What Are the Causes of Recurrent Miscarriage?

Recurrent miscarriage causes are not yet well understood by the medical community. There is much disagreement on which factors lead to miscarriages and on which possible causes ought to be treated. A few practices are relatively standard, while others are more controversial.

Possible Causes of Recurrent Miscarriage

Possible recurrent miscarriage causes generally fall into the following categories:

• Anatomical
• Blood clotting/immunological
• Hormonal
• Genetic
• Unknown

Anatomical Causes

Sometimes, something is physically different about a woman’s uterus in a way that reduces her chances of a successful pregnancy. This might mean her uterine shape is abnormal or her cervix is weakened in a way that reduces her odds of a successful pregnancy. Anatomical factors that may cause recurrent miscarriages include:

• Uterine septum (or other congenital problems)
• Cervical insufficiency
• Fibroids (controversial)
• Uterine scarring

Blood Clotting Tendencies

The exact mechanisms by which blood clotting disorders cause miscarriages are not yet well understood, but the primary condition in this category that doctors test for is called antiphospholipid syndrome. Hereditary thrombophilias, such as Factor V Leiden, have been implicated in late pregnancy losses.

You may find mention of other immune system-based miscarriage causes around the Internet, such as elevated Natural Killer cells or HLA incompatibility, but these factors are not widely accepted as miscarriage causes by the mainstream medical community.

Hormonal/Endocrine Causes

The idea that hormonal problems cause recurrent miscarriages is controversial. Progesterone deficiency, particularly, is hotly debated, and asking different doctors about the issue may result in different answers. Low progesterone should be considered inconclusive as a recurrent miscarriage cause. These conditions have been tied to recurrent miscarriages also, but they require more research.

• Elevated prolactin
• Insulin resistance
• Thyroid disorders

Genetic Causes

Sometimes, recurrent miscarriages do have a chromosomal cause. Women (and men) older than 35 have a greater tendency to produce eggs or sperm with chromosomal abnormalities.

In other cases, one or both partners may have a balanced translocation or other silent chromosomal abnormality that gives the couple statistically increased odds of miscarriage in each pregnancy.

Unknown Causes

Medical practitioners can find a cause for a couple’s recurrent miscarriages only about half the time. The other half of the time, the cause is unknown. If you end up falling into this category, take heart. Studies have found that couples with recurrent miscarriage due to unknown causes have a 70 percent chance of eventually having a normal pregnancy.

General Information

It might seem unfair that you have to miscarry twice, or even three times, in order to get any kind of testing. But because the majority of women who have one miscarriage go on to have a successful subsequent pregnancy, doctors do not usually order tests after the first pregnancy loss. The testing can be expensive, and insurance companies do not always cover the cost of the tests.

In pursuing a testing workup, find a doctor whose judgment you trust. If your doctor tells you that you have to miscarry three times in order to get testing, remember that many doctors will run tests after two losses and consider finding a new doctor, possibly a specialist.

You may feel some trepidation over the idea of trying again after a loss. Try to take heart, however, in that a thorough testing workup should be able to ease your concerns. If test results reveal a problem, then you know about that problem and can treat it, thus improving the odds for your next pregnancy.

If tests don’t reveal a problem, at least you will be able to try again knowing that you don’t have a treatable medical condition that needs addressing.