A randomized comparison of routine versus selective iron supplementation during pregnancy.

This trial compares routine and selective iron supplementation during pregnancy to determine whether routine supplementation adversely affects fetal growth, increases infections and subjective adverse effects, and/or delays birth. At their first prenatal visit, 2912 pregnant women were randomized into two groups (2694 gave birth). Compliance was satisfactory as measured by self-reports by mothers and hematocrit values in the third trimester. More women in the routinely supplemented group had subjected adverse effects. The groups were similar in regard to most of the other outcomes. In the selectively supplemented group, there was weak evidence for increase in sick-days, referrals to hospital outpatient clinic, cesarean section, blood transfusions, and infants who were diagnosed as having hyperviscosity. In the routine group, there were somewhat more women with gestations greater than or equal to 41 weeks and more dead infants. The subgroup analyses suggest that some of the apparently worse outcomes in the selective group were due to reactions of midwives and physicians to low hematocrit values.