The menstrual cycle – a fascinating rhythm of the female body

The menstrual cycle is a hormonally controlled process that repeats on average every 28 days and comprises several important phases. It begins on the fi rst day of menstrual bleeding and ends on the day before the next bleeding. The cycle prepares the body for a possible pregnancy.

Menstrual phase (approximately days 1 to 5) 

Menstruation begins with the shedding of the uterine lining that built up during the previous cycle. Blood and tissue flow out through the vagina. This phase usually lasts 3 to 7 days. During this time, hormone levels (estrogen and progesterone) are low.

Follicular phase / proliferative phase (approximately days 1 to 14)

Parallel to menstruation, the maturation of several follicles begins in the ovary under the influence of FSH (follicle-stimulating hormone). From these, a dominant follicle develops containing an egg cell. It produces increasing amounts of estrogens, which lead to the rebuilding and thickening of the uterine lining. The cervix becomes more permeable, and the cervical mucus becomes thinner—favorable conditions for fertilization.

Ovulation (around day 14)

Shortly before ovulation, estradiol (estrogen) reaches its peak, triggering a strong surge of LH (luteinizing hormone) from the pituitary gland. This LH surge causes the dominant follicle to rupture and release the egg into the fallopian tube—the moment of ovulation. The egg can be fertilized for about 12 to 24 hours.

Luteal phase / secretory phase (approximately days 15 to 28)

After ovulation, the ruptured follicle transforms into the corpus luteum, which produces progesterone. This hormone prepares the uterine lining to receive a fertilized egg. If fertilisation does not occur, the corpus luteum regresses, progesterone levels fall, and the lining is shed—marking the beginning of a new cycle with menstruation.

The menstrual cycle is a complex interplay of hormones and physiological changes that optimally prepares the body for pregnancy. Ovulation is the key mechanism that releases the egg and makes fertilisation possible. These processes are fascinating because they repeat every month and ensure the continuation of human life. Changes or disruptions in the cycle can provide important insights into a woman’s health and play a role in fertility or contraception.