Apoptosis in the chorion of fetal membranes in preterm premature rupture of membranes

We sought to determine if apoptosis in the chorion of fetal membranes was increased in patients with preterm premature rupture of membranes (PPROM) with histological chorioamnionitis. Using the TUNEL (terminal uridine deoxynucleotidyl transferase dUTP nick-end labeling) method (ApopTag Plus kit; Oncor, Gaithersburg, MD), apoptosis was quantified. Of the 47 subjects with PPROM, 18 lacked sufficient chorion for quantification (confirmed by cytokeratin staining). In the remaining 30 subjects, fetal membranes with and without chorioamnionitis were examined and apoptosis was quantified. There were no differences in maternal age, race, insurance, cesarean rate, or gestational age between groups. The chorion of fetal membranes from PPROM patients with chorioamnionitis had significantly more apoptotic nuclei than those without chorioamnionitis (19.1 versus 0.8; p=.005). Of the 17 subjects excluded for absence of chorion, 16 (94%) had at least moderate chorioamnionitis. This investigation suggests that apoptosis is accelerated in the chorion of PPROM subjects with chorioamnionitis. Absence of the chorion in 37% of subjects is supportive of the hypothesis that inflammation accelerates cell death and destruction of the chorion.