What are follicles in IVF?

What are follicles in IVF?

A growing egg is housed in a tiny sac of fluid called a follicle in the ovaries. At the start of puberty, females have between 300,000 and 400,000 eggs. A certain number of follicles, each holding an egg, are chosen to develop and grow during each monthly menstrual cycle. The majority of these follicles, meanwhile, do not mature and eventually vanish.

What is a follicle?

A follicle is chosen and continues to develop each month. This follicle bursts and releases the egg, which is now prepared for fertilization, after it has reached maturity and the proper size. Typically, this occurs 14 days after the beginning of the menstrual cycle. Hormones released by follicles start various menstrual cycle phases. (1)

What are the methods applied to make enough follicles and eggs?

To “pump” the ovaries into producing enough follicles and eggs, several ovarian stimulation medication programs are employed. Without stimulant medications, the ovaries only produce and release one mature egg per menstrual cycle (month). Popularly used stimulation regimens involve injections of follicle-stimulating hormone (FSH).

  • Luteal Lupron protocol also known as “long Lupron”, or agonist “down-regulation”
  • Antagonist protocols that contain using the GnRH antagonist medications
  • Flare and micro-flare protocols, also called short Lupron protocols, or short protocols are used for patients who are expected to have a low response to ovarian stimulation. (2)

Why is follicle count crucial for IVF? 

Knowing the number of follicles present is crucial during various forms of fertility treatment so that medical professionals can gauge your potential response to various treatment approaches. 

Your ovaries are induced to create several mature follicles at once in preparation for an IVF cycle in Turkey. Between 10 and 15 follicles are the number that doctors focus on. 

It’s possible that not every follicle has a mature, healthy egg when the eggs are sucked from the follicles with a fine needle. Therefore, if the final number of eggs available for fertilization is less than the number of follicles you initially have, you shouldn’t be too shocked. (3)

How IVF Stimulation Is Performed? 

  • The woman is initially cautioned by the doctors to harvest at least 4 follicles with a diameter of 14 to 20 mm. 
  • The ideal number of follicles ranges from 8 to 13, between 13 and 20 mm. 
  • The objective is to obtain a sizable number (about 8–15) of high-quality eggs. 
  • Monitoring is done of the developing follicle sizes and blood hormone levels. 
  • Using ultrasound, follicle size is determined (discussed above on this page) 
  • Blood levels of the hormone estrogen are crucial. At the beginning of the cycle, estrogen (or estradiol) levels are typically lower than 60 pg/ml, and they significantly increase as more follicles grow. 
  • Estradiol levels typically peak between 1000 and 4000 pg/ml during final trigger with hCG in IVF. 
  • Typically, the stimulating phase lasts 8 to 10 days. (4)

How can I increase my follicle count?

Women gradually lose a fraction of their total egg reserve each month. It’s commonly believed that this loss is due to the ovulation of an egg, but in reality, a group of follicles containing potential eggs undergoes cell death and atresia if not chosen for ovulation. Therefore, even though women are not ovulating due to conditions such as polycystic ovarian syndrome (PCOS) or taking oral birth control, their egg count still decreases with time. After puberty, about one thousand eggs are lost every month until menopause.

Several factors can affect follicle count, such as age, genetics, and certain medical conditions. However, some lifestyle changes may help improve your chances of slowing the pace of  follicle loss. You should follow a healthy diet, exercise regularly, manage your stress, and avoid smoking and excessive alcohol consumption.  

It’s important to note that while lifestyle changes may help improve follicle count, they may not always be effective in increasing fertility. If you are struggling with fertility issues, it’s important to talk to your doctor or a fertility specialist for personalized advice and treatment options.

How many follicles are required for IVF pregnancy? 

Obtaining sufficient follicles for growth is typically not difficult. However, occasionally the ovaries don’t respond well and there aren’t many follicles that are growing. The minimal number of follicles needed to proceed with IVF if the number of eggs retrieved is low varies on a variety of variables, including their size, the woman’s age, the outcomes of prior stimulations, and the willingness of the couple to continue egg collecting.

The bare minimum of follicles needed to proceed with IVF depends on a variety of factors including their size, the woman’s age, the outcomes of earlier simulations, and the willingness of the couple (and doctor) to continue egg collection.

Others can perform the egg retrieval with just one follicle, while some specialists insist that there should be at least five that are 14mm or greater. The majority of IVF clinics in the US demand at least three to four mature (or nearly mature) follicles. 

Women with llow basal antral follicle counts, those older than about 37, those with high FSH levels, and those who exhibit other symptoms of diminished ovarian reserve are more likely to respond poorly to ovarian stimulation. (5)


Vaiarelli, A., Cimadomo, D., Ubaldi, N., Rienzi, L., & Ubaldi, F. M. (2018). What is new in the management of poor ovarian response in IVF?. Current Opinion in Obstetrics and Gynecology, 30(3), 155-162.

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