The follicular phase is the time of the month when you get your period and your ovaries prepare an egg for ovulation. Here’s more about what exactly is happening in your body during the follicular phase, and what it all means for pregnancy.
Your menstrual cycle is made up of two phases: the follicular phase and the luteal phase .
Throughout each phase, changing hormone levels trigger different functions as your body busily prepares for a potential pregnancy. Then, it starts the cycle over again if you don’t get pregnant.
The follicular phase starts on the first day of your period and lasts until you ovulate. During the follicular phase, your body prepares a follicle (an immature egg) to be released during ovulation.
Here’s a closer look at what’s happening with your body during the follicular phase, how long this phase may last, signs you’re in this phase, and whether you can get pregnant during the follicular phase.
What is the follicular phase? The follicular phase, sometimes called the “proliferative phase,” is one of the two phases of your menstrual cycle. The follicular phase starts on the first day of your period , also known as day one of your cycle, and lasts until you ovulate.
During the follicular phase, a few different things are happening in your body, mostly revolving around your ovaries and eggs:
You get your period Your ovaries produce follicles An egg matures and prepares to be released during ovulation Your uterine lining (or endometrium) thickens You get your period Your period is the sign that your menstrual cycle has restarted, and it’s also the sign that your follicular phase has begun. During your period, you shed the lining of your uterus, which was thickened during your previous menstrual cycle in preparation for a potential pregnancy. Your follicular phase continues past the last day of your period.
Your ovaries produce follicles At the same time as your period, the hypothalamus and the pituitary gland—two structures in your brain that are crucial to hormone production—get involved. Your hypothalamus sends a signal to your pituitary gland to begin producing follicle-stimulating hormone (FSH). In response to rising FSH levels, your ovaries start producing follicles—pretty straightforward, given the name “follicle-stimulating hormone.” Each follicle houses an immature egg, which grows as the follicular phase continues.
An egg matures and prepares to be released during ovulation Soon, one follicle becomes the dominant follicle. The other follicles start to deteriorate and are eventually reabsorbed back into your body. In the dominant follicle, meanwhile, an egg continues maturing until it reaches full maturity.
Your uterine lining (or endometrium) thickens The maturing egg releases estrogen, making overall estrogen levels rise. Rising estrogen stimulates your uterine lining to grow thick and rich in nutrients. A thickened endometrium is necessary for a fertilized egg to be able to implant in the uterus and for pregnancy to occur.
These rising estrogen levels also send signals to your hypothalamus and your pituitary gland to decrease FSH levels and increase luteinizing hormone (LH) levels , a hormone crucial to ovulation.
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When LH surges (meaning hits its peak level), ovulation is triggered, the mature egg is released from its follicle, and the follicular phase ends. Ovulation marks the start of the luteal phase, the next phase of your cycle.
How long is the follicular phase? Just like your cycle length, the length of your follicular phase can vary, too—from person to person and from month to month.
The length of your follicular phase is determined by how long it takes for a given follicle to mature into an egg.
When the maturing process takes longer, the follicular phase is longer and your cycle is longer. On the flip side, the follicular phase, and your cycle, are shorter when it takes less time for a follicle to mature. The length of your follicular phase also changes with age.
Cycles can be anything from 21 to 35 days long and still fall within a normal range, and the follicular phase varies along with that. The follicular phase can range from 10 to 16 days .
Keep in mind that follicular phase length changes, meaning it’s entirely possible to have short, long, and mid-range follicular phases from one cycle to the next.
What does it mean if the follicular phase is long? If your follicular phase lasts longer than 16 days, it can be considered long. This doesn’t necessarily mean much, aside from the fact that your overall cycle is long, too.
Your follicular phase may be longer if you’ve used birth control pills for a long time, or if you were on the pill recently.
If your follicular phase is longer, it doesn’t impact your fertility or mean that you’re less likely to become pregnant.
What does it mean if the follicular phase is short? If your follicular phase lasts less than 10 days, it’s considered short.
When the follicular phase is short, the egg released during ovulation may not have had enough time to fully mature , which also means it may not be able to be fertilized by sperm. This can impact the chances of conceiving in a given cycle, or overall if your follicular phases are consistently short.
In other words, a shorter follicular phase may make it harder for you to get pregnant.
A shorter follicular phase may also be a sign that you’re entering perimenopause , or the transition into menopause, as the follicular phase shortens near menopause.
How do you know if you’re in the follicular phase? There are a few ways to know that you’re in the follicular phase of your cycle.
Follicular phase symptoms The most telltale sign of this phase is your period. During the follicular phase, you may experience symptoms typically associated with your period, like:
Bloating Cramps Nausea Breast tenderness Lower back pain Headaches Tiredness Mood swings >>RELATED: 8 Symptoms That Could Be Related to Your Period - And How to Get Relief
Basal body temperature
Your basal body temperature (BBT) , or your body temperature when you’re fully at rest, can also indicate which phase of your cycle you’re experiencing. BBT is at its lowest during the follicular phase, typically ranging from 97°F to 98°F. BBT increases following ovulation and the start of the luteal phase.
To track how your BBT changes throughout your cycle, take your temperature in the morning, right when you wake up and before you get out of bed. After a few cycles-worth of daily temperature readings, you may be able to use your BBT to track the phases of your cycle and find when you’re most fertile .
Hormone-based cycle tracking The final and most accurate way to know you’re in your follicular phase is to track your cycle, specifically through changes in your hormones. Regular cycle tracking works on the assumption that you follow a 28-day menstrual cycle, when the reality is that many people don’t fall into that standard—and that’s completely normal!
Instead, by measuring key hormones of the menstrual cycle, like LH, estrogen, and progesterone, you can get a clear picture of when your unique hormone trends and cycle timing. For example, tracking estrogen can help you understand when your body is ready to release the mature egg, and tracking LH can show you when you’re experiencing the LH surge and are about to ovulate.
Can you get pregnant during the follicular phase? Yes, you can get pregnant during the follicular phase.
More specifically, the late follicular phase is the time when you should have sex if you’re trying to conceive, as this part of your cycle corresponds with your fertile window .
Your fertile window is the time during your cycle when you’re most fertile – and most likely to get pregnant. At-home fertility testing kits are one tool to track your cycle phases and find your fertile window. Generally, the fertile window lasts six days : the five days leading up to ovulation, and the day after ovulation.
This timeline means that most of your fertile window occurs during the late follicular phase, making the follicular phase the time in your cycle when you’re most likely to get pregnant.
The follicular phase: the bottom line There’s a lot going on in your body during the follicular phase of your menstrual cycle.
You get your period, your ovaries start producing follicles, a follicle matures into an egg to be released during ovulation, and your endometrium thickens.
The follicular phase can vary in length from cycle to cycle, depending on how long it takes for a follicle to mature. While a longer follicular phase doesn’t impact fertility, a shorter follicular phase may make it harder for you to get pregnant in a given cycle.
If you’re trying to conceive, knowing the signs of the follicular phase and tracking your menstrual cycle can be key for timing when to have sex. When all goes well, the follicular phase may just be the part of your cycle when you’re most likely to get pregnant.
