Background
The management of antepartum haemorrhage of unknown origin (APHUO) remote from term remains controversial.

Aim
To determine the rate and risk factors in predicting preterm delivery among women presenting with APHUO before 34 weeks of gestation.

Methods
All singleton pregnancies with the first episode of APHUO before 34 weeks of gestation who delivered between January 1995 and December 2004 were reviewed. The predictability of risk factors was assessed by both univariate and multivariate analysis. The cumulative rates of preterm delivery prior to 34 weeks were compared by using the Kaplan–Meier survival analysis and log‐rank test between those with and those without risk factors.

Results
The rates of preterm delivery prior to 34 and 37 weeks of gestation were 7.3 and 17%, respectively. Uterine contractions, persistent bleeding, two or more episodes of APHUO and a history of spontaneous preterm deliveries were significant risk factors for preterm birth prior to 34 weeks in a multivariate logistic regression. Women with one risk factor had a hazard ratio of 5.5 (95% CI: 3.2–9.6) in having preterm delivery prior to 34 weeks compared with those without risk factors, whereas women with any two risk factors had a hazard ratio of 5.2 (95% CI: 2.1–12.9) compared with those with one risk factor.

Conclusions
APHUO prior to 34 weeks of gestation is associated with three to fivefold increased risk of preterm delivery. Identification of several risk factors could further help to predict early preterm delivery and appropriate triage management.