Endometriosis

Adenomyosis

When the tissue of the lining of the uterus grows into its muscle wall

In adenomyosis, glands and stroma of the endometrium, the lining of the uterus, grow into the myometrium, the muscle wall of the uterus. This tissue responds to the hormones of the cycle. It causes local inflammation, small bleeds within the muscle and thickening of the wall. The uterus often becomes larger and more tender.

Adenomyosis can be diffuse, when it affects a large part of the wall, or focal, when it forms a well-defined nodule, called an adenomyoma. It can also mainly affect the inner part of the myometrium, close to the lining, or the outer part, close to the surface of the uterus. The outer form is more often linked to endometriosis.

How are adenomyosis and endometriosis related?

In the past, adenomyosis was called “endometriosis of the uterus”. Today it is considered a separate disease, but it shares features with endometriosis. Both depend on estrogen, and in both the lining responds less to progesterone. The two diseases often occur together. How often depends strongly on the method of diagnosis and on the women studied. Among women with endometriosis and severe period pain, a large share also have adenomyosis. When both are present, pain is usually more severe and the chances of pregnancy are lower.

Why does it develop?

The exact cause is not known. The leading theory is that the basal layer of the lining enters the myometrium through small injuries at the border between the two tissues. These injuries can result from strong contractions of the uterus, from pregnancies or from procedures on the uterus, such as a cesarean section or a curettage. The uterus tries to heal these injuries, and this process increases local estrogen production and keeps the inflammation going.

Adenomyosis used to be seen as a disease of women over 40 who already had children. This picture arose because the diagnosis was made only after a hysterectomy. Today, with ultrasound and MRI, adenomyosis is diagnosed more and more often in young women, even in teenagers, and in women with infertility.

What are the symptoms?

The main symptoms are increased, prolonged bleeding during periods and severe period pain. Chronic pelvic pain, pain during sex and a feeling of heaviness in the abdomen are also common. Increased bleeding often leads to iron-deficiency anemia, with tiredness, weakness and shortness of breath on exertion. Some women have no symptoms at all, and adenomyosis is found by chance on ultrasound.

Adenomyosis also affects fertility and the course of pregnancy. It is often discovered in women with repeated implantation failure or miscarriages.

How is the diagnosis made?

The diagnosis is based on transvaginal ultrasound by an experienced doctor. The international MUSA group has set common criteria for describing adenomyosis. The 2022 revision distinguishes direct signs, which show endometrial tissue within the muscle, such as small cysts and bright islands, from indirect signs, such as asymmetrical thickening of the wall and acoustic shadows. MRI helps when the ultrasound is not clear or before a procedure. Blood tests are not used for the diagnosis. The final diagnosis is made by examining the tissue after surgery. Surgery is not needed, however, to suspect adenomyosis or to start treatment.

The diagnosis does not rely on the image alone. The assessment combines the findings with the symptoms, the woman's age and her plans for pregnancy. Mild adenomyosis without symptoms does not always need treatment.

How does adenomyosis affect fertility?

Adenomyosis lowers the chances of pregnancy. In a 2014 meta-analysis, after IVF a clinical pregnancy was achieved in 40.5% of women with adenomyosis, compared with 49.8% of women without it. In the pooled statistical analysis of the studies, the chance of a clinical pregnancy was 28% lower. Miscarriages were more than twice as common, at 31.9% compared with 14.1%. A more recent meta-analysis from 2021 confirmed the lower chance of pregnancy and the doubled risk of miscarriage.

The cause seems to lie mainly in the uterus, in a disturbed function of the lining, in inflammation and in abnormal contractions of the myometrium, which make implantation harder. Treatment before trying to conceive, for example with a GnRH agonist before a frozen embryo transfer, is often used. The data on its benefit, however, are not yet clear, and the decision is made individually.

How does adenomyosis affect pregnancy?

Adenomyosis also affects the pregnancy itself, however the pregnancy was conceived. The 2021 meta-analysis showed a higher risk of pre-eclampsia, preterm birth, cesarean section, abnormal position of the baby, a baby that is small for gestational age and bleeding after birth. For this reason, the pregnancy of a woman with adenomyosis needs closer monitoring.

How is it treated with medication?

Anti-inflammatory painkillers and tranexamic acid reduce pain and bleeding. They help mainly with mild symptoms or as an addition to hormonal treatment.

The levonorgestrel hormonal IUD is the best-studied hormonal treatment for adenomyosis. It reduces pain, bleeding and the size of the uterus, and it can stay in place for years. A 2025 meta-analysis showed that combining the IUD with a GnRH agonist for a few months works better than the IUD alone. Dienogest and combined contraceptives are also options. GnRH agonists shrink the uterus and stop the period, but their effect is temporary. They are usually used for a few months, before a procedure or before an embryo transfer.

Adenomyosis often responds less well than endometriosis to the usual treatments. The quality of the studies is still limited, and many treatments are not specifically approved for adenomyosis. For this reason, treatment needs specialized expertise and regular review.

What procedures are available?

When medication is not enough, there are procedures that preserve the uterus. In focal adenomyosis, the surgeon can remove the adenomyoma. This operation, however, leaves a scar in the wall of the uterus, which increases the risk of uterine rupture in a future pregnancy. Uterine artery embolization and high-intensity focused ultrasound (HIFU) reduce symptoms in selected women. Data on future pregnancy after these methods, however, are limited.

Hysterectomy is the only definitive treatment. It is considered when a woman does not want another pregnancy and other treatments have not helped. The ovaries are usually kept, to avoid an early menopause.

What happens after the menopause?

Adenomyosis depends on estrogen. For this reason, symptoms usually settle after the menopause and the uterus becomes smaller. When a woman with adenomyosis needs hormone replacement therapy, the doctor chooses a combined treatment with estrogen and progesterone, as in endometriosis.

The practice's approach

Sources: Chapron C et al., Diagnosing adenomyosis: an integrated clinical and imaging approach, Human Reproduction Update 2020. Harmsen MJ et al., Consensus on revised definitions of Morphological Uterus Sonographic Assessment (MUSA) features of adenomyosis: results of modified Delphi procedure, Ultrasound in Obstetrics & Gynecology 2022. Vercellini P et al., Uterine adenomyosis and in vitro fertilization outcome: a systematic review and meta-analysis, Human Reproduction 2014. Nirgianakis K et al., Fertility, pregnancy and neonatal outcomes of patients with adenomyosis: a systematic review and meta-analysis, Reproductive BioMedicine Online 2021. Zhang B et al., The role of different LNG-IUS therapies in the management of adenomyosis: a systematic review and meta-analysis, Reproductive Biology and Endocrinology 2025. Becker CM et al., ESHRE guideline: endometriosis, Human Reproduction Open 2022. Leyendecker G et al., Adenomyosis and endometriosis. Re-visiting their association and further insights into the mechanisms of auto-traumatisation. An MRI study, Archives of Gynecology and Obstetrics 2015.