Follicular Phase of the Menstrual Cycle

The follicular phase of the ovary is when the egg undergoes a maturation process, and this begins on the first day of your period (day 1 of your cycle) and ends with ovulation (approximately day 13-15 of a cycle of 28 days). 

At the same time that the ovary is in its follicular phase, the uterus is in its proliferative phase, which includes reconstruction and regrowth of the endometrium (uterine lining). 

The Phases of the Menstrual Cycle

The menstrual cycle includes 3 different uterine phases that are occurring at the same time as 3 different ovarian phases. It’s not always obvious which phase you're in, with the exception of the menstruation phase (a.k.a. your period). 

1. Menstruation

Menstruation is a phase of the uterus that occurs during the follicular phase of the ovary: More popularly referred to as your period, menstruation (or menses) marks the first day of your cycle. If an egg has not been fertilized, the egg disintegrates, and your uterus sheds the lining it built from the previous month’s menstrual cycle. This is your period.

2. Follicular Phase 

The follicular phase of the ovary is when the egg undergoes a maturation process, and this begins on the first day of your period (day 1 of your cycle) and ends with ovulation (approximately day 13-15 of a cycle of 28 days). 

At the same time that the ovary is in its follicular phase, the uterus is in its menstruation phase (sloughing of the uterine lining and menstrual blood flow), which then transitions into the proliferative phase, which includes reconstruction and regrowth of the endometrium (uterine lining).

3. Ovulation

After the ovarian follicular phase ends, ovulation typically occurs and this is around Days 13-15 of a 28d cycle. The day of ovulation is distinctly defined by the act of the oocyte bursting through the ovarian capsule, out of the ovarian follicle, traveling through the fallopian tube, and becoming available to sperm for fertilization. 

4. Luteal Phase

The luteal phase of the ovary typically lasts for two weeks after ovulation (day 17-28 in a 28d cycle). During this phase, the remnant follicle remodels itself into an enlarged, lipid-rich body known as the corpus luteum. The corpus luteum produces hormones that would be helpful for a developing pregnancy if one were to occur. If no fertilization occurs after 14 days, then the corpus luteum breaks down, which decreases the hormonal production, and menstruation begins. 

During the luteal phase of the ovary, the uterus is in the secretory phase, which means it is using the hormones from the corpus luteum to prioritize the secretion of substances that keep it stable instead of those that cause it to proliferate and grow—all in preparation for implantation of a pregnancy.

The Menstrual Cycle: A Timeline

Your menstrual cycle is sometimes referred to as your monthly cycle. The most commonly referenced menstrual cycle is 28 days. However, the normal range for many adult women of reproductive age is 21–35 days. During this time, your body prepares for the possibility of fertilization and pregnancy. Your period is a sign that pregnancy did not occur.  

For now, let’s explore what is happening during your ovary during the follicular phase,

What Happens During the Follicular Phase of the Menstrual Cycle

The follicular phase occurs to ensure that the proper follicle is ready for ovulation.

As stated above, the follicular phase of the ovary is when the egg undergoes a maturation process, and this begins on the first day of your period (day 1 of your cycle) and ends with ovulation (approximately day 13-15 of a cycle of 28 days). 

At the same time that the ovary is in its follicular phase, the uterus is in its menstruation phase (sloughing of the uterine lining and menstrual blood flow), which then transitions into the proliferative phase, which includes reconstruction and regrowth of the endometrium (uterine lining).

Both the follicular phase and the menstruation phase begin on the first day of your menstrual cycle (Day 1). The end of this phase is marked by the ovulation phase, approximately 13-15 days into a 28-day menstrual cycle. 

Menstruation is the shedding of the lining of the uterus (endometrium) and happens in the uterus, while the follicular phase occurs in the ovaries. 

The Follicular Phase and Hormones

The hormone driving follicular maturation is follicle-stimulating hormone (FSH), which is released by the pituitary gland. At the beginning of the follicular phase, estrogen and progesterone levels are low; however, levels rise throughout this phase.

Follicle-stimulating hormone “recruits” follicles that respond to it and show this response by increasing the size of their eggs and the cuboidal cells around them.

Eventually, a dominant follicle emerges as the follicle that will release the matured egg during ovulation. 

Follicular Phase Length: Around 14 Days

The average follicular phase lasts around 14–15 days. Having said that, some may experience this stage being as short as 12 days or as long as 18 days. The variations in menstrual cycle length are typically variations in the follicular phase length of the ovarian cycle.

According to the Journal of Women’s Health, there are many factors that can cause this stage to be longer or shorter. For example:

• Smoking
• Age
• Birth control pill
• Marijuana use

A short or long phase isn’t necessarily a cause for concern, but, in some cases, a visit to the doctor for some medical advice is advised.

What Does a Short Follicular Phase Mean?

It is common for the follicular phase to shorten and for FSH levels to increase with age. The earlier rise in FSH levels during the follicular phase leads to an earlier rise in estradiol levels which can also lead to an earlier selection of the dominant follicle. Sometimes this can even result in more than one dominant follicle, which can partially explain the higher prevalence of dizygotic twins in older cycling women.

Luteinizing hormone (LH) levels and luteal phase duration remain unchanged.

What Does a Longer Follicular Phase Mean?

As stated above, the variations in menstrual cycle length are typically variations in the follicular phase length of the ovarian cycle, and these are largely normal variations. The largest concern from a fertility standpoint is if ovulation is not achieved.

Frequently Asked Questions About the Follicular Phase of the Menstrual Cycle

Can I Get Pregnant During the Follicular Phase?

While it’s true you are not ovulating during the follicular phase; it’s still possible to get pregnant. The probability of getting pregnant varies depending on where you are in the follicular phase:

• Days 1–8: It’s very difficult to get pregnant during this period of time. Since menstruation also happens during this window, the risk of pregnancy is decreased because the chances of a mature egg being present are low.
• Days 9–13: Your chances of getting pregnant are much higher if you have sex during this time. The main reason for this is that sperm can survive in the female reproductive system for up to 5 days, so if ovulation (your most fertile phase) occurs less than 5 days after intercourse, it is still possible to get pregnant.

What’s My Temperature During the Follicular Phase?

Your basal body temperature fluctuates throughout your menstrual cycle. 

• Lower basal body temperature (this typically occurs just before ovulation begins and an immature egg is released) averages between 97°F (36.1°C) and 97.5°F (36.4°C) before ovulation, according to Healthlink BC.
• Higher basal body temperature (occurs approximately 24 hours after the egg is released and lasts for many days) ranges between 97.6°F (36.4°C) and 98.6°F (37°C) after ovulation, according to Healthlink BC.

Measuring basal body temperature is a common form of fertility awareness women use to track ovulation if trying to conceive. To try the temperature method, take your temperature first thing in the morning and track it over several menstrual cycles. If you’re interested in using this method to track your fertility, consult with your doctor. 

When Should I Seek Medical Advice?

As mentioned, the menstrual cycle phases can vary in length, so a little bit of irregularity is nothing to be concerned about. Having said that, it’s best to seek medical advice if you experience any of the following:

• Heavy periods with large, quarter-sized clots
• Irregular periods
• Spotting between periods along with abdominal pain/cramping that affects the quality of life
• Pain or a burning sensation when peeing
• Unusual vaginal discharge or vulva irritation that is bothersome or affects the quality of life

Regardless of your cycle, always seek medical advice if:

• You suspect you’re pregnant
• You experience inconsistent spotting regularly
• You bleed or spot after unprotected sex
• You notice post-menopausal vaginal/uterine bleeding

A Note on the Proliferative Phase

The proliferative phase includes reconstruction and regrowth of the endometrium (uterine lining) and occurs after menstruation at the same time that the ovary is in the follicular phase.

The estrogen produced by the maturing ovarian follicles triggers endometrial re-growth in. preparation for fertilization and implantation of a potential pregnancy.

The cervix also goes through changes during the proliferative phase. It softens, which is sometimes known as having a short, high, open, and wet cervix (SHOW), and can produce cervical mucus that is wet and stretchy with an egg white texture. This is all in an attempt to make the vagina less acidic and more sperm-friendly.

Medically reviewed by Dr. Chimsom T. Oleka, M.D, Written by Jane Flanagan — Updated on November 1, 2021.

We hope you found this post informative — but remember: we’re not doctors and this post is not medical advice! While all posts are fact-checked and well researched, we always recommend you chat with your doctor about any questions or concerns you might have regarding a medical condition. We’re here to support and educate, but never with the aim of disregarding professional medical advice you’ve been given. Phew, now that that’s out of the way, you can go on living unapologetically free.