Combined oral contraceptive
Noretynodrel (and norethisterone) were subsequently discovered to be contaminated with a small percentage of the estrogen mestranol (an intermediate in their synthesis), with the noretynodrel in Rocks 1954–5 study containing 4–7% mestranol. When further purifying noretynodrel to contain less than 1% mestranol led to breakthrough bleeding, it was decided to intentionally incorporate 2.2% mestranol, a percentage that was not associated with breakthrough bleeding, in the first contraceptive trials in women in 1956. The noretynodrel and mestranol combination was given the proprietary name Enovid.The first contraceptive trial of Enovid led by Celso-Ramón García and Edris Rice-Wray began in April 1956 in Río Piedras, Puerto Rico. A second contraceptive trial of Enovid (and norethisterone) led by Edward T. Tyler began in June 1956 in Los Angeles. On January 23, 1957, Searle held a symposium reviewing gynecologic and contraceptive research on Enovid through 1956 and concluded Enovids estrogen content could be reduced by 33% to lower the incidence of estrogenic gastrointestinal side effects without significantly increasing the incidence of breakthrough bleeding.While these large-scale trials contributed to the initial understanding of the pill formulations clinical effects, the ethical implications of the trials generated significant controversy. Of note is the apparent lack of both autonomy and informed consent among participants in the Puerto Rican cohort prior to the trials. Many of these participants hailed from impoverished, working-class backgrounds.
Also in 1957, the FPA established a Council for the Investigation of Fertility Control (CIFC) to test and monitor oral contraceptives which began animal testing of oral contraceptives and in 1960 and 1961 began three large clinical trials in Birmingham, Slough, and London.In March 1960, the Birmingham FPA began trials of noretynodrel 2.5 mg + mestranol 50 µg, but a high pregnancy rate initially occurred when the pills accidentally contained only 36 µg of mestranol—the trials were continued with noretynodrel 5 mg + mestranol 75 µg (Conovid in the UK, Enovid 5 mg in the U.S.). In August 1960, the Slough FPA began trials of noretynodrel 2.5 mg + mestranol 100 µg (Conovid-E in the UK, Enovid-E in the U.S.). In May 1961, the London FPA began trials of Scherings Anovlar.In October 1961, at the recommendation of the Medical Advisory Council of its CIFC, the FPA added Searles Conovid to its Approved List of Contraceptives. On December 4, 1961, Enoch Powell, then Minister of Health, announced that the oral contraceptive pill Conovid could be prescribed through the NHS at a subsidized price of 2s per month. In 1962, Scherings Anovlar and Searles Conovid-E were added to the FPAs Approved List of Contraceptives. France
On December 28, 1967, the Neuwirth Law legalized contraception in France, including the pill. The pill is the most popular form of contraception in France, especially among young women. It accounts for 60% of the birth control used in France. The abortion rate has remained stable since the introduction of the pill.