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:

• Genetic causes
• Medical conditions such as lupus or antiphospholipid syndrome, and diseases such diabetes or thyroid disease
• Physical problems with the uterus and cervix

Your health care 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.

In the weeks following fertilization, the blood vessels in the lining of the uterus undergo a number of changes to support a newly implanted embryo. Damage to the uterus caused by fibroids, scarring, or infection may impair this vital development.

Variations in the shape of the uterus can also affect the development of the lining or impair implantation of the embryo. One kind of variation is called a "uterine septum." 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.

Underdevelopment of the lining of the uterus is another problem which may prevent the implantation or full development of the embryo. Accurate testing for this is not yet available, however, your provider may suggest supplementing with progesterone in the first trimester of pregnancy. Progesterone is a key hormone already produced by your body. Supplementing in the early stages of pregnancy may improve the development of the lining of the uterus.

Supporting the entrance to the uterus is the cervix, a ring of muscle that plays a critical role in keeping the pregnancy in place. As pregnancy progresses into the second trimester, the expanding uterus places more and more pressure on the cervix. If the cervix is weakened, it may shorten and open too soon, leading to miscarriage or to the birth of a very premature infant. This condition, called cervical insufficiency, can only be diagnosed by monitoring the cervix during pregnancy; however, because it tends to happen more than once, your provider may be able to predict that you have a weakened cervix if you had similar problems with a previous pregnancy.

If you have this condition, your provider may suggest starting progesterone in the second trimester to support the cervix. They may also recommend a treatment called cervical cerclage. Cervical cerclage involves sewing a stitch using surgical thread in and around your cervix to keep it closed longer. This procedure is done in the operating room.

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.