What is the clinical evidence from this study?

Study design: Cohort. Population: Chronic hypertension in pregnancy (n=367). Intervention: Aspirin vs. Control (no aspirin). Primary outcome: Incidence of superimposed preeclampsia (OR 0.87, 95% CI 0.49-1.54, p=0.64).

January 9, 2026BMC Pregnancy and Childbirth1 citationsOpen Access

The effectiveness of 100 mg aspirin in preventing superimposed preeclampsia in women with chronic hypertension: a real-world study

YQYanli QiaoNanjing Drum Tower Hospital YCYechao ChenChina Pharmaceutical University YCYawen ChenNanjing Drum Tower Hospital

Key Result

Initiating 100 mg/day of aspirin between 12 and 20 weeks of gestation did not significantly reduce the incidence of superimposed preeclampsia in women with chronic hypertension (OR 0.87).

Study Design

Type

Cohort (n=367)

Multicenter

Structured PICO

Does aspirin 100 mg/day prevent superimposed preeclampsia in pregnant women with chronic hypertension?

Population

367 pregnant women with chronic hypertension (CHTN) who began prenatal care before 20 weeks of gestation and delivered a singleton

Intervention

Aspirin 100 mg/day initiated between 12 and 20 weeks of gestation

Comparator

Control group (no aspirin)

Outcome

Incidence of superimposed preeclampsiahard clinical

In pregnant women with chronic hypertension, 100 mg/day aspirin initiated between 12 and 20 weeks of gestation did not reduce superimposed preeclampsia but significantly reduced the risk of small for gestational age infants.

Main Result

Effect estimate: OR 0.87 (95% CI 0.49-1.54)

Absolute Event Rate: 34.6% vs 37.7%

p-value: p=0.64

Limitations

Differences in baseline characteristics prior to adjustment may reflect a higher baseline risk profile and contribute to residual confounding.
Suboptimal pregnancy management, including insufficient calcium supplementation and inconsistent blood pressure control, may have limited aspirin effectiveness.
Biomarkers commonly used in first-trimester preeclampsia prediction models (PlGF, sFlt-1) were not included.
Retrospective single-center cohort study design does not allow for causal inference.
Sample size may have been insufficient to detect significant differences in the primary outcome.
The 100 mg daily dosage of aspirin may still be suboptimal for this specific population.
Patient adherence was based on prescription information or self-reports, which may not accurately reflect actual compliance.

Abstract

OBJECTIVE: This study aims to evaluate the real-world effectiveness of 100 mg aspirin in preventing superimposed preeclampsia (PE) in pregnant women with chronic hypertension (CHTN). STUDY DESIGN: This retrospective cohort study included pregnant women with CHTN who began prenatal care before 20 weeks of gestation and delivered a singleton at Nanjing Drum Tower Hospital, affiliated with Nanjing University Medical School. The deliveries occurred between January 1, 2018, and May 1, 2025. The primary exposure was 100 mg/day aspirin initiated between 12 and 20 weeks of gestation, and the primary outcome was the incidence of superimposed PE. Secondary outcomes included PE delivery before 34 weeks, PE delivery before 37 weeks, preterm birth, postpartum hemorrhage, gestational diabetes mellitus, small for gestational age (SGA), and a composite of adverse neonatal outcomes. Multivariable logistic regression and inverse probability of treatment weighting (IPTW) were used to adjust for confounding factors. RESULTS: During the study period, 367 women met the inclusion criteria, with 111 in the aspirin group and 256 in the control group. After IPTW adjustment, baseline characteristics were comparable between the two groups. The incidence of superimposed PE was 34.6% in the aspirin group and 37.7% in the control group, with no statistically significant difference (weighted OR = 0.87, 95% CI: 0.49-1.54; p >0.05). In secondary outcomes, the incidence of SGA was significantly lower in the aspirin group both before and after IPTW adjustment (p0.05). Additionally, subgroup analyses showed no significant heterogeneity in aspirin effect when stratified by aspirin-related factors (initiation timing, adherence, and concurrent calcium supplementation) or CHTN-related factors (timing of diagnosis, blood pressure levels before 20 weeks of gestation, and use of antihypertensive medication within three months prior to conception or before 20 weeks) (p >0.05). CONCLUSION: Our study suggests that initiating 100 mg/day of aspirin between 12 and 20 weeks of gestation does not significantly reduce superimposed PE in women with CHTN; however, it significantly reduces the risk of SGA. Subgroup analyses also indicated that even initiation before 16 weeks did not provide additional preventive effect against PE.

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