The day you get your monthly period is considered the first day of your menstrual cycle; the last day of your cycle is the day before your next period begins. The length of your cycle and the duration of your period are two different things.
What is the typical length of a menstrual cycle and the duration of a period?
The average cycle is 28 days long. Bleeding will usually last about four days. However, the range of what is considered normal is broad; women can have a cycle that lasts anywhere from 21 to 35 days, and a normal period can last from one to eight days [1].
What are the cycle phases?
The cycle is divided into two phases: before and after ovulation. Ovulation itself is also sometimes described as a separate phase.
Phases of the menstrual cycle
The first phase is called the follicular phase. It lasts 10 to 16 days, or an average of 14 [2]. It gets its name from the follicle-stimulating hormone (FSH). The pituitary gland produces this hormone and stimulates the growth of follicles in the ovaries. At the same time, under the influence of estrogen, the uterine lining (or endo.metrium) thickens
By the middle of the cycle, an egg cell will mature in one of the follicles, and the luteinizing hormone (LH) is released. The follicle ruptures and the egg cell releases into the abdominal cavity. This is called ovulation, which is when conception can occur. The egg cell then enters the fallopian tube and waits to meet a sperm.
The second phase of the cycle is called the luteal phase. A yellow body, called the corpus luteum, forms in place of the empty follicle. It produces the hormone progesterone, which prepares the uterine lining for embryo implantation. This period typically lasts around 14 days [3].
If conception occurs, the level of progesterone will continue to rise. The brain then receives a signal to cease menstruation. If pregnancy does not happen, the corpus luteum stops producing progesterone, and the non-useful mucous layer of the uterus disintegrates and detaches, causing bleeding. This process is observed monthly as another menstruation.
Is it normal for the length of my cycle to vary?
Fluctuations in your cycle of a few days in either direction are normal. But longer, more noticeable fluctuations can be a symptom of an anovulatory cycle. If ovulation does not occur, the yellow body will not form, progesterone levels will not rise, and the cycle is lost. Anovulatory cycles often happen during the first two or three years after menarche (the first menstruation of a woman’s life) and again after age 40, when menopause becomes closer [1].
