Objective: Our purpose was to determine the maternal and fetal polymorphonuclear contributions to preterm histologic chorioamnionitis and whether this response differs in clinical chorioamnionitis when compared to cases without clinical chorioamnionitis.
Methods: Paraffin placenta blocks from 19 preterm deliveries with histologic chorioamnionitis, 9 with clinical chorioamnionitis and 10 without clinical chorioamnionitis, were identified. Only placentas from male fetuses were used. Cytospin slides were generated from tissue specimens for fluorescent in situ hybridization (FISH) and labeled with X and Y chromosome probes. Under fluorescent microscopy, polymorphonuclear cells (PMNs) were identified as having two XX signals (maternal) or a single X and Y pair (fetal).
Results: Maternal PMNs comprised 89% and 91% of the cellular response in the groups with and without clinical chorioaminionitis, respectively. This difference in the two groups was not statistically significant.
Conclusions: The dominant contribution of PMNs seen in preterm severe histologic chorioamnionitis is maternal in origin. This response is similar in the presence or absence of clinical chorioamnionitis.