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First-Trimester Bleeding and the Risk of Pregnancy Loss in a Prospective Cohort

Alexandra C Sundermann1, Elizabeth A Jasper, Paulina E Chumakov

  • 1Division of Quantitative and Clinical Sciences, Department of Obstetrics and Gynecology, Institute for Medicine and Public Health, and the Department of Biomedical Informatics, Vanderbilt University Medical Center, and the Vanderbilt University School of Medicine, Nashville, Tennessee; and the Department of Obstetrics and Gynecology, University of Kentucky, Lexington, Kentucky.

Obstetrics and Gynecology
|February 19, 2026
PubMed

Vaginal bleeding in the first trimester is common, but our understanding of how bleeding relates to the risk of pregnancy loss is limited. In a prospective cohort study, participants provided information on bleeding episodes during early pregnancy and underwent a first-trimester research ultrasonogram. Among 5,425 participants, 25.0% of participants reported first-trimester bleeding, and 12.0% of pregnancies ended in loss. Bleeding was not associated with risk of pregnancy loss (hazard ratio [HR] 0.89, 95% CI, 0.75-1.07). First-trimester bleeding coupled with ultrasound measurements that lagged more than 5 days behind last menstrual period (LMP) dating was associated with increased risk (HR 2.72, 95% CI, 2.10-3.53). These findings indicate that reassurance is appropriate for most patients experiencing first-trimester bleeding when ultrasound measurements align with LMP.

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