Miscarriages are common, occurring in 15-20% of all pregnancies, usually in the first trimester (up to 13 weeks). One or even two miscarriages are not, by themselves, indicative of future infertility. Nonetheless, they may leave patients concerned and questioning their ability to have a live birth.

More than half of the time, families will go on to have healthy children, unassisted, after losing two pregnancies. However, you may want to look more closely at possible causes if you have not had a live birth and have had two or more miscarriages.

Types of miscarriage

There are many causes of miscarriage, but they are usually divided into two groups: early and late.

Recurrent early miscarriages (within the first trimester) are most commonly due to genetic or chromosomal problems of the embryo, with 50-80% of spontaneous losses having abnormal chromosomal numbers. Structural problems of the uterus can also play a role in early miscarriage.

Recurrent late miscarriage can be the result of uterine abnormalities, autoimmune problems, an incompetent cervix, or premature labor.

Finding a cause

A history of recurrent miscarriage calls for evaluation and management. At the Washington University Fertility and Reproductive Medicine Center, on both the mother or carrier and the father or sperm provider, as well as the fetal tissue, when applicable. These tests may include:

  • Anatomical testing/sonography (ultrasound test or HSG / X-ray)
  • Testing for auto-immune disorders (in cases of 3 or more losses)
  • Testing for insulin resistance, diabetes, and other endocrinopathies related to the thyroid and pituitary glands
  • Chromosome testing of products of conception after losses (we can test fetal DNA from formalin-fixed slides if you already had a miscarriage)
  • Blood clotting studies (*only indicated with personal or close family history of venous thrombo-embolism)
  • Chromosome testing of parents looking for balanced translocations

What causes recurrent pregnancy loss?

While oftentimes the reasons for miscarriage are not obvious, many patients go on to have a successful third pregnancy. Even after two miscarriages, there’s a 65% chance your third pregnancy will end in live birth.

However, if a cause is discovered, it may be easy to fix, and finding the cause at this point may prevent further losses and emotional stress. After two miscarriages, you have what is known as recurrent pregnancy loss and you may benefit from the diagnostic testing noted above to see if there is a reason for why you are miscarrying.

The intent of the above studies is to find a cause for the miscarriages, but in up to 50-75% of the cases, the testing comes back normal without any obvious answer.

Genetic (embryo or parents)

Random chromosomal abnormalities of the embryo are common and comprise 50-80% of all first-trimester losses. However, there are times when some chromosomal abnormalities are repeatedly passed on which can contribute to multiple pregnancy losses. If you have had two or more losses, you and your partner should consider a karyotype to check for a balanced translocation. The chance of finding a balanced translocation in either parent is 4%.

In some cases of recurrent pregnancy loss, in vitro fertilization with preimplantation genetic testing may be considered. The logic being that the loss is likely due to a chromosomally abnormal embryo, therefore selecting a chromosomally normal embryo will increase your chances of live birth.  This is highly individualized and should be considered in consultation with your physician.

Uterine anomalies

About 15% of all repeated miscarriages are caused by a uterine structural problem. Abnormalities of the uterus can be something that you’re born with (congenital), like a double uterus, a uterus that is divided by a wall (septate uterus), or other less common congenital problems.

There are also sometimes problems with fibroids or polyps, which are growths that can occur in any place within the uterus.

Intra-uterine scarring can also lead to miscarriages. The good news is that the majority of these problems can be dealt with prior to conception through surgery, thus increasing your chances of a healthy pregnancy. Proper evaluation is crucial to see if a problem like this exists.

Endocrine issues

Endocrine issues that warrant investigation include disease of the thyroid and pituitary glands, diabetes, or polycystic ovarian syndrome.

Luteal Phase defect (LPD) suggests that the ovaries of the uterus are suboptimal thus resulting in miscarriage. The first-line treatment for patients with an LFD is ovulation induction medications like clomiphene citrate.

In the past, progesterone therapy has been popular; however, there are few if any studies that demonstrate benefit from empiric progesterone therapy. An informed approach is always the best step in evaluating potential endocrine issues.

Autoimmune diseases: Antiphospholipid antibody syndrome

Immunological problems occur when the mother or carrier produces antibodies that indirectly cause clotting in blood vessels that lead to the developing fetus. The fetus is deprived of nutrients and dies in utero, causing a miscarriage.

A number of blood tests can be done to test for this problem if you have suffered 3 or more losses. There is treatment for this condition, with the aid of aspirin or heparin (an anticoagulant). If your doctor recommends daily aspirin therapy, you will probably use a low dose of aspirin (81 milligrams per day).

Heparin is an anticoagulant often prescribed to prevent blood clotting problems. You should discuss with your physician all of the short- and long-term risks associated with heparin during pregnancy. This therapy should only be utilized when it is truly warranted.

Blood clotting disorders are no longer felt to cause recurrent pregnancy loss, however, patients with a personal or family history of blood clots (in their extremities or lungs for example) should undergo testing for certain clotting disorders. This is a complex and confusing issue and a specialist will determine which testing is appropriate.

Environmental factors

Exposure to certain chemicals, drugs, x-rays, etc. may also increase the risk of miscarriage. Some of these factors are work-related, while others may be related to lifestyle. Excess use of alcohol or caffeine and smoking (first- and second-hand) by either partner may impact pregnancy outcomes. Obesity is associated with an increased risk of miscarriage.


Often, the reasons are unknown about multiple miscarriages. Even after two miscarriages, there’s a 65% chance that your third pregnancy will be fine. Seeking a physician who specializes in repeated miscarriages is important so that they can get to the root of the problem.

We are here to help. Please call us to schedule an appointment today.