Updated by the Progyny Clinical Team — September 2025.
Polycystic ovary syndrome (PCOS) is a common hormonal condition that affects about 10% of people with ovaries during their reproductive years.
The exact cause is not known, but PCOS happens when hormones are out of balance. These imbalances affect how the ovaries grow and release eggs, making it harder to become pregnant. PCOS is one of the most common and treatable causes of infertility.
What is PCOS?
PCOS is the most common hormonal disorder among people with ovaries of reproductive age, affecting 5% to 15% worldwide. It affects all races and ethnicities.
PCOS is often defined by three main signs:
- Irregular or missed menstrual cycles
- High levels of testosterone or other androgens
- Ovaries with many small fluid-filled sacs (follicles)
Many people with PCOS are also at risk for insulin resistance. This means the body does not use insulin well, which can raise the risk of type 2 diabetes and other health problems.
How PCOS affects ovulation
In a typical menstrual cycle, the brain sends signals to the ovaries to grow and release one egg. With PCOS, the ovaries do not respond as they should. Several small follicles may form, but no single follicle grows enough to release an egg.
On an ultrasound, these small follicles may look like a “string of pearls.” The name can be confusing. PCOS does not mean the ovaries have large cysts. Instead, the ovaries have many small follicles that hold eggs. Without regular ovulation, periods may be irregular or absent.
Some people with a high number of eggs (ovarian reserve) may have ovaries that look similar to PCOS on ultrasound. That’s why diagnosis should include symptoms, not ultrasound findings alone.
What causes PCOS?
The cause of PCOS is not fully understood. It is called a syndrome because it involves a group of symptoms, not one single condition.
Genetic links
It often runs in families, which suggests a genetic role. But there is no single PCOS gene. Researchers believe genetics, as well as prenatal and environmental factors, may all play a part.
Other factors
The ovaries often make higher levels of androgens, which can affect egg development and ovulation. When the body does not use insulin well, insulin levels rise. This can trigger the ovaries to make more androgens. Some research suggests that long-term, low-grade inflammation may cause the ovaries to make more androgens.
Can you get pregnant with PCOS?
Yes. Infertility with PCOS is often caused by irregular ovulation, but this can be treated with medications that help the ovaries release eggs. For some people, lifestyle changes — such as weight loss — may restore regular cycles and improve the chance of pregnancy. Not everyone with PCOS will have trouble getting pregnant.
Beyond fertility
PCOS affects more than fertility. It is linked to health concerns involving metabolism, the heart, skin, and mental health. Because of this, many people work with a team of healthcare providers to support their overall health.
If you have questions or concerns, Progyny is here for you. Please contact your Progyny Care Advocate for support.
Disclaimer: The information provided by Progyny is for educational purposes only and is not medical advice. Always consult a qualified healthcare provider for medical guidance.