About the ovaries

What are the ovaries?

The ovaries form part of the female reproductive system. The ovaries are oval-shaped and around four centimetres long (roughly the size of an almond). The two ovaries sit either side of the uterus, supported by ligaments and the blood supply which comes from the side of the pelvis. The fallopian tubes run along the side of the ovaries into the uterus.

You may have ovaries if you are:

A woman who was assigned female at birth (recorded as female on her birth certificate).
A transgender man or non-binary person who was assigned female at birth.
An intersex person.
A man who has a difference in sex development (DSD).

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If you have previously had surgery on your reproductive system, such as a hysterectomy (removal of the womb), you may have had your ovaries removed (oophorectomy).

If you are not sure whether you have ovaries, it is best to speak to your GP.

What do the ovaries do?

The ovaries have two main functions:

1. They produce ova (eggs)

During a process called ovulation, which occurs midway through a normal menstrual cycle, the ovaries release an egg, which can then be fertilised by sperm in order to create an embryo. If this embryo then implants into the lining of uterus (womb), it may grow into a foetus.

Usually, only one egg is released each menstrual cycle. Sometimes however, the ovaries can release two eggs in one menstrual cycle (this can lead to the birth of non-identical twins if both eggs are fertilised).

Ovaries contain all the eggs that they will ever have at birth. More eggs will not be produced during a lifetime.

Ovaries release an egg (ovulate) once a month from puberty (the period during which people reach sexual maturity, usually during their teenage years) to the menopause (the time during which a person stops menstruating, i.e. having a period).

Some types of contraception can stop the ovulation process from happening, in order to prevent pregnancy. You will also not ovulate if you are pregnant.

2. They produce female sex hormones oestrogen and progesterone

These two hormones play an important role in the menstrual cycle.

Oestrogen production will be higher in the first half of the menstrual cycle, before the egg is released. When oestrogen levels are high, this causes a surge in a luteinizing hormone, which triggers the release of the egg from the ovary. Oestrogen also helps regulate cholesterol, keep your bones healthy and can affect skin and other tissues including the vagina. It helps with vaginal blood flow, lubrication and keeps vaginal tissue elastic.

Progesterone production will be higher in the second half of the menstrual cycle, after the egg has been released. Progesterone causes the lining of the uterus (womb) to thicken, ready for the egg to implant if it has been fertilised.

Oestrogen and progesterone levels fall after menopause. Hormone replacement therapy (HRT) uses both these hormones, unless you have had a hysterectomy, when oestrogen only HRT is usually used.

Ovarian cysts

Ovarian cysts are fluid-filled sacs which develop in the ovaries and are very common before the menopause. They are usually diagnosed by an ultrasound scan and sometimes also by blood tests. Symptoms can include those associated with ovarian cancer which we list here.

If an ovarian cyst is not causing any problems, the cyst may be monitored for changes depending on its size, but otherwise not treated. Sometimes hormonal contraceptives are prescribed to stop cysts recurring. If the cyst is large, causing symptoms, or if there is a suspicion the cyst is cancerous, then it may be removed by surgery. Up to one in ten people may need surgery for an ovarian cyst at some time in their life.

There are two main types of ovarian cysts: functional and pathological.

Functional ovarian cysts

These include cysts which are linked to the menstrual cycle such as follicular cysts, corpus luteum cysts and haemorrhagic cysts. They are not cancerous and will usually resolve on their own within two or three menstrual cycles.

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Pathological cysts

These are abnormal growths and can develop before or after the menopause. They include endometriomas, dermoid cysts (teratomas), and cystadenomas. Most of these cysts will not be cancerous. Pathological cysts can sometimes burst or grow very large; a small number will be cancerous. In these circumstances the cyst, possibly the whole ovary, will probably need to be surgically removed.

If a cyst bursts, it can cause sudden, severe pain. If the cyst causes your ovary to twist (torsion), you may have pain, nausea and vomiting. You may also experience faintness, dizziness, weakness and rapid breathing. If this occurs, you will need to go to your local emergency department.

After menopause

If you are post-menopausal, the recommendation is that a risk of malignancy index (RMI) should be completed by your doctor or specialist to guide the management of the ovarian cysts. This will help identify your risk of ovarian cancer and whether you should be treated by a general gynaecologist or by cancer services. It uses a blood test to check for ovarian cancer called CA125 and the appearances at ultrasound scan to provide a combined score or likelihood that any cyst is cancerous.

Polycystic ovary syndrome (PCOS)

Some people have a condition call Polycystic Ovary Syndrome (PCOS). This is very common; it is estimated that 1 in 10 women have PCOS.

(PCOS) is different to ovarian cysts. You are not at higher risk of ovarian cancer if you have PCOS, but your risk of endometrial cancer is slightly increased. Verity is the UK PCOS self-help organisation, you can view their website here.

Further information

NHS information on ovarian cysts

Royal College of Obstetricians and Gynaecologists patient information on ovarian cysts before the menopause

Royal College of Obstetricians and Gynaecologists guidance on ovarian cysts in post menopausal women

Royal College of Obstetricians and Gynaecologists guidance on ovarian masses in premenopausal women

Polycystic ovary syndrome (PCOS) is different to ovarian cysts. You are not at higher risk of ovarian cancer if you have PCOS, but your risk of endometrial cancer is slightly increased. Verity is the UK PCOS self-help organisation, you can view their website here.

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