Low-dose aspirin in the prevention of pre-eclampsia in China: postpartum hemorrhage in subgroups of women according to their characteristics and potential bleeding risk

Background: The APPEC study is a large-population randomized controlled trial in China evaluating the role of low-dose aspirin prophylactic treatment for pre-eclampsia. There was no statistically significant difference in postpartum hemorrhage (PPH) incidence between the aspirin and control groups. This study aimed to evaluate the potential bleeding risk of 100 mg aspirin in high-risk pregnant women and the difference in the incidence of PPH according to maternal characteristics. Methods: This is a secondary data analysis of the APPEC study. Platelet counts and coagulation test results were collected at five follow-up visits. Subgroups defined by maternal age (<35 years and >= 35 years), pre-pregnancy body mass index (pre-BMI, <28 kg/m(2) and >= 28 kg/m(2)), parity, gestational age at enrollment, and medical history, including pre-eclampsia, chronic hypertension, and diabetes mellitus, were analyzed. Logistic regression analysis was used to determine the statistical significance of the difference in the incidence of PPH after aspirin administration in pregnant women in each subgroup. Adjustment using multiple logistic regression models followed these analyses. Binary logistic regression was used to determine the relationship between pre- BMI and PPH. Results: There was no significant difference between the aspirin and control groups in bleeding risk (3.4% [16/464] vs. 3.0% [13/434], T = 0.147, P = 0.701). No significant difference was found in the incidence of PPH in total (relative risk = 1.220, 95% confidence interval [CI] = 0.720-2.067, P = 0.459; aspirin group vs. control group, 6.5% [30/464] vs. 5.3% [23/434], P = 0.459) or in subgroup analysis. A significant correlation between pre-BMI and PPH was found in the aspirin group, while in the control group there was no significant correlation (aspirin group, odds ratio [OR] = 1.086, 95% CI = 1.004-1.175, P = 0.040; control group, OR = 1.060, 95% CI = 0.968-1.161, P = 0.209). Conclusions: A dosage of 100 mg of aspirin per day, initiated from 12 to 20 gestational weeks until 34 weeks of gestation, did not increase the risk of potential bleeding and PPH regardless of the maternal characteristic. In the aspirin group, the positive correlation between BMI and PPH was significant. Trial Registration: ClinicalTrials.gov, NCT01979627.