Causes of Recurrent Miscarriage

woman talking to doctor

Miscarriage is one of the most devastating experiences that can happen to a woman. Having one miscarriage is, sadly, not that uncommon. Approximately two out of every ten pregnancies will result in miscarriage. After having one miscarriage, most women go on to have a healthy pregnancy. Still there are a few women that will continue to have two, three or even more miscarriages. Women are considered to have recurrent miscarriages when they have two or three miscarriages in a row. According to the American Society for Reproductive Medicine, only about one percent of women will have three consecutive miscarriages or more. Many doctors will not perform any tests until after a woman has had three consecutive miscarriages. Even with testing, doctors may not be able to determine the cause of recurrent miscarriage.

What Are the Causes of Recurrent Miscarriage?

Here Are Some of the Most Common Causes of Recurrent Miscarriage:

Genetic/Chromosomal Defects: Up to seventy percent of miscarriages are caused by chromosomal errors. Chromosomal abnormalities are more common in women who are over thirty-five. In most cases chromosomal defects are a random occurrence and are not likely to reoccur in subsequent pregnancies. Although chromosomal errors are the cause of the majority of miscarriages, they are not usually caused by an inherited trait from mother or father. Less than five percent of couples tested will have an inherited genetic cause of such chromosomal defects.

woman getting an ultrasou d

Age: After the age of thirty-five, the risk of miscarriage increases. After age forty, more than 33 percent of pregnancies will result in miscarriage. However, keep in mind the rate of miscarriage prior to age thirty-five is about ten to twenty percent.

Uterine Abnormalities: Uterus abnormalities account for ten to fifteen percent of repeated miscarriages. Some women are born with a double uterus or an abnormally shaped uterus. Other problems are scar tissue on the uterus. Uterus abnormalities may cause problems with proper implantation, create problems with blood supply to the uterus, or there may not be room for the baby to develop and grow.

Incompetent Cervix: Incompetent cervix may cause second trimester miscarriages or premature labor. Incompetent (or weakened) cervix may require a surgical procedure called cerclage. Cerclage is a surgical stitch around the cervix to help keep it from dilating prematurely.

Hormonal causes:

  • Luteal Phase Defect – Luteal phase defect occurs when there is not enough progesterone produced during the luteal phase of the menstrual cycle. Progesterone helps to prepare the lining of the uterus for implantation and creates a nutrient-rich environment for the developing baby. Some researchers believe that Luteal Phase Defect is responsible for up to forty percent of recurrent miscarriage; however, there are some questions as to the accuracy of these studies. Treatment for Luteal Phase Defect includes taking progesterone supplements or suppositories with future pregnancies. There is some controversy over prescribing progesterone for miscarriage treatment. There have not been enough controlled studies to confirm its effectiveness or to ensure its safe usage during pregnancy.

  • Polycystic Ovarian Syndrome – PCOS has been linked to miscarriage. Women with PCOS have higher levels of male hormones. This has been associated with infertility as well as miscarriage. Over a third of all women who have recurrent miscarriage also have PCOS. Treatment of PCOS often involves insulin-sensitizing medications. There is not enough evidence to show that this is an effective treatment for miscarriage; nor is there enough information on its safety during pregnancy.

  • Other Hormonal Conditions: Poorly controlled Type 1 Diabetes has been associated with miscarriage. Improving blood sugars before conception will improve the outcome during pregnancy.

lab tests

Autoimmune Disorders: Antibodies are designed to fight off infection in the human body. With certain autoimmune disorders, antibodies fight off the developing pregnancy tissues as if they are a foreign body or infection. Antiphospholipid syndrome (APS) is an autoimmune disorder diagnosed by blood tests that detect levels of anticardiolipin antibodies and lupus anticoagulant. Antibodies, such as anticardiolipin antibodies, can cause blood clots that clog up the blood supply to the placenta. Without the placenta supplying nutrients, the pregnancy will perish. Treatment for antiphospholipid syndrome includes low dose aspirin or heparin. The research is still out on these treatments effectiveness in preventing miscarriage.

Infection: Certain infections have been linked to miscarriage. Genital infections such as bacterial vaginosis may increase a woman’s risk of having a miscarriage. Testing for infections is not routinely done in women who have no symptoms of infection.

Male Factor: There is some evidence that defects in the male’s sperm may cause miscarriage. It is not known how often sperm defects are the cause of recurrent miscarriage.

Unknown Causes: Many couples do not find the cause of their recurrent miscarriages. Fifty percent or more do not find a cause even after testing. Furthermore, it is possible to have different causes for each miscarriage. With this consideration, it may not be possible to discover a pattern for a woman's miscarriages. The good news is that even if a woman has had multiple miscarriages, the odds of having a successful pregnancy are still in her favor. In sixty to seventy percent of couples with unexplained pregnancy loss, the couple will go on to have a successful pregnancy.

Sources: American Society for Reproductive Medicine American College of Obstetricians and Gynecologists March of Dimes