Sex Ed: What You Should Know About the Menstrual Cycle

When was the last time you really thought about the menstrual cycle? Our guess is high school sex ed or health class—at least until fertility became a struggle. The fact is, the menstrual cycle, which is far more than just a monthly period, plays an important part in fertility for people with uteruses.

Understanding the different phases of the menstrual cycle and knowing where you are in yours can be helpful in many ways. During your initial consultation at Arizona Center for Reproductive Endocrinology & Infertility, we’ll ask about your medical history, which includes information about your menstrual cycle, as irregularities can be a sign of a reproductive health condition that can hinder a pregnancy, like polycystic ovary syndrome (PCOS). Tracking your cycle is also important when it comes to insemination and similar procedures.

For that reason, here’s what you should know about the menstrual cycle—from its purpose to phases.

The Basics

The main purpose of the menstrual cycle is to prepare the body—specifically the uterus—for the possibility of pregnancy. Each month, follicles in the ovaries are stimulated, an ovary releases an egg, and the menstrual cycle begins. Once the last phase of the cycle ends, the first one begins again, and the cycle continues—until a pregnancy occurs or until menopause (which is the end of the menstrual cycle).

The menstrual cycle can last between 24 to 38 days, with an average length of 28 days. And it can be impacted by several factors, including age, lifestyle, health conditions, and hormonal birth control.

The Phases

Menstrual cycles can be broken into four phases: the follicular phase, ovulation, the luteal phase, and the menstrual phase.

The Follicular Phase

The follicular phase starts on the first day of your period and ends with ovulation—around 14 or 15 days later (based on a typical cycle). During this phase, the pituitary gland releases two hormones, follicle stimulating hormone (FSH) and luteinizing hormone (LH). These hormones stimulate the ovary to produce around five to 20 follicles; the first one matured is then released as an egg, or ovum. The immature follicles that haven’t developed enough for ovulation are reabsorbed and die off. While this is all happening, the body’s levels of estrogen increase, which prompts the uterine lining to thicken in preparation for implantation.


Ovulation is the next phase, and only lasts one day. This is when one of the ovaries releases a matured egg for possible fertilization; then fimbriae, which are finger-like tendrils along the fallopian tubes, move the egg through the tube and into the uterus. The five days leading up to and the day of ovulation are considered your “fertile window,” when chances for conception are the highest.

The Luteal Phase

The last phase of the cycle is the luteal, or secretory, phase—which lasts about 14 days. In this phase, the ruptured follicle (that released the egg during ovulation) transforms into the corpus luteum, which increases progesterone levels and thickens the uterine lining to make it a receptive home for a fertilized egg to implant itself. If pregnancy does occur, the corpus luteum will continue to produce progesterone and the implanted embryo will begin to produce human chorionic gonadotropin (hCG), which is what pregnancy tests use to determine a pregnancy. However, if fertilization does not occur during this phase, then progesterone levels will fall again and your period will start.

The Menstrual Phase

This is the time of your cycle when your period, or menses, occurs; this phase typically lasts four to seven days. Your period is a visual marker that helps you distinguish the beginning and end of ovulation. When you have your period, estrogen and progesterone levels decrease and your body sheds the uterine lining that was created during the previous cycle.

If you have any questions about your menstrual cycle, we are here to answer them! We want you to feel knowledgeable and confident in what’s happening in your body, and how it may be affecting your fertility. You can make an appointment for a consultation by calling us at 520-326-0001 or visiting us online.



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