For some girls and women, the entire menstrual cycle and terms associated with it can be confusing. The monthly periods (menstruation) are seen as a few days of inconvenience but beyond this, there is little understanding of the complex and fascinating changes occurring in the female body. Although the monthly periods are at times seen, both personally and culturally, as a negative occurrence in a women’s life, it is a representation of her fertility and the renewal of this ability in preparation for future pregnancy. The menstrual cycle is the period of on average 28 days where a number of changes driven by hormones occur in the female body in preparation for pregnancy and then ‘resetting’ of the system should pregnancy not occur. It is marked by two distinct occurrences – ovulation and menstruation.
The menstrual cycle starts on the first day of the last menstrual period (LMP) and the first phase continues till ovulation. This initial period is known as the follicular phase. At the start of this phase, the level of the female hormone estrogen is low and this triggers the pituitary gland to secrete a hormone known as follicle-stimulating hormone (FSH). By acting on the ovaries, FSH can then mature the follicles in the ovary. The maturing follicles then start secreting estrogen.
The presence of this estrogen signals the pituitary gland to secrete another hormone known as luteinizing hormone (LH). The level of LH rises in the bloodstream for a period known as the ovulatory phase. It marks the upcoming event of ovulation. LH acts on the ovaries causing one of the maturing follicles to burst and release an egg cell (ovum). This is known as ovulation. The other maturing follicles disintegrate.
The ovulatory phase and ovulation is marked by certain signs and symptoms that may not be prominent in every woman. However, it can serve as important signals of the best time in a woman’s cycle to fall pregnant. The more reliable of these signs and symptoms includes :
- Changes in cervical mucus where it appears clear and slippery (similar to egg-whites).
- Small rise in body temperature by about 0.4 to 0.6 degrees Farenheit.
- Mild pain or cramping without menstruation which is not always present in every woman.
The last phase in the menstrual cycle is known as the luteal phase. It is the time from ovulation till the onset of menstruation (monthly periods). The role of the follicle that has burst and released the egg is not complete once ovulation occurs. Instead the remnants of this follicle, now referred to as the corpus luteum, starts secreting another important hormone known as progesterone. The inner lining of the uterus, known as the endometrium, now needs to prepare for a possible pregnancy and it is the role of progesterone to coordinate this preparation. Should the egg cell be fertilized by a sperm cell from a male, this fertilized egg needs to be nourished and a suitable endometrial structure is needed for its implantation.
However, if fertilization does not occur then the now thickened endometrium is not needed and the entire system has to essentially ‘reset’ itself. The egg cell disintegrates, the endometrial lining is sloughed off and evacuated from the uterus via the vagina (menses). This occurs over a period of 4 to 7 days and is referred to as menstruation. The moment menstruation begins marks the end of the previous cycle and the start of a new cycle.