Objective To examine the association between second-trimester hemoglobin (Hb) concentration and the risk of pregnancy-induced hypertension syndrome (PIH) in a Chinese population. Methods Subjects were women who delivered a singleton baby in four cities or counties in Jiangsu Province and Zhejiang Province, China, during the period of 1995-2000. Hb concentration was the lowest coneentra-tion measured in the second trimester. A total of 95 620 women were included. PIH was diagnosed according to the criteria proposed by the Second Conference of the Task Force on the Prevention and Care of Pregnancy-induced Hypertension, held in 1983 in Shanghai, China. Incidence of PIH was calculated and compared be-tween groups of women with different concentrations of second-trimester Hb. Multlple logistic regression was used to address the relationship between second-trimester Hb concentration and the risk of PIH while control-ling for age, occupation, education, parity and BMI. Results The overall PIH incidence was 8. 0 %. Women with second-trimester Hb concentrations of 100-109 g/L had lowest PIH incidence. The incidence increased with either increasing or decreasing hemoglobin concentrations. Compared with women with Hb concentrations of 100-109 g/L, women with lib concentrations of lower than 80 g/L had 79 % higher risk (OR = 1.79, 95 % CI: 1.29 - 2. 49), and women with Hb concentration of 150 g/L or higher had 47% higher risk (OR=1.47, 95 %CI: 1.00-2.21) of PIH. Condusion A U-shaped relationship is present between second-trimester Hb concentration and the risk of PIH. Severe anemia as well as high Hb concentration is associated with an increased risk of PIH.
