What is an anovulatory cycle and why does it occur?

Anovulation is when the egg (or oocyte) is not released from the ovary, and it is responsible for nearly 30% of fertility problems in women (1). It has been identified in 3.4% to 18.6% of menstruating women, making it a quite common condition (2). Irregular periods (shorter than 21 days or longer than 35 days) or lack of a period can be signs of anovulation (3). Technically you cannot menstruate without ovulating, since menstruation refers to the normal vaginal bleeding that occurs when the lining of the uterus sheds because an egg was released but not fertilized. However, you might have experienced an anovulatory cycle without noticing, because bleeding can still occur without ovulation, a condition called abnormal uterine bleeding (AUB), which can be confused with a normal period (4).

But, why does it happen? This question is not easy to answer, since anovulation can involve a lot of organs, glands, and hormones. It is believed that the cause of AUB is a disturbance in the hypothalamic-pituitary-ovarian axis (2). Conditions such as Polycystic ovarian syndrome (PCOS), premature ovarian insufficiency (POI), hypothalamus or pituitary gland dysfunction, and menopause, are associated with AUB (5). Nevertheless, anovulatory cycles are also common in girls that are just starting to menstruate, or in women that have too high or too low body weight, exercise a lot, don’t nourish their bodies properly and/or have high levels of stress (6). This reflects that lifestyle habits can have a big impact on ovulation, even in women that have regular cycles. Also, medications like antiepileptics and antipsychotics are also associated with AUB.

The gold standard for the identification of anovulatory cycles is a transvaginal ultrasound, however this is a resource intensive procedure that involves daily, mid-cycle ultrasound scans (1). Depending on the case and medical history, the doctor may check the levels in blood of progesterone, thyroid hormones, prolactin, LH and FSH (4).

Identifying the root of the hormone imbalance, as well as if the patient wants or not to have a baby, are essential to determine the right treatment. Can be from increasing the food quantity and quality, managing stress or medications to treat ovulatory dysfunction (4).

Tracking and charting your hormones is very important to identify if ovulation happened or not, especially if you’re trying to get pregnant. You can do this with basal temperature charts or with ovulation tests, such as the Pearl’s PdG ovulation test.

References: 1.Lynch, K. E., Mumford, S. L., Schliep, K. C., Whitcomb, B. W., Zarek, S. M., Pollack, A. Z., Bertone-Johnson, E. R., Danaher, M., Wactawski-Wende, J., Gaskins, A. J., & Schisterman, E. F. (2014). Assessment of anovulation in eumenorrheic women: comparison of ovulation detection algorithms. Fertility and sterility, 102(2), 511–518.e2. https://doi.org/10.1016/j.fertnstert.2014.04.035 2.Jones K, Sung S. Anovulatory Bleeding. [Updated 2021 Dec 12]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK549773/ 3.https://www.osmosis.org/answers/anovulatory-cycle#:~:text=Menstrual%20bleeding%20that%20is%20lighter,occur%20without%20any%20noticeable%20signs. 4.https://my.clevelandclinic.org/health/diseases/21698-anovulation#:~:text=What%20is%20anovulation%3F,a%20common%20cause%20of%20infertility. 5.https://www.webmd.com/infertility-and-reproduction/what-is-anovulation 6.https://www.healthline.com/health/pregnancy/anovulatory-cycle#causes