Follicular Phase of the Menstrual Cycle
The follicular phase of the menstrual cycle (or menses cycle) represents the first half of your menstrual cycle. It occurs in the ovaries and lasts approximately two weeks. The first 5 to 7 days of the follicular phase also coincide with menstruation.
The 4 Phases of the Menstrual Cycle
To understand the follicular phase, it’s important to know how it fits within the menstrual cycle as a whole. The 4 stages of the menstrual cycle are:
Menstruation: Menstruation (more commonly referred to as your period) kicks off the menstrual cycle. The first day of your period represents day 1 of your cycle. Menstruation only happens if the egg from the previous cycle has not been fertilized.
Follicular Phase: The follicular phase of your cycle also begins on the first day of your menstrual cycle and lasts approximately 14 days. During this phase, follicles form on the ovary, one of which will eventually release an egg in the next phase.
Ovulation: On approximately day 14-16, one of the eggs produced during the follicular phase matures to an oocyte and is released into the fallopian tube where it sits for about 12-48 hours waiting to be fertilized.
Luteal Phase: The luteal phase of the menstrual cycle occurs after ovulation and lasts approximately 12-14 days. What happens during this phase depends on whether or not the egg is fertilized.
The average menstrual cycle is 28-days long; however, many women experience cycles as short as 21 days or as long as 35 days. The timeline of the average menstrual cycle look like this:
For now, let’s focus on the follicular phase, what’s happening in your body during this time, and potential complications to look out for.
What Happens During the Follicular Phase of the Menstrual Cycle
Both the follicular phase and the menstrual phase start on the first day of your menstrual cycle (day 1). The end of this phase is marked by the ovulation phase, approximately 14-15 days into the average cycle.
Although the follicular phase and menstrual phase overlap for the first 5-7 days of your cycle, there are distinct differences. The key differentiator between these two phases is their location. Menstruation happens in your uterus whereas the follicular phase occurs in the ovaries. The role of hormones also sets the two phases apart.
The Follicular Phase and Hormones
The main hormone driving the follicular phase is follicle-stimulating hormone (FSH), released by the pituitary gland. At the start, progesterone and estrogen levels are low; however, levels rise later in this phase.
Your pituitary gland releases follicle-stimulating hormone (FSH) which causes a cluster of ovarian follicles to collect on the ovary’s surface. About 5-20 tiny follicles (or pods) will form, each containing a single egg.
At that point, the dominant follicle will yield the healthiest and strongest egg, which will mature into an oocyte that will be released in the next phase (ovulation). The ruptured dominant follicle that’s left behind will become the corpus luteum in the next phase.
The clustered follicles trigger a surge in estrogen levels that stimulates the uterine lining and cause it to thicken in preparation for a possible pregnancy.
Follicular Phase Length: Around 14 Days
The average follicular phase lasts around 14-15 days. Having said that, some women may experience this stage being as short as 12 days or as long as 18 days. According to the Journal of Women’s Health, there are many factors that can cause the follicular phase to be longer or shorter. For example:
- The birth control pill
- Marijuana use
Anything less than 12 days is considered short and anything longer than 18 is considered long. A short or long follicular 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?
Since an egg needs time to mature and ripen, a short follicular phase (11 days or less) can prevent that from happening. Without a mature egg, fertilization is a lot more difficult to achieve.
A shorter follicular phase is a very common thing to experience as you age. As women approach their late 30s, hormone levels change and their ovaries begin to age naturally. Although levels of follicle-stimulating hormone (FSH) remain the same, luteinizing hormone (LH) levels tend to drop, causing follicles to rupture before the egg is ready to be fertilized.
This is one of the main causes of a short follicular phase in women over 35. As mentioned, it’s totally normal and no cause for concern, unless you’re planning to get pregnant at the time. If this is the case, you may want to seek medical advice to discuss fertility treatments that can help boost your chances of getting pregnant.
According to the Mayo Clinic, in vitro fertilization is the primary treatment for women over 40 who are struggling to get pregnant.
What Does a Longer Follicular Phase Mean?
A long follicular phase (over 19 days) results when it takes the follicle a particularly long time to mature and release an egg. When the follicular phase is longer, it has a domino effect on the menstrual cycle as a whole and will cause your entire cycle to be longer than average.
A long follicular phase is not strongly associated with any fertility issues. It simply means your body is taking a bit longer to ovulate, so getting pregnant may take a little longer.
The main causes of a longer follicular phase are unclear; however, a study by The Journal of Gynecology and Endocrinology found that women with a long history of taking the birth control pill experienced a long follicular phase in the months immediately after they stopped taking it.
Follicular Phase Symptoms
What happens in the ovaries during the follicular phase is typically unobserved. It’s a very different story in the uterus, at least during the first half of the follicular phase (also known as menstruation).
Some tell-tale signs of menstruation include bloating, abdominal cramps, and mood swings. Though there are no obvious signs signalling the follicular phase, the much more obvious signs of menstruation will tip you off when you're entering your follicular phase as well.
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:
Day 1-8: It’s very difficult to get pregnant during this period of time. Since menstruation also happens during this window, it’s highly unlikely for an egg to be present.
Day 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 vagina for up to 5 days after sex. Since ovulation (your most fertile phase) comes next, if you have sex within 5 days of the egg being released, there is a good possibility a sperm can fertilize it.
What’s My Temperature During the Follicular Phase?
Your basal body temperature fluctuates throughout your menstrual cycle. According to Planned Parenthood, most people have a basal body temperature of about 96-98 degrees Fahrenheit right before ovulation.
Measuring basal body temperature is a common form of fertility awareness women use to get pregnant. To try the temperature method, take your temperature first thing in the morning and track it over several 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
- Pain or a burning sensation when peeing
- Unusual vaginal discharge
- Red and itchy vagina
Regardless of your cycle, always seek medical advice if:
- You suspect you’re pregnant
- You experience inconsistent spotting on a regular basis
- You bleed or spot after unprotected sex
- You notice post-menopausal vaginal bleeding
A Note on the Proliferative Phase
The proliferative phase occurs in the uterus just after menstruation and overlaps with the second half of the follicular phase. The maturing ovarian follicles release estrogen and estradiol (another form of estrogen). Estradiol triggers new layers of endometrial growth in the uterus to prepare the body for the possibility of pregnancy. (Source)
The cervix also goes through changes during the proliferative phase. It becomes more dilated and can produce a thin, liquidy discharge. This is all in an attempt to make the vagina less acidic and more sperm-friendly.
The proliferative phase is the second of three phases of the uterine cycle. It happens right after menstruation and right before the secretory phase.