The maternal-fetal interface, a chimeric structure, is formed when fetal cytotrophoblasts (CTBs) from the placenta invade the uterine wall and its resident vasculature. In preeclampsia (PE), interstitial and endovascular invasion are often shallow, and fewer spiral arterioles are breached in toto. Our previous work has shown that faulty CTB differentiation to an invasive phenotype is a contributing factor. Here, we have tested the hypothesis that the constellation of morphological and molecular defects that are associated with PE are unique to this condition. Specifically, we have compared the histology of the maternal-fetal interface and CTB expression of stage-specific antigens in PE and in preterm labor (PTL) with or without inflammation. In the absence of inflammation, biopsies obtained after PTL were near normal at histological and molecular levels. In accord with previously published data, PE had severe negative effects on the endpoints analyzed. Biopsies obtained after PTL with inflammation had an intermediate phenotype. Our results suggest that the maternal-fetal interface from cases of PTL without inflammation can be used for comparative purposes, e.g., as age-matched controls, in studies of the effects of PE on cells in this region.