Anemia before pregnancy and risk of preterm birth, low birth weight and small-for-gestational-age birth in Korean women.

BACKGROUND/OBJECTIVES: Maternal prepregnancy hemoglobin concentration has rarely been explored as a risk of poor birth outcomes. This study examined whether women with anemia before pregnancy would be at higher risk of preterm birth, low birth weight (LBW) and small-for-gestational-age (SGA) birth.

SUBJECTS/METHODS: This retrospective cohort study was conducted on 70,895 Korean women who delivered a singleton in 1999, with their prepregnancy hemoglobin concentration measured at health examinations in 1997-1999. A logistic model was used to adjust for confounding variables and calculate odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

In adjusted analysis, moderate-to-severe anemia (hemoglobin <100 g/l) before pregnancy was associated with preterm birth (OR, 1.53; 95% CI, 1.05-2.23; P=0.027), LBW (OR, 1.81; 95% CI, 1.24-2.64; P=0.002) and SGA (OR, 1.71; 95% CI, 1.35-2.17; P<0.001) when compared with prepregnancy hemoglobin of 120-149 g/l. Mild anemia (hemoglobin of 100-119 g/l) was also associated with LBW (OR, 1.21; 95% CI, 1.06-1.39; P=0.005) and SGA (OR, 1.15; 95% CI, 1.06-1.25; P=0.001). The risk of preterm birth, LBW and SGA across 11 prepregnancy hemoglobin groups depended on the severity of anemia (P for trend=0.042, 0.019, and 0.001, respectively). A high hemoglobin concentration (≥150 g/l), however, was not associated with adverse birth outcomes.

CONCLUSIONS

Anemia, not high hemoglobin concentration, before pregnancy was associated with an elevated risk of preterm birth, LBW and SGA, and the risk increased with the severity of anemia in Korean women.