Your Menstrual Cycle: What Happens in the Follicular Phase?

The follicular phase technically kicks off with your period, but it’s easier to separate it from your period flow. 

During this phase, follicle-stimulating hormone (FSH) helps follicles grow.

People assigned female at birth are born with millions of follicles. Follicles are sacs holding immature eggs.

Each cycle, a few of these follicles are chosen to grow, and one becomes the main follicle–dominant follicle–that releases an egg during ovulation.

The other follicles sort of break down through a process called atresia.

FSH is produced in response to gonadotropin-releasing hormone (GnRH) from the hypothalamus in the brain. This increase starts to happen in the previous cycle when the body realizes that pregnancy didn’t occur.

As FSH increases in the new menstrual cycle, estrogen levels rise as well.

Estrogen supports FSH and stimulates the growth of the uterine lining, prepping it for a potential fertilized egg. Estrogen also tells the cervix to make more mucus.

clipart phone with a blue background and white dots representing the days of the month with one week marked in red. There's a clipart woman in front of the phone pointing to it and period products scattered across the background

What about cervical mucus?

The cervix has many glands that produce mucus. This mucus is made up of proteins, electrolytes, sugars, fatty acids, and enzymes. Cervical mucus production is normal and indicates healthy estrogen levels leading up to ovulation.

There’s no “correct” amount of mucus to be made; it varies from person to person. It can offer clues about hormonal changes, especially if accompanied by changes in libido, mood, energy, and vaginal health.

Hormonal conditions and some medications, like antihistamines, can affect mucus production. Life stages with low estrogen, like breastfeeding or menopause, also impact mucus as well.

Cervical mucus can be white, off-white, or clear, changing throughout the cycle due to hormone shifts.

Typically, there’s little to no mucus right after a period, especially with a longer follicular phase. As ovulation nears and estrogen levels rise, mucus production increases, becoming more slippery, stretchy, and alkaline to help sperm travel and survive—this is known as fertile cervical mucus.

It’s normal for cervical mucus to have a slight smell as it passes through the vaginal tract, mixing with sweat, sebum, and other fluids. This isn’t a bad smell, just distinct. However, a fishy or foul odor, especially with yellow, green, or crumbly discharge and symptoms like itching, burning, or pain, might indicate an infection and should be checked by a doctor.

The follicular phase ends with a steady rise in estrogen which leads to a spike in LH that triggers ovulation.