Prevalence, Risk Factors, and Maternal–Fetal Outcomes of First Trimester Vaginal Bleeding

Abstract

Background: First-trimester vaginal bleeding (FTVB) is a common but clinically significant event, with prevalence estimates ranging from 7% to 25%. While many episodes are self-limiting, FTVB is associated with an increased risk of adverse outcomes, including miscarriage, preterm birth, and placental complications. This study aimed to determine the local prevalence, identify risk factors, and quantify maternal-fetal outcomes associated with FTVB in a tertiary care setting.

Methods: A retrospective cohort study was conducted using medical records of 615 pregnant women who registered for antenatal care at ≤13⁺⁶ weeks at a tertiary hospital. Women with documented FTVB (n=102) were compared to those without (n=513). Data on demographics, obstetric history, sonographic findings, and pregnancy outcomes were extracted. Multivariable logistic regression identified independent risk factors for FTVB and its associated adverse outcomes. A predictive model for a composite adverse outcome (early loss, preterm birth, or NICU admission) among women with bleeding was developed.

Results: The prevalence of FTVB was 16.6% (95% CI: 13.8–19.8%). Independent risk factors included a history of prior miscarriage (aOR=1.85, 95% CI: 1.15–2.97), prior bleeding episodes (aOR=2.78, 95% CI: 1.49–5.19), subchorionic hematoma on ultrasound (aOR=6.24, 95% CI: 3.86–10.08), maternal age ≥30 years (aOR=1.92, 95% CI: 1.20–3.08), and booking hemoglobin <11 g/dL (aOR=1.79, 95% CI: 1.12–2.85). FTVB was significantly associated with early pregnancy loss (aOR=3.41, 95% CI: 1.71–6.78), preterm birth (aOR=1.89, 95% CI: 1.05–3.41), placental abruption (aOR=3.25, 95% CI: 1.18–8.96), lower mean birth weight (-148 g, p<0.05), and NICU admission (aOR=1.81, 95% CI: 1.05–3.13). A prediction model for adverse outcomes in the bleeding group had an AUC of 0.72.

Conclusion: FTVB is a prevalent finding that serves as a marker for heightened risk throughout pregnancy. It is strongly associated with a history of miscarriage, sonographic findings of subchorionic hematoma, and maternal anemia. Critically, FTVB significantly increases the odds of adverse outcomes from the first trimester through delivery, underscoring the need for vigilant antenatal surveillance in these pregnancies.