If you start using Seasonale you will probably experience 3-4 menstrual periods per year but they will be unpredictable and be accompanied by larger bleeding. That’s why some doctors don’t recommend this particular type of contraceptive.
Serious side effects (blood clots, heart attack, and stroke) are very rare and are generally across the board for all types of hormonal contraception. The risk for such side effects, however, is increased for women who smoke.
Women on birth control pills do not have a higher risk for infections except for yeast infections. It is true that regular menstruation has a protective role against genital infections, regardless of whether or not she takes oral contraceptive birth control pills.