Comment on “First-Trimester Bleeding and the Risk of Pregnancy Loss in a Prospective Cohort”

First-trimester bleeding is common and occurs in approximately one in four pregnancies. It is distressing for patients with a desired pregnancy, which often leads to a need for counseling from their care team. However, research on whether bleeding indicates an increased risk of pregnancy loss remains limited. This study evaluated the association between first-trimester bleeding, ultrasound findings, and pregnancy loss in a prospective cohort. The authors hypothesized that bleeding combined with delayed fetal growth would be associated with the highest risk of loss.

This prospective cohort study used data from Right From the Start, which recruited participants across North Carolina, Tennessee, and Texas between 2000 and 2012. Patients were enrolled early in pregnancy, at which time they completed a baseline interview and received a standardized first-trimester ultrasound. At the end of the first trimester, participants reported bleeding episodes, timing, heaviness, and pain. Episodes ending within 4 days of pregnancy loss were excluded to distinguish bleeding from the loss itself. Gestational age was based on self-reported last menstrual period (LMP) dating. The outcome was the hazard ratio of pregnancy loss when first-trimester bleeding occurred, including whether risk changed when episodes were heavy or painful, or if ultrasound measurements lagged behind LMP dating by more than 5 days.

Among 5425 included participants, 25.0% reported bleeding and 12.0% experienced pregnancy loss. Of those with bleeding, 6.3% described it as heavy and 29.0% as painful. Bleeding alone was not significantly associated with loss (HR: 0.89, 95% CI: 0.75-1.07), nor was painful bleeding (HR: 1.19, 95% CI: 0.90-1.56). Among patients with ultrasound growth data, 23.2% had measurements that lagged LMP dating by >5 days. Bleeding was not associated with the presence of this lag, but bleeding combined with the lag was associated with a greater risk of loss (HR: 2.72, 95% CI: 2.10-3.53).

The results show that first-trimester bleeding was not independently associated with pregnancy loss, even when heavy or painful. Increased risk of loss was seen when both bleeding occurred, and ultrasound measurements lagged menstrual dating. This is congruent with previous research, which found that bleeding alone is not a strong predictor of pregnancy loss. Study strengths include community-based recruitment, early enrollment, and standardized ultrasound assessment. Limitations include a higher proportion of planned pregnancies than the general population, possible recall bias, and reliance on LMP dating, which can be inaccurate.

(Summarized from Sundermann AC, Jasper EA, Chumakov PE, et al First-trimester bleeding and the risk of pregnancy loss in a prospective cohort. Obstet Gynecol. 2026;00:1–4. doi:10.1097/AOG.0000000000006202).