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Understanding Your Menstrual Cycle

Really understanding your menstrual cycle is super important if you are trying to conceive (TTC) or even thinking about TTC. Why? Within your menstrual cycle is a window in which you are most likely to get pregnant, and knowing the different menstrual cycle phases can help you determine the best time to have sex. So, let’s take a closer look at a topic you probably haven’t really thought about since your high school health class.

First, what is the menstrual cycle?

Your menstrual cycle is a group of hormonal cyclical changes that prepare your body for a possible pregnancy.1 It includes the time from the first day of your period all the way to the day before your next period starts. A big misconception is the belief that most women have a 28-day cycle every month. In a 2020 study of anonymized data collected from the Clearblue® Connected Ovulation Test System of more than 32,000 women representing more than 75,000 cycles, 25.3% of users described their cycle length as 28 days, but only 12.4% of users actually had a 28-day cycle.2 Most women (87%) had cycles ranging from 23 to 35 days, and 52% of women had cycles that varied by five days or more in length. Your cycle length impacts the timing of ovulation.2

What happens during the menstrual cycle?

At the start of your menstrual cycle, you begin your period. Once your period ends you enter the follicular phase, followed by ovulation and then the luteal phase of your menstrual cycle. Knowing what happens during each phase of your menstrual cycle is key to understanding the links between menstruation, ovulation and conception, which can help when TTC.

Menstrual cycle phases: Day 1 of your menstrual cycle

This is the first day of your period, also known as menstruation.1 Your body begins breaking down the lining of your uterus.1 Bleeding typically lasts three to seven days, and it’s common to have cramps and pain in your lower abdomen and lower back, especially early on.3 During menstruation, your body is already starting to prepare for ovulation. Your pituitary gland, located in your brain, produces FSH (follicle-stimulating hormone), which kicks your ovaries into gear.4 Fluid-filled follicles develop on your ovaries.4 Each follicle contains one egg.4

Menstrual cycle phases: The follicular phase of the menstrual cycle

During a typical follicular phase, only one follicle keeps growing and starts to release increased levels of estrogen.4 Usually by day eight, you’re feeling pretty good, partly because estrogen increases endorphins and partly because your period is over.3,4 But that estrogen is doing more than affecting your mood. It’s also alerting your uterus, essentially saying, “Hey, we may need you!” In response, the uterine lining becomes thick with nutrients and blood, ready to receive a fertilized egg.3

Menstrual cycle phases: The ovulation phase

You are most fertile in the days leading up to ovulation and the day of ovulation. Pregnancy is most likely to happen when sex takes place in the three days before ovulation. Your estrogen levels might be sky-high right now, which triggers an LH (luteinizing hormone) surge.4 This surge forces your follicle to rupture and release its egg, sending it through your fallopian tube.4 This is ovulation. Your egg will only be viable for up to 24 hours, but — and this is important — sperm can live inside you for up to five days.5 If you have sex on the day you ovulate or a few days prior to ovulation, the sperm just hangs out, waiting for an egg. This is why timing is so important. If the egg and sperm rendezvous, pregnancy is possible.

Menstrual cycle phases: The luteal phase of the menstrual cycle

After you ovulate, your body enters what we call the luteal phase. Your follicle changes into a corpus luteum — a temporary gland that begins making more progesterone, a hormone that helps the lining of your uterus store even more blood and nutrients, just in case it receives a fertilized egg.3 For successful conception to occur, the fertilized egg must continue traveling through the fallopian tube and then attach itself to your uterine lining, about a week after fertilization.3 The fertilized egg implants and starts producing the hCG (human chorionic gonadotropin) hormone, which keeps your estrogen and progesterone levels high, preventing the uterine lining from shedding until the placenta is ready to take over.6

If you’re not pregnant there is no hCG, so your estrogen and progesterone levels drop, which does two things: the thick uterine lining begins to break down and you may experience PMS (premenstrual syndrome).1,3 That unfertilized egg? It breaks apart and leaves your body along with the blood and tissue from your uterine lining.3 Once bleeding starts, you’re back at day one of your cycle.3

Menstruation cycles and pregnancy

Tracking your menstrual cycle is an easy way to help understand your fertility when TTC. Integrating ovulation tests into your fertility tracking can further enhance this understanding. For example, the Clearblue® Advanced Digital Ovulation Test is designed to identify 4 or more fertile days in each cycle, offering a wider window for predicting ovulation.7 Before you use an ovulation test, it’s helpful to know the day your last period started. This calculator can help. Better understanding of your menstruation cycle is an easy tool to add to your kit of tricks and tips when trying to get pregnant.


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Disclaimers & Sources:

  1. Office on Women’s Health, U.S. Department of Health & Human Services. Trying to conceive. Updated February 22, 2021. Accessed January 2, 2024. https://www.womenshealth.gov/menstrual-cycle/your-menstrual-cycle
  2. Soumpasis I, Grace B, Johnson S. Real-life insights on menstrual cycles and ovulation using big data. Human reproduction open. 2020;(2), hoaa011. https://doi.org/10.1093/hropen/hoaa011. Updated April 16, 2020. Accessed January 2, 2024.
  3. Cleveland Clinic. Menstrual cycle. Updated December 9, 2022. Accessed January 2, 2024. https://my.clevelandclinic.org/health/articles/10132-menstrual-cycle
  4. Cleveland Clinic. Follicle-stimulating hormone (FSH). Updated January 23, 2023. Accessed January 2, 2024. https://my.clevelandclinic.org/health/articles/24638-follicle-stimulating- hormone-fsh
  5. Mayo Clinic. Getting pregnant. Updated December 11, 2021. Accessed January 2, 2024. https://www.mayoclinic.org/healthy-lifestyle/getting-pregnant/in-depth/how-to-get- pregnant/art-20047611
  6. Cleveland Clinic. Human chorionic gonadotropin. Updated March 11, 2022. Accessed January 2, 2024. https://my.clevelandclinic.org/health/articles/22489-human-chorionic-gonadotropin
  7. In a study of 87 women, 4 or more fertile days were identified in 80% of cycles using actual cycle length (2012).

Can I get pregnant during my period?

Although it's unlikely, there is still a small chance you can conceive.