Menstruation is one part of the female cycle that occurs each month. The cycle starts with ovulation. Your ovaries are located up inside your abdomen. They contain all the eggs (ova) you�ll ever have that could become fertilized by a male�s sperm. Each month, an egg (ovum) matures and pops out of one of the two ovaries. This is called ovulation. Females usually start ovulating during puberty.  The egg travels from your ovary, through the fallopian tubes, and toward your uterus. As the egg travels, it sends a signal to your body to develop a thick lining of blood and tissue inside the uterus. The job of this lining is to help the egg attach to your uterus, should it meet up with a sperm and become fertilized. If this happens, the egg latches on to the thick lining of tissue and blood, and a pregnancy begins.

Now, if there�s no fertilization, there�s no pregnancy and no need for that thick lining to
nourish a pregnancy. The egg dies and the uterus releases the blood and tissue. That lining is your period. The blood and tissue usually leave your body slowly over five to seven days.

Ovulation occurs about 14 days before you begin bleeding or menstruating, which is when a woman is most likely to get pregnant.  Eggs only live about 24 to 36 hours. But
ovulation can be unpredictable, so it�s important to use birth control any  time you decide
to have sexual intercourse, no matter what time of month.