To sidestep Massachusetts and US laws, in 1956 Pincus and Rock took their study to Puerto Rico, which had no contraception laws at all. Birth control was popular on the island and 67 clinics already provided barrier methods and douches. In the Rio Piedra housing project, Pincus saw an ideal test population: large, fertile, motivated, and stationary.
The poor, undereducated young women selected were only informed the pill would prevent pregnancy, not that it was expiremental or might have risks. Pincus also thought the Puerto Rican trials would prove how easy the product was to use. If even they can do it, surely American women can!
After a year long study the medical director of the Puerto Rico Family Planning Association Dr. Edris Rice-Wray, who oversaw the trials, reported the results. Synthetic estrogen branded Enovid 100% effective when taken correctly. It also had a 17% rate of side effects, from mood swings to bloating and nausea. She said it was too much. The two men waved away her concerns. Surely the mood swings were psychosomatic and any other discomfort paled in comparison to pregnancy.
Three of the mothers under forty years of age in the Puerto Rico trials died. No autopsies were performed and Pincus did not investigate the causes of their deaths. High doses of estrogen can increase risk of heart disease and certain cancers. They can also cause blood clots, which can lead to pulmonary embolism, heart attack, and stroke. Later deaths in the US were linked to blood clots caused by hormonal birth control.
Enovid was approved by the Food and Drug Administration as a treatment for menstrual disorders in 1957. Droves of women reported unprecedented rates of menstrual distress. John Rock was a devout Massachusetts Catholic who wanted Vatican approval. Unlike banned birth control methods, it did not kill sperm, did not introduce a barrier, and did not prevent ejaculation. He included a period of placebo pills to allow for regular menstruation to make it seem more “natural” to the Church.