A pregnancy that ends before 20 weeks is called a miscarriage. Most miscarriages happen before the end of the first trimester (the first 12 weeks) of pregnancy. “Miscarriages are more common than most couples would suspect,” says William Hurd, MD, director of the MacDonald Fertility and IVF Program at UH MacDonald Women’s Hospital. “It is estimated that every confirmed pregnancy has a 10 to 15 percent chance of ending in miscarriage.”

For women who have had one miscarriage, their chances of carrying the next pregnancy to full term remain about the same as if they had never had one. The chance of miscarrying again after two miscarriages increases with each loss. The risk for recurrent miscarriage also increases with age. Women 40 years or older with previous recurring miscarriages have a much higher risk compared with younger women.

The American College of Obstetricians and Gynecologists defines recurrent miscarriage as two or more consecutive pregnancy losses in the first trimester or early second trimester. In the past, a woman who experienced more than one miscarriage might never know why they happened. Today, more and more women are finding out what has caused their recurrent miscarriages.

There are many different reasons for miscarriage, including fetal chromosomal defects, hormonal problems, abnormalities of the uterus and medical problems that increase the risk for blood clots. According to Dr. Hurd, a thorough evaluation for these problems can usually be completed within a month. Unfortunately, even with this approach, a cause will not be identified in more than 50 percent of women with recurrent miscarriages. Dr. Hurd is currently conducting studies to identify previously undetected causes in these patients. When specific causes are found, they can often be successfully treated, says Dr. Hurd. All patients should try to lead a healthy lifestyle to minimize the risk for miscarriage, including smoking cessation, weight control and reduction of both alcohol and caffeine. For women with no identifiable cause, the UH program offers several standard and experimental treatment options. In addition, it appears that informative and sympathetic counseling might play an important role in decreasing miscarriages, and UH MacDonald Women’s Hospital’s Division of Behavioral Health specializes in the psychological aspect of women’s reproductive health issues.

Causes of Miscarriage

William Hurd, MD, director of the MacDonald Fertility and IVF Program at UH MacDonald Women’s Hospital, recommends that patients ask their doctors about these possible causes of miscarriage.

Genetic Factors
Problems with fetal chromosomes are among the most common causes of miscarriage with first trimester pregnancy losses. They can be either inherited from the parents or occur for the first time in the fetus.

Anatomical Factors
Uterine abnormalities are associated with both first and second trimester pregnancy losses. Abnormalities present at birth include a double uterus and uterine septum. Acquired abnormalities include uterine polyps, fibroids and scar tissue inside the uterine cavity.

Cervical Incompetence
Incompetent cervix complicates about 1 percent of pregnancies. Women with an incompetent cervix often deliver between 16 and 18 weeks with minimal pain. This condition can be successfully treated with a stitch to help hold the cervix closed.

Smoking
Cigarette smoking increases the risk for recurrent miscarriage. Women trying to achieve pregnancy should not smoke.

Immunology
Immune problems are associated with 3 to 15 percent of recurrent miscarriages. The most common immune problems are systemic lupus erythematosus and antiphospholipid antibody syndrome.