While hormonal birth control pills are generally safe, women with other contributing risk factors like high blood pressure, high cholesterol and those who smoke are at a higher risk of heart disease while on the pill. This is especially true once women reach the age of 35. Birth control pills increase blood pressure in some women, and when combined with advancing age and smoking will only raise the risk of cardiovascular disease.
Womenshealth.gov, part of the U.S. Department of Health and Human Services, tells us that birth control patches may actually expose women to higher doses of estrogen than those who take the pill. The greater exposure to the hormone may create blood clots, and therefore heart attack or stroke becomes more likely. Again, other risk factors like smoking, age and overall health come into play.
Only one more fact to go, and this one you may find surprising.