Mean maternal second-trimester hemoglobin concentration and outcome of pregnancy: a population-based study.

Both anemia and the lack of physiological maternal plasma volume expansion during the second trimester are associated with higher maternal morbidity and poor fetal outcome. Mean hemoglobin levels between the 14th and 30th gestational weeks were calculated in 4985 consecutive pregnant women and were correlated with outcome data of pregnancy. It was found that 9.4% of participants (n=3959) had normal pregnancy outcome. Mean maternal hemoglobin levels were significantly lower in women with a normal pregnancy (11.96+/-0.94 g/dL) compared with women who had adverse outcome events (preeclampsia, n=423, 12.5 +/- 1.0 g/dL, P< .0001; early birth, n=464, 12.2+/-1.01 g/dL, P< .0001; low birth weight newborn, n=473, 12.2+/-1.10 g/dL, P< .0001; intrauterine growth retardation, n=250, 12.2+/-1.0 g/dL, P< .0001). The risk for any adverse outcome event was lowest with a mean hemoglobin between 11.0 and 12.0 g/dL (odds ratio, 0.625; 95% confidence interval, 0.43-0.89) and highest between 13.0 and 15.0 g/dL (odds ratio, 2.24; 95% confidence interval, 1.54-3.31). In this population-based study from a community in Western Germany, impaired plasma volume expansion was an independent risk factor for the development of an adverse outcome of pregnancy.