In some women, combination hormonal birth control can increase the risk of blood clots, which can cause a pulmonary embolism (PE, a blood clot that blocks a blood vessel to the lungs). However, the overall risk of a PE is very low and it is actually higher for pregnant women than for nonpregnant women who take hormonal contraceptives. The birth control patch and pills with higher levels of the progestin drospirenone pose a higher risk compared to other forms of hormonal birth control.