A new study published in The BMJ has found that women who take birth control pills that use newer types of the hormone progestogen have three times the risk of developing blood clots compared to women not taking the oral contraceptive. Blood clots have been a known risk of taking the pill since the 1990s, and developers have been changing the progesterone levels of the pill since it was first introduced in 1960 in order to lower side effects like weight gain and acne.