One would assume that birth control pills, which contain estrogen, would lower blood pressure. However, the estrogen in oral contraceptive pills causes a small but detectable increase in blood pressure in most women, which means that hypertension is two to three times more common in women on the pill. The Walnut Creek Contraceptive Drug Study, which included 11,672 women, showed an increase of 5 to 6 points in systolic blood pressure (the higher of the two readings) and 1 to 2 points in diastolic pressure for white women, with African-American women experiencing less of an increase. That risk becomes greater with age, duration of pill use and increased body mass.
A prudent approach to oral contraceptive use is to monitor blood pressure at least every 6 months. If high blood pressure is found, then a decision to discontinue the pill should be based on the degree of hypertension, the potential hazards of pregnancy, and the individual's risk of developing heart disease.