Menstruation, also called menses, is just one part of the menstrual cycle in which your body prepares for pregnancy each month. A menstrual cycle is counted from the first day of one period (the first day of bleeding) to the first day of the next period. An average cycle is 28 days, but anywhere from 23 to 35 days is normal.
At the beginning of your cycle, the hormones estrogen and progesterone are at very low levels. During menstruation, levels of estrogen, which is made by your ovaries, start to rise and make the lining of your uterus grow and thicken. In the meantime, an egg (ovum) in one of your ovaries starts to mature. It is encased in a sac called the Graafian follicle, which continues to produce estrogen as the egg grows.
At about day 14 of a typical 28-day cycle, the sac bursts and the egg leaves your ovary, traveling through one of the fallopian tubes to the uterus. The release of the egg from the ovary is called ovulation.
After the egg is expelled, the follicle sac (now called a corpus luteum) remains in the ovary, where it starts producing hormones, mainly progesterone. The rising levels of both estrogen and progesterone help build up the uterine lining to prepare for pregnancy.
The few days before, during, and after ovulation is your "fertile period"—the time when you can become pregnant. Because the length of menstrual cycles varies, you may ovulate earlier or later than day 14. It's even possible for you to ovulate while you still have your period if that month's cycle is very short. (Stress and other things can sometimes cause a cycle to be shorter or longer.) It is during this fertile period that conception and pregnancy can occur. Sperm from a man fertilizes the egg.
The fertilized egg attaches to the uterus, the growing pregnancy releases a hormone (hCG), which stimulates the corpus luteum. The corpus luteum makes all the progesterone needed to keep the egg implanted and growing until a placenta (an organ connecting the fetus to the mother) develops. The placenta then makes hormones and provides nourishment from the mother to the growing embryo.
If an egg is not fertilized and you don't get pregnant, the corpus luteum stops making hormones and gets reabsorbed in the ovary. Estrogen and progesterone levels drop again, the lining of the uterus breaks down (in an orderly way), menstruation (bleeding) begins, and the cycle starts all over again.
This cycle will continue every month starting from about age 11-16 years old to an average age of 50 years old when menopause signals the end of menses and the ability to become pregnant.
Menorrhagia (Heavy Bleeding)
Most women lose an average of about 2 ounces (60 ml or 1/4 cup) of blood or less during normal menstruation. However, in up to 14% of women, menstrual bleeding can be significantly heavier and/or longer—a condition known as menorrhagia. Menorrhagia can be caused by a number of conditions and can lead to anemia, infertility, and other complications.
Amenorrhea (Absence of Menstruation)
Amenorrhea, or the absence of menstruation, is categorized as primary or secondary. Primary amenorrhea occurs when a girl does not start to menstruate within the normal time frame of sexual development. This usually occurs by age 14; definite primary amenorrhea is diagnosed if there is no menses by age 16.
Secondary amenorrhea occurs when previously normal menstrual periods are absent for at least three cycles (for reasons other than menopause). Amenorrhea can be caused by hormonal imbalances, hypothyroidism, eating disorders, psychiatric disorders, low or high body fat, rapid weight loss, excessive exercise or intense physical training, and a number of medical conditions. Due to the underlying low estrogen, prolonged amenorrhea can lead to a decrease in bone density, an increased risk of osteoporosis, and infertility.
Please be aware that this information is provided to supplement the care
provided by your physician. It is neither intended nor implied to be a
substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER
IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the
advice of your physician or other qualified health provider prior to
starting any new treatment or with any questions you may have regarding a