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Understanding Your Menstrual Cycle

menstrual cycle

Uh-oh! It’s that time of the month again! You’re clutching your abdomen, because it hurts down there. Soon enough, it’ll be time to whip out a menstrual pad or tampon to keep the leaking blood from soiling your clothes.

But why menstruate? Why does this happen every month?

In truth, the menstrual cycle is the body’s way of preparing for the possibility of a pregnancy. Understanding your menstrual cycle is important as it can help you to manage menstrual symptoms more effectively, help you to become pregnant or support you in identifying any potential problems.

The Menstrual Cycle – An Overview

The menstrual cycle is an interplay between numerous organs. Throughout the cycle, the ovaries, uterus and brain communicate and signal to one another through hormones. Rising levels of estrogen cause an ovary to release an egg (ovulation) and the lining of the uterus (or womb) to thicken. During the second half of the cycle, the increase in the hormone progesterone helps prepare the womb for implantation, in the event of a pregnancy. If no pregnancy occurs, levels of estrogen and progesterone decrease and the lining of the womb begins to shed away, leading to menstruation.

“The menstrual cycle begins on the first day of a period and ends with the start of the next period,” says Dr. Ruchi Amin, Reproductive Endocrinologist with GENESIS.  “It can last from 21 to 35 days, with the average cycle lasting around 28 days. However, cycle lengths can vary between cycles and may change over a womans reproductive life.”

Phase One – The Follicular Phase

Taking place in the ovaries, this phase usually lasts from the start of a period until ovulation (at around 14 days). During the follicular phase, the pituitary gland produces a hormone called follicle stimulating hormone (FSH), which signals the ovaries to begin to prepare an egg for ovulation.

As a result, follicles (fluid filled sacs which contain an egg) begin to rise to ovary’s surface. As one follicle becomes dominant and reaches maturity, the others shrink back. The dominant follicle also produces estrogen during its growth.

The increase in estrogen produced by the follicles causes the lining of the uterus (endometrium) to begin to thicken, and continue to do so until ovulation occurs. This allows the uterus to prepare a place for implantation and growth of a fertilized egg in the event of a pregnancy.

Phase Two – Ovulation

Ovulation is the stage at which an egg is released from the ovary into the fallopian tube. When the dominant follicle reaches maturity and the level of estrogen is high enough, a signal is sent to the brain. This results in an increase in the luteinizing hormone (LH), which causes ovulation to occur. Ovulation typically occurs around 13-15 days before the start of the next period. Following the release of the egg, the follicle seals over and forms a structure called the corpus luteum.

Phase Three – The Luteal Phase

During this phase, the levels of both FSH and LH decrease. At the same time, the corpus luteum produces progesterone which prevents the endometrial lining (in the uterus) from being shed and supports early pregnancy.

If no fertilization takes place, the corpus luteum disintegrates, causing a decrease in estrogen and progesterone levels. The endometrium secrets many chemical messengers during this phase, with the prostaglandins being the most notable, as they cause changes to other nearby cells.

“Two prostaglandins in particular cause the uterine muscles to contract, or cramp. If fertilization occurs, prostaglandin production is inhibited. If no pregnancy occurs, the decreased levels of estrogen and progesterone, alongside with the effects of the prostaglandins, cause the tissue of the endometrium to begin to shed, leading to menstruation,” explains Dr. Alexander Kotlyar, Director of Resident Education with GENESIS.

Using Ovulation Prediction Kits

Ovulation prediction kits work by measuring the concentration of LH in your urine. Although small amounts of LH are always present, there is an increase in the 24-48 hours prior to ovulation occurring. Some more advanced kits also measure estradiol. This is a form of estrogen which usually peaks on the day of ovulation itself.


Understanding your menstrual cycle can you help you to identify and understand problems you may be experiencing during your cycle. Tracking your symptoms throughout your cycle can help you feel more in-control and anticipate changes. Additionally, it can also help you notice patterns and identify if anything unusual is taking place. This awareness can help you utilize the advice and support of healthcare professionals.

So, the next time you feel pain and see blood down there, you’ll know the truth about menstruation.

Original post July 21, 2021
Updated July 11, 2024

Regina Wheeler is an experienced e-learning consultant at PhD Kingdom. In her spare time, Regina enjoys spending time with her family and exploring the outdoors.

If you would like to learn more about GENESIS Fertility New York or are ready to schedule an appointment, please speak with one of our representatives at 718-GENESIS.

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