Hypertensive disorders of pregnancy: heterogeneity in risk factors and maternal and neonatal outcomes across subtypes-a 6-year retrospective cohort study.

BACKGROUND: Hypertensive disorders of pregnancy (HDP) are major obstetric complications that seriously threaten maternal and neonatal health. Current research predominantly focuses on preeclampsia (PE). However, systematic comparisons across all four HDP subtypes-gestational hypertension (GH), preeclampsia (PE), chronic hypertension (CH), and superimposed preeclampsia (SPE) remain limited, hindering a deeper understanding of their heterogeneous risks and precise management. OBJECTIVE: This study aimed to systematically analyze the epidemiological trends, independent risk factors, and differential impacts on maternal and neonatal outcomes of HDP and its subtypes, based on large-sample clinical data. METHODS: This retrospective cohort study was conducted at a single tertiary care center in southern China, including 20,081 pregnant women who delivered at Guangxi Zhuang Autonomous Region People's Hospital between January 2019 and December 2024. Participants were classified into an HDP group (n = 1,334) and a non-HDP group (n = 18,747) based on discharge diagnoses. The HDP group was further subdivided into GH, PE, CH, and SPE. Baseline characteristics and pregnancy outcomes were collected. Multinomial logistic regression was used to identify factors associated with each HDP subtype vs. non-HDP. Multivariate logistic regression was used to assess associations between HDP subtypes and adverse outcomes, and adjusted models were constructed to assess independent risks. Given the small SPE sample (n = 24), CH and SPE were combined (CH-SPE) for multivariable analyses to ensure model stability. Sensitivity analyses separating CH and SPE were also performed to assess the robustness of findings. RESULTS: From 2019 to 2024, the overall incidence of HDP was 6.6%, with CH incidence increased by 78.2% (from 0.6% to 1.0%), and SPE incidence increased from 0.1% in 2019 to 0.7% in 2024. Multinomial analysis identified advanced maternal age (≥35 years), pre-pregnancy overweight/obesity, elevated fasting blood glucose (FBG), and gestational diabetes mellitus (GDM) as common risk factors for all HDP subtypes. Significant heterogeneity was observed among subtypes: PE demonstrated the strongest association with twin pregnancy (OR=4.071, 95% CI: 2.843--5.828), and elevated serum creatinine (Cr) was a specific risk factor for PE. CH-SPE was significantly associated with assisted reproductive technology (ART) (OR=2.032, 95% CI: 2.278--3.230), while higher education level was a unique protective factor (Postgraduate vs. Junior high school or below: OR=0.413, 95% CI: 0.259--0.660). All HDP subtypes significantly increased the risks of cesarean delivery with CH-SPE group (adjusted OR=3.399, 95% CI: 2.408--4.798) having the highest risk. Adverse neonatal outcomes (LBW and SGA) were predominantly concentrated in the PE and CH-SPE subtypes. CONCLUSION: Significant heterogeneity exists in risk factors and maternal-neonatal outcomes across different HDP subtypes. This study highlights the rapidly increasing incidence and unique risk profiles of chronic hypertension-based subtypes, emphasizing the urgency for precise screening and management pre-pregnancy and during early gestation. The findings provide important evidence for subtype-stratified risk assessment and individualized clinical intervention in HDP.