Second-trimester histopathological placental findings in maternal-fetal inflammatory response syndrome.

Immature delivery is frequently associated with a maternal-fetal inflammatory response at the placental level. The aims of this study were to determine the prevalence, staging, and grading of histological findings (associated with acute maternal-fetal inflammatory response syndrome) in placentas of immature fetuses and to establish the relationship between maternal and fetal responses and its frequency distribution by fetal weight. The studied placentas corresponded to fetuses with weights ranging between 12 g and 625 g. The inflammatory response was classified according to the criteria published by the Perinatal Section of the Society for Pediatric Pathology. Of the 354 placentas analyzed, 231 (65.3%) showed acute inflammatory response. In 98.7% of the cases, inflammation was classified as maternal inflammatory response (MIR) and in 49.8% as fetal inflammatory response (FIR). In 49.1% of the cases, MIR was accompanied by FIR, whereas only 3 cases of FIR did not show MIR. As their stages increased, fetal response rates and the severity of MIR and FIR grew at higher stages of maternal response. Although the frequency of MIR was similar in different fetal weight groups, that of FIR increased with weight and gestational age.