Assessing the Clinical Significance of Third-Trimester Post-Coital Bleeding

Introduction: This study aimed to evaluate the impact of third-trimester post-coital bleeding (PCB) on pregnancy outcomes. Methods: A retrospective cohort study was conducted at two tertiary medical centers, including all pregnant women between 24 and 34 weeks of gestation referred due to vaginal bleeding over an 11-year period. The study population includes all singleton deliveries; within this population, women were further classified into three groups: those admitted due to vaginal bleeding related to PCB, those admitted due to vaginal bleeding not related to PCB, and those who did not report vaginal bleeding. The primary outcome measure was delivery prior to 37 weeks of gestation, while secondary outcome measures included maternal and neonatal complications. Baseline characteristics of the two groups were compared. Results: During the study period, there were a total of 51,698 deliveries. Among these, 230 cases involved bleeding between 24 and 34 weeks of gestation, 34 (14.8%) were identified as PCB, and 196 as bleeding unrelated to intercourse. In addition, 51,468 pregnancies without bleeding were analyzed as the general population for comparison. The incidence of preterm labor before 37 weeks of gestation was notably higher in both women with PCB (14.7%) and those with bleeding unrelated to coitus (20.9%) compared to the general population (5.6%); however, there was no statistically significant difference between the two bleeding groups (p = 0.403) while both were significantly different from the general population (p < 0.001). The odds ratio for preterm birth before 37 weeks of gestation after PCB was 3.29 (95% CI: 1.26-8.56, p = 0.0149). There were no significant differences between the PCB and bleeding unrelated to intercourse groups in terms of maternal and neonatal complications. Conclusion: This study found that third-trimester PCB is a risk factor for preterm delivery, with rates similar to other causes of third-trimester bleeding but significantly higher than the general population without bleeding. These findings challenge the assumption that PCB is benign.