Threatened abortion: A risk factor for poor pregnancy outcome, a population-based screening study.

Objective: The purpose of this study was to determine whether patients with first-trimester threatened abortion are at increased risk for poor pregnancy outcome.

Study Design: A large prospective multicenter database was studied. Subjects were divided into three groups: (1) no bleeding, (2) light bleeding, and (3) heavy bleeding. Univariate and multivariable logistic regression analyses were used.

Results: The study comprised 16,506 patients: 14,160 patients without bleeding, 2094 patients with light bleeding, and 252 patients with heavy bleeding. Patients with vaginal bleeding, light or heavy, were more likely to experience a spontaneous loss before 24 weeks of gestation (odds ratio, 2.5 and 4.2, respectively) and cesarean delivery (odds ratio, 1.1 and 1.4, respectively). Light bleeding subjects were more likely to have preeclampsia (odds ratio, 1.5), preterm delivery (odds ratio, 1.3), and placental abruption (odds ratio, 1.6). Heavy vaginal bleeding subjects were more likely to have intrauterine growth restriction (odds ratio, 2.6), preterm delivery (odds ratio, 3.0), preterm premature rupture of membranes (odds ratio, 3.2), and placental abruption (odds ratio, 3.6).

Conclusion: First-trimester vaginal bleeding is an independent risk factor for adverse obstetric outcome that is directly proportional to the amount of bleeding.