Morphological studies on the placenta.

Morphological studies were done on 109 placentae of 6 to 43 gestational weeks. Soft x-ray figures are useful for detecting the development of the placenta, which is closely correlated to enlargement of cotyledon and vascular growth in the chorionic villi. At histological figures, chorionic villi, corresponding to intermediate mature villi at the early gestational weeks, reveal large size with edematous stroma and prominent interstitial cells. Their size becomes smaller with aging, with decreased interstitial cells and stroma. At the early gestational period until 23 weeks, chorionic villi are lined by two cell layers of S-(syncytial) and C-(cytotrophoblastic) cells. After 24 gestational weeks C-inner lining decreases in number. Syncytial knots become marked after 32 weeks. As aging, the intervillous space becomes narrow and is occupied by the small sized terminal and mature chorionic villi with congestive capillaries. Syncytial knots and fibrin deposit around chorionic villi are increased with placental aging. By the immunohistoenzymatical examination, S-lining is positive by hCG (human Chorionic Gonadotropin) at the early gestation, but is markedly positive by hPL(human Placental Lactogen) and SP-1 (Specific Protein 1) lately.