Objective: Our aim was to find out whether patients delivered preterm because of preterm labor or preterm premature rupture of membranes can be categorized according to clinical characteristics and placental pathologic findings.
Study design: We performed a case-control study of 105 patients who were delivered preterm, 42 because of preterm labor and 63 because of premature rupture of membranes, and 105 patients who were delivered at term after uncomplicated pregnancies.
Results: Maternal placental vascular lesions were present in 14 (34.1%) patients with preterm labor, 19 (35.1%) patients with premature rupture of membranes, and 9 (11.8%) control patients (odds ratios 3.8 and 4.0, 95% confidence intervals 1.3 to 11.1 and 1.5 to 10.8, p = 0.0065 and 0.0022, respectively). Infection of the products of conception was found in 16 patients (38%) with preterm labor, 23 patients (36.5%) with premature rupture of membranes, and 19 control patients (18%) (odds ratios 2.7 and 2.6, 95% confidence intervals 1.1 to 6.6 and 1.2 to 5.6, p = 0.017 and 0.01, respectively). Patients with maternal placental vasculopathy had significantly different characteristics compared with those of infected patients.
Conclusions: It is possible to identify two subgroups of patients among those who are delivered preterm because of preterm labor or premature rupture of membranes, one with infection of the products of conception and another with maternal placental vasculopathy.