• English
Birla Fertility & IVF
Birla Fertility & IVF

Ovarian Follicle Size for Conceiving

  • Published on April 16, 2022
Ovarian Follicle Size for Conceiving

Parenthood is a significant milestone for most Indian married couples. Conception, however, is not always an easy and quick journey for all. Several couples come across a range of challenges while trying to conceive and are overwhelmed with a truckload of questions, starting with a why. ‘Why am I unable to conceive?’ is a common query faced by wishful parents. The path to finding the answer to this question goes through understanding your body. In women, the quest starts with learning about the follicle size for conceiving. 

According to the World Health Organisation (WHO), nearly 48 million couples across the world experience some form of infertility issue each year. However, the data on how many of these couples are seeking active fertility care is steep. It is because of a lack of awareness about the female reproductive system and its functions. 

In this article, we will learn about the minimum egg size to get pregnant with expert insights from Dr. Meenu Vashisht Ahuja, a leading fertility specialist at Birla Fertility & IVF. 

Seeking fertility care can be confusing for some due to its heavy medical terminology. At Birla Fertility & IVF, along with clinically reliable treatments, we inform and educate our patients so that they are aware of their condition and can make wise and informed decisions. 

To find out how the normal size of follicles for pregnancy is relevant, let’s begin by exploring the follicle meaning.

What is Follicle?

An ovarian follicle is a fluid-filled sac containing an immature egg, also known as an oocyte. The development of ovarian follicles begins when the female is in the uterus. You are born with nearly 1 to 2 million follicles that start to decline as you grow old. By the time you reach puberty, you have a total of 300,000 to 400,000 follicles. 

Each month during your menstrual cycle, a select group of follicles begin to grow and mature. While only one follicle is naturally selected most of the other follicles do not reach maturity and fade away on their own. 

During ovulation, one follicle develops to the right size and releases a mature egg.

Development stages of ovarian follicles 

The process of development and maturing of ovarian follicles is called folliculogenesis. There are different stages of ovarian follicles: 

  • Primordial follicles: Follicular development starts in the fetus.  During the first five months of development, nearly 1-2 million follicles form in the fetal ovary. At this stage, the follicles are known as primordial follicles. Your follicles remain at this stage till puberty. 
  • Primary follicle: Primordial follicles begin to develop and mature further when a woman reaches puberty. This stage provides the required support for oocyte growth. It is known as the primary follicle (further divided into early and late). 
  • Secondary follicle: Secondary follicles are largely different from primary follicles in their appearance. By this stage of development, the follicles compose cells that contribute to the production of estrogens. 
  • Antral follicle: Antral follicle, also known as the Graafian follicle, is the last stage of follicular development. At the Graafian follicle stage, the follicle has fully developed and ruptured from the ovum. This happens around the time of ovulation when one follicle becomes dominant and the others continue growing. 

What is the dominant ovarian follicle?

The “leading follicle,” or dominant ovarian follicle, is an essential component of the female reproductive system. A woman’s ovaries produce many follicles that start to grow during her menstrual cycle. One of the immature eggs in these follicles usually develops as the dominant follicle.

The follicle that grows larger and more quickly than the others is the dominant one. It is principally in charge of ovulation, which is the release of a developed egg from the ovary. The body selects the dominant follicle because of its superior hormonal signalling, which includes its increased secretion of the oestrogen form estradiol and its heightened sensitivity to luteinizing hormone (LH).

When the dominant follicle reaches a specific size, ovulation takes place, indicating the mature egg’s release into the fallopian tube, where sperm may fertilise it. The hormonal feedback mechanisms of the body play a complex role in controlling the growth and selection of the dominant follicle.

In order to predict when ovulation will occur and increase the likelihood of a successful conception, fertility specialists must have a thorough understanding of the dominant ovarian follicle. This is especially true for assisted reproductive techniques such as intrauterine insemination (IUI) and in vitro fertilisation (IVF).

Follicle size for Pregnancy

Follicles play an important role in determining your chances of getting pregnant as they ensure the ovulation process (the release of an egg from the ovaries). 

Nearly on the 14th day of your cycle, your follicles complete their development and begin to rupture. This process supports the release of a healthy, mature egg. The egg released from the follicle travels down the fallopian tube to be fertilised with sperm. 

The right egg size for pregnancy is dependent on the proper growth of follicles that results in a healthy pregnancy. 

Ovarian follicles are also responsible for the secretion of the hormone – estrogen which thickens the wall of the uterus and prepares it for pregnancy. Follicles also receive their growth spurt with the release of estrogen in the bloodstream. 

Must check about the ovulation calculator

Factors Affecting Ovary Size Change

There are a number of variables that can affect a woman’s ovarian size. Ovary size varies because of:

  • Menstrual Cycle: As ovaries grow and produce eggs, they typically enlarge during the follicular phase of the menstrual cycle, which occurs before to ovulation. The luteal phase follows, during which they shrink in size.
  • Pregnancy: The corpus luteum, which produces hormones to sustain pregnancy, and the growth of numerous follicles cause the ovaries to normally expand during pregnancy.
  • Polycystic Ovary Syndrome (PCOS): PCOS is characterised by the presence of several tiny cysts on the ovarian surface, which can lead to larger ovaries. Follicles that did not mature adequately are these cysts.
  • Ovarian Cysts: Whether harmful or functional, the formation of cysts can enlarge the ovaries.
  • Ovarian Tumours: Ovarian hypertrophy may result from benign or malignant tumours.
  • Hormonal Imbalances: Variations in hormone levels, such as those observed in hyperstimulation syndrome, might affect the size of the ovary.
  • Age: As women get closer to menopause, their ovaries tend to shrink in size and function less.
  • Medication: A number of drugs, particularly those used in IVF procedures, have the potential to alter ovarian size.

Changes in ovarian size are frequently evaluated by ultrasound imaging, and they may be a sign of a number of gynaecological disorders. Comprehending the variables that impact ovarian size is essential for precise diagnosis and suitable medical intervention.

Follicle and Fertility 

Your reproductive health is largely dependent on the size of your follicles and the quality of the eggs. 

If you have a good number of follicles, your potential of getting pregnant is higher as you have an abundance of immature eggs that can develop and burst leading to ovulation. It is thus recommended that women should try to conceive in their 20s. It is because, as mentioned earlier, the number of your follicles begins to decline as you age

The quality of your eggs is determined by your age and lifestyle choices.

What role does the follicle play in fertility treatment?

A wide range of fertility treatments for women includes ovarian stimulation. Your fertility doctor provides certain hormones and drugs to induce the development of follicles in your ovaries. These hormones stimulate the production of a higher number of healthy, mature eggs. Common hormone injections that are given include follicle-stimulating hormone (FSH), luteinizing hormone (LH) or both. 

Ovarian stimulation is an important step for various fertility treatments including IVF and IUI. While it is possible to achieve conception even with one mature follicle, it is preferable to have more follicles while undergoing fertility treatments. 

Your fertility doctor performs a routine pelvic ultrasound for regular monitoring of the number and size of follicles.

Antral follicle count test 

The antral follicle count (AFC) test is a screening test that helps visualise and evaluate a woman’s ovarian reserve. Ovarian reserve is the capacity of your ovaries to provide healthy eggs for fertilisation leading to a healthy pregnancy. 

AFC test is a transvaginal ultrasound. In this test, your fertility doctor inserts the probe of an ultrasound machine into the vagina to count the number of antral follicles. 

Follicles are clearly visible and can be counted at the antral stage through the AFC test. 

Besides evaluating the ovarian reserve, the antral follicle count test can help discover the following:

  • Provides an idea of how your age is affecting your fertility 
  • Identifies primary ovarian insufficiency 
  • Helps diagnose polycystic ovarian syndrome (PCOS)

The normal size of follicles for pregnancy

Besides follicle size for conceiving, the number of antral follicles are equally important. Your antral follicle count decreases as you grow old. Therefore, there is no single, exact number. 

If you are aged between 25 and 34 years, your follicle count should be nearly 15. While if you are above the age of 35, your follicle count may drop to 25 or lower. 

Follicles are required to develop and mature properly before rupturing and releasing a mature egg. The normal size of follicles for pregnancy is determined by an average diameter of 18-25 mm.

The Concluding Note 

Understanding the right follicle size for conceiving is important for couples to help them enhance their chances of pregnancy. The above article provides detailed information on follicle meaning and egg size for pregnancy.

If you need more information on egg quality and quantity or are looking for fertility treatment, you can consult Dr. Meenu Vashisht Ahuja at Birla Fertility & IVF.


  • How to increase ovarian follicle count?

You can increase ovarian follicle count through the following measures: eating a healthy diet, avoiding smoking, maintaining a healthy body weight, avoiding stress, improving your blood flow and taking fertility supplements.

  • What do ovarian follicles secrete?

Ovarian follicles are responsible for synthesising and secreting a range of hormones. Common hormones secreted by ovarian follicles are estrogens, progestins, and androgens.

  • What do ovarian follicles mean?

Ovarian follicles are tiny sacs in the ovaries filled with fluid. There are several thousand follicles in the ovaries. Each ovarian follicle contains one immature egg.

  • What is the minimum egg size to get pregnant?

According to ultrasound measurements taken during the follicular phase of the menstrual cycle, the minimum egg size needed for a healthy pregnancy is normally between 18 and 22 millimetres in diameter. The egg is developed and prepared for ovulation at this size. However, a woman’s overall reproductive health and the quality of her egg are also important factors in achieving a pregnancy. Furthermore, under certain conditions, assisted reproductive methods such as in vitro fertilisation (IVF) may utilise eggs that are smaller or less developed.

  • How many eggs will there be in a follicle?

An oocyte, or single egg, is typically present in a healthy follicle. Multiple follicles form in the ovaries of a woman during her menstrual cycle, but only one of these follicles matures into the dominant or “mature” follicle that releases an egg during ovulation. The process by which the remaining developing follicles usually deteriorate and are reabsorbed by the body is known as atresia. An important step in the menstrual cycle is the release of a single mature egg from the dominant follicle, which opens the door to the potential of fertilisation and pregnancy.

Written by:
Dr Meenu Vashisht Ahuja

Dr Meenu Vashisht Ahuja

Dr. Meenu Vashisht Ahuja is a highly experienced IVF specialist with more than 17 years of experience. She has worked with renowned IVF centers in Delhi and is a member of esteemed healthcare societies. With her expertise in high risk cases and recurrent failures, she provides comprehensive care in the field of infertility and reproductive medicine.
Rohini, New Delhi

Our Services

Fertility Treatments

Problems with fertility are both emotionally and medically challenging. At Birla Fertility & IVF, we focus on providing you with supportive, personalized care at every step of your journey towards becoming a parent.

Male Infertility

Male factor infertility accounts for almost 40%-50% of all infertility cases. Decreased sperm function can be the result of genetic, lifestyle, medical or environmental factors. Fortunately, most causes of male factor infertility can be easily diagnosed and treated.

We offer a comprehensive range of sperm retrieval procedures and treatments for couples with male factor infertility or sexual dysfunction.

Donor Services

We offer a comprehensive and supportive donor program to our patients who require donor sperm or donor eggs in their fertility treatments. We are partnered with reliable, government authorised banks to source quality assured donor samples which are carefully matched to you based on blood type and physical characteristics.

Fertility Preservation

Whether you have made an active decision to delay parenthood or are about to undergo medical treatments that may affect your reproductive health, we can help you explore options to preserve your fertility for the future.

Gynaecological Procedures

Some conditions that impact fertility in women such as blocked fallopian tubes, endometriosis, fibroids, and T-shaped uterus may be treatable with surgery. We offer a range of advanced laparoscopic and hysteroscopic procedures to diagnose and treat these issues.

Genetics & Diagnostics

Complete range of basic and advanced fertility investigations to diagnose causes of male and female infertility, making way for personalized treatment plans.

Our Blogs

By clicking Proceed, you agree to our Terms and Conditions and Privacy Policy

You can also reach us at

Do you have a question?