Dra. Joana Faria - Ginecologist-Obstetrician - Lisbon, Portugal
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Menstrual cycle alteration

The menstrual cycle is the monthly series of changes a woman's body goes through in preparation for the possibility of pregnancy. If no hormonal contraception is done, each month, one of the ovaries releases an egg (process called ovulation). At the same time, hormonal changes prepare the uterus for pregnancy. If ovulation takes place and the egg isn't fertilized, the lining of the uterus sheds through the vagina. This is the so-called menstrual period.

Girls start menstruating at the average age of 12. However, girls can begin menstruating as early as 8 years of age or as late as 16 years of age. Women stop menstruating at menopause, which occurs at about the age of 51.

The menstrual cycle begins on the first day of your menstruation and continues up to (but not including), the fist day of your next period. The cycles usually range from 21-35 days, with an average around 28 days. Periods usually last between 2-7 days and blood loss during a period is around 30 to 40 millilitres (ml).

Alterations in what you consider to be your normal cycle can be a cause for concern.

Tracking your menstrual cycle can help you find out what's normal in your case. Keep a record of your menstrual cycle on a calendar and note the start date every month for several months in a row to identify the regularity of your menstrual cycle.

When should I contact my doctor because of my period? Contact your doctor if:

  • You have not started menstruating by the age of 16
  • Your period stops suddenly (amenorrhea)
  • You are bleeding for more days than usual
  • You are bleeding more heavily than usual or you notice loss of blood clots (menorrhagia)
  • You have severe pain during your period (dyspareunia)
  • You have bleeding between periods (metrorrhagia)
  • You suddenly feel sick after using tampons
  • You think you might be pregnant—for example, you have had sex and your period is at least five days late
  • Your period has not returned within two months after stopping birth control pills and you know you are not pregnant
  • You have any questions or concerns about your period or possible pregnant

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