mg zinc (as zinc sulphate). Biochemical assessments were made at enrollment, 28-30 wks, 37-38 wks, and in the neonate. HB (g/L) Group 10-24 wks 28-30 wks 37-38 wks Neonate A 11.48 ± 13.8 109.8 ± 12.7 115.3 ± 13.6 177.4 ± 22.3 B 115.6 ± 12.7 110.5 ± 12.6 114.1 ± 13.0 175.0 ± 21.6 Analysis-of-variance for a randomized block design was used to evaluate changes in HB by supplementation group at each time point. Non-parametric tests were done for ferritin analysis. HB changes across time points in pregnancy were statistically significant (P < 0.05) but no differences were found between supplementation groups at any time point. HB levels in the neonates were in the normal ranges, and did not differ depending on the type of maternal supplement consumed. These data provide evidence that inclusion of zinc in prenatal iron supplements did not adversely affect maternal hematologic status in these women.