Bleeding during pregnancy is associated with familial preterm birth

the purpose of this study is to identify risk factors for familial, likely genetically-determined, preterm birth.

We performed a case-control study, enrolling 211 patients (103 cases and 108 controls). Cases delivered between 20 and 35 weeks gestation, with a prior preterm birth or first-degree relative born prematurely. Controls delivered between 37-42 weeks. Groups were compared using a comprehensive questionnaire validated by medical record. Multivariate logistic regression assessed risk factor associations.

Of cases, 30% reported bleeding during pregnancy compared with 5% of controls, adjusted odds ratio (adjOR) 9.0, 95%CI 3.31-24.47. Of cases that delivered at 20-28 weeks, 44.8% reported bleeding during pregnancy compared with 24.6% at 29-35 weeks, p = .04. Other associations were prior first-trimester miscarriage adjOR 2.55 (CI 1.21-5.35) or second-trimester miscarriage, adjOR 6.3 (CI 1.76-22.56).

Bleeding during pregnancy and prior miscarriage were significantly associated with familial preterm birth. The magnitude of effect for bleeding in pregnancy was higher with earlier preterm births. These associations warrant further investigation.