After three years of extensive botanical research, he discovered a much better starting material, the saponin from inedible Mexican yams (Dioscorea mexicana and Dioscorea composita) found in the rain forests of Veracruz near Orizaba. The saponin could be converted in the lab to its aglycone moiety diosgenin. Unable to interest his research sponsor Parke-Davis in the commercial potential of synthesizing progesterone from Mexican yams, Marker left Penn State and in 1944 co-founded Syntex with two partners in Mexico City. When he left Syntex a year later the trade of the barbasco yam had started and the period of the heyday of the Mexican steroid industry had been started. Syntex broke the monopoly of European pharmaceutical companies on steroid hormones, reducing the price of progesterone almost 200-fold over the next eight years.Midway through the 20th century, the stage was set for the development of a hormonal contraceptive, but pharmaceutical companies, universities and governments showed no interest in pursuing research. Progesterone to prevent ovulation
Progesterone, given by injections, was first shown to inhibit ovulation in animals in 1937 by Makepeace and colleagues.In early 1951, reproductive physiologist Gregory Pincus, a leader in hormone research and co-founder of the Worcester Foundation for Experimental Biology (WFEB) in Shrewsbury, Massachusetts, first met American birth control movement founder Margaret Sanger at a Manhattan dinner hosted by Abraham Stone, medical director and vice president of Planned Parenthood (PPFA), who helped Pincus obtain a small grant from PPFA to begin hormonal contraceptive research.
This thick ring of membranes is composed of a double fold of amnion and chorion with degenerated decidua vera and fibrin in between. Blood vessels, supplying nutrients and carrying waste products to and from the developing fetus, radiate from the umbilical cord insertion to as far as the ring of membranes, and then disappears from view. Signs & Symptoms
A circumvallate placenta does not always induce associated symptoms during pregnancy, making it extremely difficult to diagnose a circumvallate placenta in asymptomatic mothers. In symptomatic mothers, physicians may be able to detect a circumvallate placenta based on the presentation of the following signs. Vaginal bleeding: A circumvallate placenta can increase the risk of frequent vaginal bleeding during the first trimester of pregnancy. In a study conducted with 92 women with a circumvallate placenta, it was concluded that incidences of vaginal bleeding were significantly higher in women with a circumvallate placenta during all three trimesters when compared to the control group. However, a noted limitation of the study considered by the researchers was that because the study included such a small number of women, the obtained results may not be fully representative of the general population. Because the chorionic plate is much smaller than the basal plate in a circumvallate placenta, vaginal bleeding tends to occur at this site where the placenta is exposed and uncovered. In mothers presenting with vaginal bleeding, circumvallate placenta should be suspected as a possible cause of the vaginal bleeding.