What Your Menstrual Cycle Can Tell You About Fertility

Anita A. Galdieri, PharmD, RPh Disclosures Published on Jun 2, 2023

This article is for people who are interested in becoming pregnant and their partners, or anyone who wants to learn more about the menstrual cycle and fertility (ability to get pregnant). The goal of this activity is to help you talk to and work with your doctor and healthcare team about your menstrual cycle and any fertility concerns.

You will learn about:

What the menstrual cycle is and what happens during its phases
Roles of main hormones during the menstrual cycle
What "abnormal" or "irregular" means regarding menstrual cycles
Hormones and fertility
Talking to your doctor and healthcare team, and questions you can ask

Test Your Knowledge

What Is the Menstrual Cycle?

Your menstrual cycle is a series of changes your body goes through every month to prepare for a possible pregnancy. Each month, a mature egg is released by an ovary -- this is called ovulation -- and moves down the fallopian tube where it can potentially be fertilized.

At the same time, the lining of your uterus (your endometrium) builds up so the egg can take hold there if it becomes fertilized. If it isn’t fertilized, your endometrium sheds and the tissue and blood pass through your cervix and vagina out of your body. This is your period or menstruation.

Each menstrual cycle starts on the first day of your period and ends the day before your next period.

Roles of Main Hormones During Your Cycle

Your menstrual cycle is primarily controlled by 4 main hormones:

Follicle-stimulating hormone (FSH) that helps the egg mature. It also stimulates estrogen and progesterone production
Luteinizing hormone (LH) that surges to cause ovulation. It also stimulates estrogen and progesterone production
Estrogen that increases LH to lead to the LH surge. It also helps prepare the endometrium for a possible pregnancy
Progesterone that helps prepare the endometrium for a possible pregnancy

Hormone Levels During Menstrual Cycle Phases

Your menstrual cycle hormones will interact and go through important changes during each phase:

Follicular phase: FSH increases. Estrogen and progesterone are low, causing the endometrium to shed (the first day of your cycle)
Ovulatory phase: Estrogen increases, helping the LH surge. Estrogen then goes down while progesterone goes up
Luteal phase: FSH and LH go back down. Estrogen increases again and, along with progesterone, helps build up your endometrium. If an egg is not fertilized, progesterone and estrogen decrease and the next menstrual cycle starts

What Does "Irregular" Mean?

The average menstrual cycle is 28 days long. But for many people it can be as short as 21 days or as long as 38 and still be considered regular. For some, their cycles are so regular they can predict the day their period will start.

But a menstrual cycle may be considered "abnormal" or "irregular" when the number of days between periods is different some months. Having irregular cycles, no periods, or abnormal bleeding may mean you aren't ovulating and can affect your fertility. This is because ovulation is the part of the cycle when pregnancy can happen. Certain health conditions can also lead to irregular cycles, missed periods, or abnormal bleeding and affect your health or fertility.

Hormones and Your Fertility

The levels of your menstrual cycle hormones can impact your fertility. For example, if estrogen levels are too high or too low, it can change your fertility. And too little progesterone can interfere with preparing the endometrium for a possible pregnancy.

If estradiol -- another hormone and a form of estrogen -- is too low, it can also affect your menstrual cycle and fertility. Too much estradiol can affect fertility and impact certain health conditions that affect fertility.

Irregularities or Changes to Look For

There may be a problem with your menstrual cycle if:

Your periods were regular and then became irregular
Your periods are less than 21 days apart, or more than 38 days apart
Your periods happen more than 90 days apart, even for 1 just cycle
You've missed 3 or more periods in a row and you're not pregnant
Your period lasts for more than 7 days
You're bleeding more heavily than usual or soak through a pad or tampon every 1-2 hours
You have severe pain, nausea, or vomiting during your period

Talking To Your Doctor

Changes or irregularities can be fairly common and many people can have slight variations in their cycle length. To track your cycle, you can use a calendar to record the day your period starts every month. This can help you know when you ovulate, are most likely to get pregnant, and when your next period should start.

Understanding your menstrual cycle and talking to your doctor about any irregularities can be important for your health and your fertility. Menstrual cycles can be different for different people, so your doctor or healthcare team member can help you understand what's normal or regular for you, talk to you about your fertility, and check for any health conditions if you are having problems.