Understanding your menstrual cycle is essential for your good health. The monthly pattern that occurs regularly in most women, from puberty to menopause, is called the menstrual cycle. Every cycle is divided into two parts—before ovulation and after ovulation. In a 28-day cycle, for example, the pattern usually follows this timing:
- The beginning of the cycle, called Day 1, is the day bleeding begins. The flow usually lasts about three-to-five days. Usually by Day 7, certain hormones cause some of the eggs in the ovaries to start ripening. Between Day 7 and 11, the lining of the uterus begins to thicken. The influence of additional hormones after Day 11 causes the egg that is most ripe to be released on about Day 14 in women who have a 28-day cycle. The other ripening eggs stop growing and dry up. That is part one of your cycle.
- In part two, the egg travels down the fallopian tube toward the uterus. If a single male sperm unites with the egg while it is in the tube, the fertilized egg may travel on and attach to the spongy lining of the uterus. Pregnancy begins if this “implantation” occurs. If fertilization doesn’t take place, the egg cell will break apart in a day or two. About Day 25, hormone levels drop. This causes the lining of the uterus to break down, and in a few days it is shed in a menstrual period. Another cycle has begun.
For some women, cycles recur fairly regularly—every 28 days. But the number of days in each cycle can vary from woman to woman, from every 21 to every 35 days. In fact, a few women have only three or four cycles a year.
The first part of the cycle, from the first day of menstruation to ovulation, may vary from 13- 20 days in length. The length of the first part is not only different from one woman to another, but also differs in some women from month to month. It is during this critical first part of the cycle that fertilization can occur. Such common circumstances as sickness, worry, physical exertion, and even sudden changes in climate may occasionally upset a regular patter by shortening it or extending it.
The second part of the cycle, from ovulation to the first day of menstruation, is about the same length in all women. The egg is released consistently 14-16 days before the onset of menstruation, regardless of the length of a woman’s menstrual cycle.
There are a few women who believe they can tell when the egg has been released from the ovary. Some report having a slight pain in the back, or on the right or left side of the lower abdomen. This pain is sometimes called mittleschmerz—German for “middle pain.”