Objective: To evaluate the association of first-trimester bleeding without miscarriage and complications later in the first pregnancy as well as in the next pregnancy.
Methods: In a retrospective, registry-based cohort study, we identified women delivering in Denmark from 1978 to 2007 with a first singleton pregnancy (n=782,287) and first and second singleton pregnancies (n=536,419). First-trimester bleeding is defined as vaginal bleeding before 12 full weeks of gestation. We employed multivariate logistic regression with adjustment for maternal age and calendar year.
Results: First-trimester bleeding increased the risk of delivery in weeks 32-36 from 3.6% to 6.1% (odds ratio [OR], 1.65; 95% confidence interval [CI], 1.57-1.77) and in weeks 28-31 from 0.3% to 0.9% (OR 2.98; 95% CI 2.50-3.54) and increased the risk of placental abruption from 1.0% to 1.4% (OR 1.48; 95% CI 1.30-1.68). First-trimester bleeding in the first pregnancy increased the risk of recurrence in the second pregnancy from 2.2% to 8.2% (OR 4.05; 95% CI 3.78-4.34), preterm delivery from 2.7% to 4.8% (OR 1.83; 95% CI 1.67-2.00), and placental abruption from 0.9% to 1.0% (OR 1.29; 95% CI 1.07-1.56) in the second pregnancy.
Conclusion: Women with first-trimester bleeding in the first pregnancy have an increased risk of complications later in the first pregnancy and of recurrence of first-trimester bleeding and other complications in the second pregnancy.