Why do girls have their periods together?

Answer by  Ali41 (1593)

Woman who live or work in close proximity tend to regulate their cycles together. This phenonmenon happens because woman exude hormones that must indicate where they are in their cycle. Some say that if there is an alpha female in the group, that woman will regulate towards that person's cycle.

Answer by  rbiales (3441)

Women tend to cycle together because their hormones influence each other and modify each others' cycles. Most often when this has been studied the most dominant woman has the most effect on everyone elses' cycles. This can also happen when women who use hormonal birth control decide to take their pills on the same schedule.

Answer by  annie52foof (1459)

I think it has something to do with the hormones ending up the same the more you are around another woman.

Answer by  Gabriel (2146)

There's one theory that they get their periods around the same time because when the pheromones of one changes due to menstruating, the other tend to trigger as well.