Menstruation is what most people call your periods. During menstruation, the lining of the uterus is removed through the vagina. Menstruation usually occurs every month and lasts between 3 and 7 days.

The first menstrual period
Most women have their first period between 9 and 16 years.
If you are 16 years and never had your menstrual period, it is recommended that you consult with a provider of health care.

The menstrual cycle is the timeframe from the first day of a menstrual period until the first day of the next. A normal menstrual cycle may last only 21 days or more than 35 days. In most women, menstrual cycle lasts between 25 and 30 days. However, it is normal that the number of days in each cycle varies from month to month.

The menstrual flow usually lasts between 3 and 7 days but may take a little more or less. Once the menstrual period ends, hormones cause some of the eggs from the ovaries begin to develop or mature. The hormones also cause the lining of the uterus to bulge.

Approximately half of the menstrual cycle, a mature egg leaves one of the ovaries. This is called ovulation. Most women do not feel when they’re ovulating, but others feel pain in lower abdomen during ovulation. Some women have mild loss of blood a day or two after ovulation.

After leaving the ovary, the egg travels through the fallopian tubes toward the uterus. As the egg travels through the fallopian tubes, the uterus continues to form a soft spongy lining. This coating is where a fertilized egg attaches to the start of the pregnancy. If no pregnancy occurs, the lining breaks down and the blood and tissue are removed from the uterus through the cervix. This is the menstrual period. During an average menstrual period is lost between 4 and 12 teaspoons of menstrual fluid.

Pregnancy and Menstrual cycle
It is more likely to occur if you have had unprotected vaginal intercourse during the six days prior to ovulation. It is also possible, but less likely, the day after ovulation. To prevent pregnancy, some women use observation methods to predict when fertility will ovulate. During those days of the cycle, they abstain from vaginal intercourse or use condoms or other contraceptive methods.