In comparison, venous thromboembolism occurs in 100–200 per 100.000 pregnant women every year.One study showed more than a 600% increased risk of blood clots for women taking COCPs with drospirenone compared with non-users, compared with 360% higher for women taking birth control pills containing levonorgestrel. The U.S. Food and Drug Administration (FDA) initiated studies evaluating the health of more than 800,000 women taking COCPs and found that the risk of VTE was 93% higher for women who had been taking drospirenone COCPs for 3 months or less and 290% higher for women taking drospirenone COCPs for 7–12 months, compared with women taking other types of oral contraceptives.Based on these studies, in 2012 the FDA updated the label for drospirenone COCPs to include a warning that contraceptives with drospirenone may have a higher risk of dangerous blood clots.A 2015 systematic review and meta-analysis found that combined birth control pills were associated with 7.6-fold higher risk of cerebral venous sinus thrombosis, a rare form of stroke in which blood clotting occurs in the cerebral venous sinuses. Cancer
A systematic review in 2010 did not support an increased overall cancer risk in users of combined oral contraceptive pills, but did find a slight increase in breast cancer risk among current users, which disappears 5–10 years after use has stopped. Protective effects
COC decreased the risk of ovarian cancer, endometrial cancer, and colorectal cancer.
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.