Can High Prolactin Levels Cause Repeated Pregnancy Loss or PMOS?

When women have difficulty becoming pregnant or experience repeated pregnancy loss, doctors may look at several possible causes, including the uterus, egg quality and ovarian health. Hormones can also play an important role. One hormone that may need attention in some cases is prolactin.

Prolactin is produced by the pituitary gland. Its main role is to support breast milk production during pregnancy and breastfeeding. However, prolactin levels that remain unusually high outside these periods can affect the reproductive system. This condition is known as hyperprolactinaemia.

High prolactin levels may cause irregular or absent periods and can make it difficult to become pregnant. Some women may also experience unexpected milk-like discharge from the breasts. However, high prolactin does not always cause noticeable symptoms.

Prolactin is connected to the wider hormonal system that controls reproduction. When prolactin levels are too high, they can interfere with the hormones responsible for ovulation. This may result in irregular or absent ovulation, reducing the chances of conception.

There is also some evidence linking high prolactin with recurrent pregnancy loss in certain women. A 2025 guideline published in the Journal of Obstetrics and Gynaecology Canada noted that elevated prolactin may be associated with problems affecting the early stages of pregnancy. The guideline suggests considering prolactin testing in women with recurrent pregnancy loss when they also have irregular menstrual cycles or unexpected breast discharge.

However, high prolactin is only one possible factor behind infertility or repeated pregnancy loss. Other causes can include chromosomal problems in embryos, abnormalities of the uterus, thyroid disorders and antiphospholipid syndrome. Doctors may therefore need to carry out a broader evaluation rather than focusing on prolactin alone.

Thyroid health is particularly important because hypothyroidism can also increase prolactin levels. In women with PMOS, previously known as PCOS, mildly elevated prolactin may sometimes occur along with other hormonal changes. Studies have reported that elevated prolactin is found in some women with PMOS, although the reported percentage can vary between different studies and populations.

Several conditions and factors can cause high prolactin. These include pituitary tumours, hypothyroidism, certain medicines, stress and intense physical exercise. Because temporary factors can affect prolactin levels, testing is generally done under appropriate and standard conditions. If an abnormal result is found, doctors may recommend repeat testing or additional investigations.

When hyperprolactinaemia is confirmed, treatment depends on the underlying cause. Medicines known as dopamine agonists, including cabergoline and bromocriptine, are commonly used in appropriate cases to lower prolactin levels. Treating the underlying problem can help restore normal reproductive function and may improve the chances of pregnancy.

For women experiencing infertility or recurrent pregnancy loss, prolactin testing may be useful when symptoms or medical history suggest a possible hormonal problem. However, test results should always be interpreted by a healthcare professional alongside thyroid function, ovulation, ovarian health and other reproductive factors.

High prolactin can affect fertility, but it is not the only possible explanation for difficulty conceiving or pregnancy loss. A complete medical evaluation is important to identify the underlying cause and choose appropriate treatment.