Characteristics and fetal outcomes of pregnant women with hypertensive disorders in China: a 9-year national hospital-based cohort study

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Hypertensive disorders of pregnancy (HDP) are a growing concern and a challenge for maternity care providers as the prevalence of hypertension continues to increase. However, optimal management of HDP is unclear. Therefore, we aimed to explore the differences in adverse fetal outcomes among women with different subtypes of HDP and different blood pressure (BP) levels, to provide evidence-based management of HDP. We obtained data from China's National Maternal Near-Miss Surveillance System from 2012 to 2020. Associations between BP management and adverse fetal outcomes, stratified by the four subtypes of HDP, were assessed using logistic regression analysis with a robust variance estimator. For the period, a total of 393,353 pregnant women with HDP were included in the study; 8.51% had chronic hypertension, 2.27% had superimposed preeclampsia, 50.17% had preeclampsia or eclampsia, and 39.04% had gestational hypertension. The BP levels at delivery admission were mostly (61.14%) of non-severe stage 2 (systolic BP 140-159mm Hg and/or diastolic BP 90-109mm Hg) hypertension by American Heart Association classification. A high rate of adverse fetal outcomes was observed among women with HDP, especially among those aged < 20 or > 35 y or those diagnosed with superimposed preeclampsia. Compared with those with normal BP levels at delivery admission, we found an upward curve with increased risk among pregnant women with more severe BP levels, including the risk of preterm birth and small for gestational age (SGA) fetus. The odds ratios (ORs) of stillbirth, neonatal death, and low Apgar scores associated with severe stage 2 hypertension increased significantly. In addition, the association between BP at admission and fetal outcomes differed among women with varying HDP subtypes. Pregnant women with preeclampsia or eclampsia had an increased risk for preterm birth (adjusted OR [aOR], 1.33 [95% confidence interval {CI}, 1.07 ~ 1.65]) and SGA (aOR, 1.37 [95% CI, 1.10 ~ 1.71]) even when the admission BP was at stage 1 level. Greater attention should be paid to cases involving preeclampsia superimposed on chronic hypertension and pregnant women aged < 20 or > 35 y to mitigate the burden of adverse fetal outcomes caused by HDP.