High Hemoglobin Level is a Risk Factor for Maternal and Fetal Outcomes of Pregnancy in Chinese Women: A Retrospective Cohort Study

Background: To examine the association of hemoglobin (Hb) levels during gestation with the risk of selected adverse pregnancy outcomes in Chinese women. Methods A total of 1911 singleton mothers were included. Hb levels were measured during the second (16-18th weeks) and third (28-30th weeks) trimesters of pregnancy, and pregnancy outcomes were followed. Statistical analysis was performed using multivariate logistic regression. Results After multivariable adjustment, Hb levels > 130 g/L in the second trimester increased the risk of low-birth-weight infants (LBW) (odds ratio [OR], 2.54; 95% confidence interval [CI], 1.12–5.77). In the third trimester of gestation, compared with women whose Hb levels between 110–119 g/L, women with Hb levels > 130 g/L had an increased risk of LBW (OR, 2.17; 95% CI, 1.05–4.48) and small-for-gestational-age infants (SGA) (OR, 1.98; 95% CI, 1.04–3.78). In addition, maternal Hb levels of  130 g/L at the second week that were restored vs not restored in the third trimester decreased the risk of preterm birth (PTB) by 80% (95% CI, 0.07–0.58) and 86% (95% CI, 0.03–0.84), respectively. Conclusion Maternal Hb > 130 g/L was associated with increased risk of adverse pregnancy outcomes. Reduction of PTB risk was observed with correction of Hb level during the third trimester.