[Association between pregnancy-induced hypertension, cesarean delivery and perinatal mortality: a prospective study]

To examine the relationship between pregnancy-induced hypertension (PIH) and risks of perinatal mortality.

A population-based, retrospective cohort study was conducted based on 134 858 women registered in a perinatal health care surveillance system and delivered singleton births between 1995 to 2000 in Zhejiang province, China. Multivariate logistic regression models were employed to estimate the relative risk (OR) and 95%CI.

The perinatal mortality rate (95%CI) was 7.6 per thousand (7.1 - 8.1) in normotensive women and 9.2 per thousand (7.7 - 10.8) in PIH women. The cesarean delivery rate was 45.7% in normotensive women and 55.7% in groups with PIH. When compared with the normotensive women, the unadjusted OR (95%CI) for perinatal mortality was 1.21(1.01 - 1.46) in groups with PIH; 0.97 (0.77 - 1.22) in groups with mild PIH, 1.73 (1.26 - 2.37) in groups with moderate PIH, and 2.01 (1.18 - 3.43) in groups with severe PIH; 0.99 (0.77 - 1.26) in groups with PIH developed before delivery, 1.39 (1.05 - 1.84) in groups with PIH developed in second trimester, and 2.69 (1.54 - 4.69) in groups with PIH developed in third trimester. After controlling for maternal age, occupation, educational attainment, parity, times of prenatal visit, infant's sex, pregnancy complications and cesarean delivery, the OR (95%CI) for perinatal mortality was 1.09 (0.90 - 1.31) in women with PIH when compared with the normotensive groups. The adjusted OR for perinatal mortality was 0.81 (0.64 - 1.02) in groups with mild PIH, 1.94 (1.41 - 2.67) in groups with moderate PIH, and 3.32 (1.92 - 5.75) in groups with severe PIH; 0.82 (0.63 - 1.05) in groups with PIH developed before delivery, 1.51 (1.14 - 2.00) in groups with PIH in second trimester, and 2.67 (1.52 - 4.70) in groups with PIH in third trimester.

Moderate and severe PIH early developed during pregnancy could increase the risk of perinatal mortality, while cesarean delivery could decrease the risks in women with PIH.