High and low hemoglobin levels during pregnancy: differential risks for preterm birth and small for gestational age
Section snippets
Materials and methods
Data for this study were obtained from publicly funded maternal child health program clinic records submitted to the CDC Pregnancy Nutrition Surveillance System between 1990 and 1993. Ninety-six percent of the records were from women attending the Special Supplemental Nutrition Program for Women, Infants, and Children. We included all surveillance records on singleton pregnant women from 11 states in the United States who entered the maternal child health program between 1 and 36 weeks’
Results
Table 3 shows maternal and infant characteristics by trimester of entry into the maternal-child health program, the trimester during which maternal hemoglobin level was measured. Because of the large sample size in each group, even small differences were statistically significant. Thus, the magnitude of the relative differences rather than their statistical significance was examined. Relative differences of more than 25% were considered noteworthy.
Women who entered the maternal-child health
Discussion
We found that maternal anemia during pregnancy was associated with preterm birth but not with delivery of an SGA infant. Moreover, high maternal hemoglobin level was associated with SGA but not with preterm birth. We observed the strongest increased risk of preterm birth among women with more severe anemia (hemoglobin Z score less than −3.0), which corresponds to an approximate hemoglobin level less than 90 g/L to 100 g/L, depending on week of gestation (Table 2). The strongest risk of SGA was
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