In its report published Tuesday, the ANSM says more than four million women a year took oral contraceptives in the decade between 2001 and 2011.
Half of them took the third and fourth-generation pills, which have been introduced in the last 20 years and have now been shown to increase the risk of blood clots.
The agency estimates that contraceptive pills were linked to about 2,500 cases of blood clots a year and that about half of those cases could be attributed to the later-generation pills.
Blood clots can be deadly, causing strokes or heart attacks if they get lodged in the brain or the heart.
The use of third and fourth generation pills has been scaled back since January, when the health ministry calling on doctors not to prescribe them as a first option, due to the risk of blood clots.
The agency said that sales of the later-generation pills dropped by 34 per cent last month, following the health ministry’s warning.