[From pill to pill: oral contraception, venous thrombosis and coagulation disorders]

"The pill" (oral contraception) is one of the most frequently used and efficient means of birth control. The pill was developed in the middle of the 1950s, and was prescribed in Europe from the early sixties onwards. Because millions of healthy young women in industrialized societies use oral contraceptives, even rare side effects receive a lot of attention. In the early 1960s "the pill" was associated with an increased frequency of arterial and venous thrombosis. However rare, these findings often engendered strong controversies. One of the reasons thereof was the uncertainty about the mechanism: it was not understood how the pill could cause an increased tendency towards thrombosis. In the past 5 years, epidemiologic, haemostatic and clinical research has led to new insights in how "the pill" causes venous thrombosis. These developments followed the discovery of "Activated protein C resistance" and the factor V Leiden mutation. The developments were accelerated by the finding that "third generation oral contraceptives" are associated with a higher risk of venous thrombosis. The lecture describes these new scientific insights.