The length of a menstrual cycle varies significantly from woman to woman. The average length of a menstrual period is approximately five days. Again, some women experience shorter or longer periods, with a range of approximately one to eight days. In addition, studies have shown that when several young women live together and do not take oral contraceptives, they tend to menstruate at the same time of the month. Researchers attribute this synchronization of menstrual cycles to the secretion of pheromones, chemicals that may influence biological activity.
Synchronization is disrupted if women live with men.
This occurs once every 28 days on the first day of bleeding. As an egg matures, the cells around it also grow and form a follicle that releases estrogen. LH causes the most mature egg in the ovary to be released around day 14 of the cycle. This act of releasing an egg is called ovulation. Sometimes, more than one egg is released, which can result in twins, triplets, etc. if all of the eggs are fertilized by sperm.