Across Canada there is no single definition of recurrent pregnancy loss, but at BC Women's we mean - two or more losses, one after the other, before 20 weeks gestation.

The causes of recurrent pregnancy loss are not always known, however they usually fall into three main categories: 

Your healthcare provider can help you determine whether you should be tested for any of these conditions.

The most common causes of miscarriage are random genetic errors that occur before or during the development of the embryo. The most common of these is called aneuploidy. 

Aneuploidy happens when an embryo has too many or too few chromosomes.  For more information about aneuploidy, see the Miscarriage page.

Some causes of miscarriage can be treated or managed. These treatable causes include medical conditions or diseases, and physical problems with the uterus or cervix.

Medical Conditions and Diseases 

If you have a medical condition such as high blood pressure, diabetes, a thyroid or an autoimmune disease, it may be difficult for your pregnancy to develop fully. Although the reasons are not entirely clear, these conditions seem to interfere with the early development of blood vessels in the placenta which are needed to supply blood to the growing pregnancy. Working with your provider to manage your condition is important, not only for your own health, but to reduce your risk of miscarriage and ensure a healthy start to any future pregnancy. 

Antiphospholipid syndrome is one example of an autoimmune disease that may affect pregnancy. It is a rare medical condition which may cause your immune system to produce antibodies that work against the new pregnancy. People with antiphospholipid syndrome are more likely to experience recurrent pregnancy loss, as well as complications in pregnancy such as pre-eclampsia, an underweight baby, or even stillbirth. Antiphospholipid syndrome can be identified through blood testing. If you have this condition, use of low dose Aspirin or other medications such as Heparin can increase your chances of carrying a pregnancy to full term. 

Genetic testing

Aneuploidy, the most common genetic cause of miscarriage, occurs randomly and cannot be prevented or treated. But there are other, less common genetic variations that occur at the time of fertilization. In some cases these variations may be inherited from one or both parents. Genetic testing may be used to find out if you or your partner have this type of genetic variation. If a genetic variation is found, you will be referred to a genetic counsellor to discuss your results and how this may affect your future pregnancies.

Physical tests for the cervix and uterus

The most common tests used to identify variations in the shape of the uterus or the presence of a uterine septum are hysteroscopy and hysterosalpingogram (also called an HSG).

A hysteroscopy involves filling your uterus with a salt water solution using a small tube called a hysteroscope which is inserted through your vagina into the uterus. The hysteroscope contains a camera which allows your provider to look for any anatomical problems with the uterus.

An HSG test is an X-ray of your uterus and fallopian tubes. During this test a special fluid is placed in the uterus so that the walls of the uterus and fallopian tubes can be clearly seen on X-ray. As the fluid moves, your provider looks for any blockages in the fallopian tubes or unusual divisions in the uterus.

In addition to these tests, you may be asked to have an endometrial biopsy. A biopsy involves removing a small piece of tissue from the lining of your uterus and testing it to determine if there is an infection. If one is found, antibiotics may be used to treat the infection.

After testing you will review the results with your gynecologist and decide on the next steps together.

It is important to acknowledge that testing may not provide you with all the answers. More and more studies are being done but we still have much to learn about why recurrent pregnancy loss happens. Testing may help to rule out the most common contributors to recurrent pregnancy loss and allow you to work with a provider to create a personalized care plan

Research has shown that between 50 and 75% of people will go on to have a successful pregnancy after multiple losses - even when no treatable cause can be found. It is important to work with a knowledgeable and supportive gynecologist to create a care plan designed to give you the best chance of a successful pregnancy.

Below are some terms you may hear providers use when talking about recurrent pregnancy loss. For other terms related to miscarriage, see the glossary near the bottom of the miscarriage page.

Adenomyosis - a condition in which the endometrial tissue that normally lines the uterus,  grows into the muscle of the uterus.

Antiphospholipid syndrome - an autoimmune disease that may affect pregnancy. It is a rare medical condition which may cause your immune system to produce antibodies that work against the new pregnancy. 

Arcuate uterus - a minor variation in the shape of the uterus. A typical uterus is pear-shaped, but an arcuate uterus has a small dent at the top. This dent does not cause health concerns nor does it require treatment (unlike the condition called "uterine septum"; see below).

Balanced translocation - a type of genetic variation in which one piece of a chromosome attaches to another piece from a different chromosome pair. The overall number of chromosomes is still correct, so it is considered "balanced" but the chromosome sections are joined in the wrong place. An estimated 1 in 560 people have a balanced translocation. It can be an inherited trait or can occur in a embryo even when neither parent is affected by the condition. People with this condition are at a greater risk of recurrent miscarriage.

Cervical insufficiency - a condition in which the cervix is weakened and may open too soon in the pregnancy leading to miscarriage or a very premature infant.

Cervical cerclage - a surgical treatment to address cervical insufficiency. This involves sewing a stitch using surgical thread in and around the cervix to keep it closed longer.

Chronic histiocytic intervillositis (CHI)  - a rare but often recurrent condition in which there are lesions on the placenta.  Pregnancies with CHI are at high risk of fetal growth restriction, miscarriage or stillbirth.

Cytogenetic testing -  involves testing samples of tissue, blood, or bone marrow in a laboratory to look for changes in chromosomes, including broken, missing, rearranged, or extra chromosomes.

Fibroids -  are tumors that grow in the wall of the uterus. They are usually benign (non-cancerous) and can grow as a single tumor, or there can be many of them in the uterus. 

Hysterosalpingogram (HSG)  - an X-ray of your uterus and fallopian tubes. During this test a special fluid is placed in the uterus so that the walls of the uterus and fallopian tubes can be clearly seen on X-ray. As the fluid moves, your provider looks for any blockages in the fallopian tubes or unusual divisions in the uterus.

Hysteroscopy  - a test used to look for physical problems in the uterus. A small tube called a hysteroscope is inserted through your vagina into the uterus. The uterus is filled with a fluid to cause it to expand. The hysteroscope, which contains a camera which allows your provider to look for any anatomical problems with the uterus.

Uterine septum - is a condition you are born with. It occurs when an extra piece of tissue known as a septum hangs from the top of the uterus. It may be small, or it may be large enough to divide the uterus into two halves. A significant uterine septum can cause problems with blood circulation in the lining and may prevent the embryo from implanting or developing fully. Surgery can help to correct this.