Every woman is different but the typical menstrual cycle is 28 days long. The length might be different from month to month and the cycle can vary from 24 to 45 days.
The total amount of blood that flows during an average period seems to be so much more than it actually is; it’s usually only about four teaspoons. But the range is between one and four tablespoons.
The follicular phase
The follicular phase is the first phase of the cycle. It lasts about 10 to 14 days. The uterine lining rebuilds in preparation for ovulation and hormones stimulate follicle development during this phase. The drop of estrogen levels triggers an increase of follicle-stimulating hormone (FSH) that promotes the growth of a group of follicles within the ovaries. One follicle will continue to develop into a mature egg. Hormones cause the mature follicle to burst and release the egg into the fallopian tube. This is the beginning of ovulation, which marks the end of the follicular phase.
The cycle enters the luteal phase with the ovulation of an egg from one of the ovaries. A surge of luteinizing hormone initiates ovulation. Estrogen and progesterone levels also rise during the luteal phase causing the endometrium (the lining of the uterus) to thicken in preparation for an embryo (a fertilized egg).
If one becomes pregnant, the embryo enters the uterus and implants itself in the endometrium within the first few days after ovulation. Human chorionic gonadotropin (HCG), produced by the placenta, interrupts the menstrual cycle by constantly stimulating the burst follicle (corpus luteum) to produce estrogen and progesterone. The high levels of estrogen and progesterone prevent the endometrium from shedding. If conception does not occur, estrogen and progesterone levels decrease, signalling the uterus to begin shedding the endometrium. The luteal phase lasts until the beginning of the next period.
Your period change in different ages
Our bodies are changes a lot during a lifetime. Our hair changes color, our skin becomes less hydrated, our metabolism slows down — and the same happens with our menstrual cycle. Hormonal changes, pregnancy and perimenopause have an impact on your menstrual cycle. You can go from having easier cramps to a heavier flow and more PMS mood swings. What can I expect decade by decade?
In your 20´s
After years of irregular periods during puberty, your periods have become more regular. When your period comes more or less monthly, you'll also start experiencing PMS, cramps and breast tenderness. If you weren't used to dealing with these side effects every month, it can be something of an unpleasant surprise. Going on or off birth control, or switching methods can cause changes in your flow or the length of your period. That´s not a problem. A missed period could be a sign of pregnancy but it could also be caused by extreme stress.
In your 30s
As you approach your late 30s, your periods may become less frequent or less regular. That´s perimenopause, the beginning of your body´s transition to menopause.
In your 40s and beyond
Your periods may get shorter and lighter, or come less frequently. Normal hormone changes cause your periods to be more irregular, and estrogen level fluctuation means you could start experiencing missed periods, a heavier flow, and longer stretches of PMS. Menopause occurs when your period stops completely. For most women, this happens in their late 40s or early 50s. When a woman is in this phase it also becomes more common with vaginal dryness (atrophy).