Prevalence, trends, and subtype-specific outcomes of hypertensive disorders in pregnancy in China: data from 18 million pregnant women in a hospitalization-based retrospective study.

Evidence on subtype-specific risks of adverse outcomes associated with hypertensive disorders of pregnancy (HDP) remains limited. This study aimed to analyze temporal trends in HDP prevalence and investigate subtype-specific associations with maternal and fetal complications. A retrospective cohort study was conducted using data from 1508 maternity hospitals across mainland China from 2016 to 2019, involving 18,916,671 pregnant individuals aged 15-49 years. Poisson regression models were used to estimate adjusted relative risks (aRRs) for outcomes including maternal morbidity, in-hospital mortality, and fetal complications. The prevalence of HDP increased from 4.92 to 6.48% (P < 0.001). The incidence of superimposed preeclampsia almost tripled, rising from 0.11 to 0.32%. In-hospital maternal mortality associated with HDP decreased from 40.26/100,000 to 16.26/100,000, while HDP-related organ dysfunction, such as heart failure and renal failure, increased from 0.78 to 1.02% and from 0.17 to 0.25%, respectively. Examining subtype-specific outcomes, women with preeclampsia with severe features faced the highest risk for heart failure (aRR 3.01; 95% CI, 2.91-3.10), whereas those with superimposed preeclampsia were more susceptible to renal failure (aRR 28.85; 95% CI, 24.70-33.70). Regarding fetal outcomes, superimposed preeclampsia was associated with the highest risks of preterm birth (aRR 4.85; 95% CI, 4.76-4.94) and stillbirth (aRR 5.09; 95% CI, 4.84-5.35). The prevalence of HDP and its related organ dysfunction increased during the study period. The findings underscore the critical need to address HDP-associated organ injury and to develop tailored management strategies for different HDP subtypes.