Cytologic findings in postpartum and postabortal smears.

A study was undertaken to evaluate the cytologic features of pregnancy-induced cell patterns (PIP) observed in postpartum and postabortal cervicovaginal smears. A total of 3,000 PIP were evaluated and studied by an indirect immunofluorescent technique using human chorionic gonadotropin (HCG). Three characteristic types of PIP were demonstrated. In type I PIP, the cells had a sheetlike arrangement with a fine chromatin pattern and were thought to be of decidual origin. Type II PIP were shed in clumps and had round nuclei, cytoplasmic vacuoles and coarse chromatin. They were thought to originate in the endometrium with the Arias-Stella reaction. Type III PIP were large and had large nuclei with marked atypism. They were thought to be cytotrophoblasts. Almost all of the type III PIP were positive with the anti-HCG stain. It is concluded that this classification and analysis is significant and could reduce the number of false-positive cytology reports on postpartum and postabortal smears.