Menstruation
Changes to a female’s body will happen as they grow. These include changes in breast tissue and growth of pubic and underarm hair. About 2-3 years after breasts start to develop, the first period can happen. In the United States, the average age of menarche (first-time menstruating) typically occurs between ages 12 and 13.
How does menstruation work?
Menstruation is a cycle that is separated by the timing and events involving the ovary and the uterus. Menstrual bleeding, a period, starts on day 1 of the menstrual cycle. This is when the fluid that contains blood and tissue leaves the body through the vagina. This fluid is a build-up of the uterine lining.
About once a month, an ovary releases an egg (ovulation), traveling through the fallopian tube, with the goal of reaching the uterus. If this egg is fertilized, it should travel to the uterus, where the uterine lining has thickened to implant and begin growing a baby. By the time the egg reaches the uterus, the lining should be built up to create an environment that could support a pregnancy if the egg were to be fertilized. If the egg is not fertilized, then about 10-14 days after ovulation, the thick lining from the uterus will break down and leave the vagina, resulting in a period. It may take about six years to become a regular cycle.
What is considered “normal” menstrual bleeding?
Regular menstrual cycles may last 21-45 days, with bleeding lasting 2-7 days. Usually, a period starts heavier and slows toward the end. Average blood loss can range from a few tablespoons to one-quarter cup a day. When periods start, many of the cycles through the first year happen without ovulation (anovulatory), and common period symptoms, such as pain and cramps (dysmenorrhea), do not occur. Menstrual cycles in adolescents are not as predictable as in adults, but by the third year, menstrual intervals should be 21-34 days. Cycles that are out of the “norms” should be discussed with your physician.
For additional information about menstruation and heavy menstrual bleeding (HMB), access the following resources to learn more: