UTERINE ALLERGY - A CAUSE OF PRETERM BIRTH

Objective: To identify the origin of eosinophils in cases of eosinophi l-associated preterm delivery. Methods: From an established set of 465 consecutive nonanomalous singleton infants delivered at 22-32 weeks' gestation, we retrieved 161 cases of preterm delivery following sponta neous onset of preterm labor, 78 cases with maternal preeclampsia, 33 cases of abruption, and 193 cases of premature rupture of membranes (P ROM). Charts were reviewed, and the placenta, umbilical cord, and memb ranes were examined histologically. In cases with extravascular eosino phils showing evident gradient toward the amniotic cavity, the origin of the eosinophils (fetal or maternal) was determined by the proximity to fetal or maternal vessels. Results: Histologic evidence of an eosi nophilic gradient toward the amniotic cavity was present only in the f etal (including umbilical cord and chorion) compartments. This eosinop hilic gradient was present in 19% (90 of 465) of preterm delivery case s and was significantly more common in cases of PROM (54 of 193, 28%) and preterm labor (34 of 161, 21%) than abruption (two of 33, 6%) and preeclampsia (none of 78) (P < .001). In 84 of 90 cases (93%), the eos inophilic gradient was present along with multiple histologic indicato rs of acute intrauterine inflammation. Conclusion: An eosinophilic gra dient toward the amniotic cavity, present in nearly a fifth of cases o f preterm delivery, is probably of fetal origin, making it unlikely th at a maternal ''allergy-like'' mechanism is a cause of preterm deliver y.