What is a menstrual cycle?
Something very important, according to the American Academy of Pediatrics and American College of Obstetrics and Gynecology.
A vital sign. Think: temperature, blood pressure, heart rate.
An elevated temperate can indicate a fever, potentially an infection. An elevated blood pressure can indicate a cardiac problem. An irregular menstrual cycle can indicate a localized reproductive health problem or a widespread health concern. Yet, too many women cannot identify an abnormality in their cycle because they have no idea how their body functions. So it’s time to change that! #bodyliteracy
You are born with all of the eggs you’ll ever have. Somewhere around two million at birth; down to approximately 150,000 per ovary by the time puberty arrives. New eggs are not created each month. Instead, at the beginning of each cycle, multiple egg-containing follicles begin to mature on your ovary as a response to the follicle stimulating hormone (FSH) being produced by the anterior pituitary gland (located in your brain).
Around day 7, one follicle continues to mature while the others are absorbed back in to the ovary. Soon after, estrogen begins to rise, causing build up of uterine lining and production of cervical mucus.
*This is why certain methods of NFP are based around cervical mucus observations. Cervical mucus production is directly correlated to estrogen levels!*
Cervical mucus is needed for sperm to survive. Without healthy mucus, sperm quickly dies. However, in the presence of hospitable mucus, sperm can live 3-5 days. The human race wants to continue to exist, so our bodies are primed to procreate. Ovulation is a sign of health because it means a woman’s body is working exactly as it should.
After the follicle has been maturing and the estrogen rising, a third hormone surges. Lutenizing hormone (LH) causes the follicle to release the egg, and ovulation occurs. After being released, the egg only lives 12-24 hours. This is why it is important for sperm to have healthy cervical mucus and live for 3-5 days. Otherwise the timing to conceive would be extremely limited and challenging. This is also the basis of NFP: couples have a combined fertility of approximately 6 days. There are external markers of fertility that can be used to identify these days of combined fertility.
Once ovulation has occurred, progesterone is produced (its presence actually confirms ovulation). Progesterone helps the uterus continue to prepare for implantation in the event the egg was fertilized.
Progesterone rise causes a temperature rise in a woman’s basal body temperature. This is why some NFP methods incorporate body temperature. It is another scientifically-backed indicator that ovulation has occurred. As technology has improved, methods like Marquette Model have emerged to objectively identify, through urine metabolites, specific hormones as they rise. This accurately indicates where a woman is at in her cycle.
After 7-10 days, if fertilization has not occurred, progesterone and estrogen levels fall causing the uterine lining to shed. This shedding results in a menstrual period, and a new cycle begins.
The first day of bleeding (not just spotting) is day 1 of the new cycle. You can determine cycle length by counting from day 1 of one cycle to day 1 of the next.
Fun fact: The luteal (post-ovulation) phase is relatively constant. If a woman does not have an underlying hormone or disease process, the number of days from ovulation to the start of her next period should be close to the same each cycle. 12-14 days is the expected length, but as with anything in medicine, individual situations can vary.
Variation in overall cycle length due to stress, illness, medication, and a variety of other factors, results from length fluctuations in the pre-ovulation (follicular) phase. Once ovulation occurs in a healthy cycle, a period will follow in a predictable fashion.
Building off this basic understanding of hormone shifts within the menstrual cycle, this “Body Literacy Series” will delve in to mental health effects of hormone changes, disease processes that affect healthy hormone production, how to correct hormone imbalances, and what changes as we approach menopause or transition back to fertility after a baby.
St. Thomas Aquinas said, "Love follows knowledge." The world will change, for the better, as women understand and love their bodies.