Miscarriage and Stillbirth Causes

There Are a Few Known Causes for Pregnancy Loss, but Many Questions Still Remain

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After a pregnancy loss, most couples want answers. Many people wonder if the loss happened because of something they did, or if the miscarriage or stillbirth could have been prevented somehow.

Usually, the answer to that question is no. Miscarriage and stillbirth are rarely anyone's fault, and sometimes pregnancy loss is even a predetermined outcome at the time of conception.

Even though we know pregnancy loss usually does not happen because of anything the mother (or father) did, doctors cannot always explain why they do happen.

What Causes a Miscarriage?

Sporadic, one-time pregnancy losses are often caused by random chromosomal abnormalities in the developing baby. The medical community widely recognizes this explanation. In many cases, doctors assume this as the default explanation for first time miscarriages—with good reason, given that most couples go on to have a normal pregnancy after one miscarriage.

In most cases, a pregnancy lost to miscarriage has a problem in the chromosomes, such as extra chromosomes or missing chromosomes that cause the pregnancy to stop developing and eventually be miscarried. Because chromosomal flaws are usually random, one-time events, most doctors do not initiate testing for miscarriage causes after the first miscarriage.

Anyone can have a miscarriage due to chromosomal flaws, regardless of age, but the highest risk for this particular problem is with mothers aged 35 years or older.

While chromosomal abnormalities are the most common cause of miscarriage, there are other things that can result in miscarriage. These include:

The earlier a miscarriage happens in a pregnancy, the more likely it is due to a chromosomal problem. Miscarriages during the second trimester are less common than during the first trimester.

What Causes Recurrent Miscarriages?

Two miscarriages qualify as recurrent miscarriages, and after three repeat miscarriages, testing is recommended, according to the American College of Obstetricians and Gynecologists. Approximately one percent of women experience repeat miscarriages.

About 25 to 50 percent the time, doctors can find a cause for recurrent miscarriages and the woman can be treated in her next pregnancy. But in about 50 to 75 percent of cases, tests do not reveal a cause. But even with recurrent miscarriages, a woman can get pregnant again and still have greater statistical odds of a normal pregnancy than another loss.

Widely recognized causes of recurrent miscarriages include the following:

What Causes Stillbirth?

Stillbirths (pregnancy loss after the 20th week) usually have different causes from earlier miscarriages, although chromosomal errors in the baby can cause stillbirths.

Other common causes of stillbirth are cervical insufficiencies, placental problems, infection, blood clotting disorders in the mother, and uterine abnormalities.

Support After a Miscarriage or Stillbirth

Your doctor should be able to give you information on whether you need testing for pregnancy loss risk factors and causes. Regardless of the cause, if you have had a miscarriage or a stillbirth, be sure to seek out emotional support from friends and relatives or look for support groups if you don't have an adequate support structure. You should not have to go through this alone. 

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By Krissi Danielsson
Krissi Danielsson, MD is a doctor of family medicine and an advocate for those who have experienced miscarriage.