Beginning at about age 12, girls begin to have periods, or menstruate. However, menstrual periods may begin at any age between the ages of eight and 15 and still be normal. This process is governed by complex interactions among hormones produced by the brain and ovaries. Like many health conditions, Dr. Wilburn will tell you there’s considerable variation in “normal” menstrual cycles.
When a girl is born, her body already contains millions of immature eggs. At puberty, the eggs begin to mature under the influence of hormonal changes. When an egg matures, it leaves the ovary and travels down the Fallopian tube to the uterus. If pregnancy occurs, the egg will become embedded in the uterus and develop into a baby. If not, the lining of the uterus sloughs off and becomes the blood seen in a woman’s period.
It’s normal for a girl’s periods to be irregular in timing and amount when they first begin. Although the average menstrual cycle is 28 days, teen cycles can vary from 21 to 45 days and still be considered normal. In adult women, 21 to 35 days is considered a normal variation. The length of the period can also vary, with an average of three to five days and a common range of two to seven days. Some women may have cramps with a period while others don’t.
Menstrual periods continue until menopause when fertility wanes and periods become less regular and finally stop. The average age of menopause in the US is around 50, but menopause anywhere between the ages of 45 to 55 is considered normal. Some women may enter what is called perimenopause in the early 40s. A woman’s periods will still be regular, but she may develop other menopausal symptoms like hot flashes or mood swings. Eventually, menstrual periods become irregular, and the interval between them lengthens until they stop.