Some types of birth control pills shorten a woman's menstrual period and reduce the menstrual flow, according to the University of Maryland Medical Center. Other types can stop periods entirely.
Columbia Health notes that it is also possible for a woman to change the dates of her period through use of birth control pills. To intentionally skip a period, a woman taking 28-day oral birth control should start a new group of active pills as soon as she reaches the end of the active pills in her previous pack, skipping the inert pills typically taken during menstrual periods. A woman taking a 21-day oral contraceptive should begin a pack of active pills on the day following completion of her previous active pack and eliminate the typical week with no pills.
Continuously taking active pills with no break prevents the occurrence of a period, according to Columbia Health. However, some light bleeding can still occur. Certain forms of oral birth control limit women's periods to only four times per year or less. The effectiveness of intentionally manipulating a woman's menstrual cycle with the use of oral birth control varies depending on the type of hormones. Periods that last longer than normal or include heavy bleeding are known as menorrhagia; the University of Maryland Medical Center advises women with this condition to consult their doctors.