Anemia and iron-deficiency anemia: compilation of data on pregnancy outcome.

Anemia diagnosed early in pregnancy is associated with increased risks of low birth weight and preterm delivery. In several studies, the association between anemia and outcomes reversed direction during the third trimester; maternal anemia was no longer a risk factor for poor pregnancy outcomes. Camden study data were used to examine the probable cause of this observation. Maternal iron-deficiency anemia, diagnosed at entry to prenatal care, was associated with low dietary energy and iron, inadequate gestational gain, and twofold or greater increases in the risks of preterm delivery and low birth weight. During the third trimester, these associations (except with inadequate gestational gain) were no longer present. This reversal of risk status may be attributable to the poor predictive value of anemia and iron deficiency tests during the third trimester. However, the relationship between poor diet (with inadequate iron intake) and increased likelihood of preterm delivery persisted during the third trimester.