If you are pregnant and you lose the baby before 20 weeks, it is called a miscarriage. Most miscarriages happen before 12 weeks. This is the end of the first trimester. Many happen before you even know you are pregnant. In the past, a woman who miscarried many times might never know why it happened. Today, more and more women are finding out the causes of their recurrent (repeated) pregnancy loss.

Repeated pregnancy loss is when you have two or more miscarriages in a row. This usually happens in the first trimester or early second trimester. Miscarriages are common. You have a 15% to 20% chance of your pregnancy ending in miscarriage.

If you have lost a single pregnancy, don't worry. Your chances of carrying the next pregnancy to full term stay about the same as if you had never had a pregnancy loss. The chance of having a pregnancy loss again after two pregnancy losses grows with each loss. The risk for repeated pregnancy loss goes up with age. If you are age 40 or older with previous repeated pregnancy loss, you have a much higher risk compared with younger women.

There are many different reasons for pregnancy loss. Ask your doctor about these possible reasons:

• Genetic problems. Problems with the genes or chromosomes of the baby are the most common reason for a first pregnancy loss. This often happens all of a sudden, by chance, in the embryo. This is usually less often the cause for women with repeated pregnancy loss.
• Problems with the uterus. Problems with the uterus can cause both first and second trimester pregnancy losses. Problems you are born with (congenital) include double uterus or uterine septum. Other problems are uterine polyps, fibroids, and scar tissue inside the uterine cavity.
• Cervical insufficiency. This is sometimes called incompetent cervix. If you have cervical insufficiency, you will lose the pregnancy around 20 weeks. This problem can be treated with a stitch to help hold the cervix closed or progesterone supplementation.
• Being exposed to certain chemicals. If you or your partner is exposed to certain chemicals, it could cause pregnancy loss. Some chemicals that may be linked to it include: anesthetic gases (nitrous oxide), pesticides, formaldehyde, benzene, ethylene oxide, arsenic, lead, mercury, and cadmium. You and your partner should talk with your doctor about any chemicals in the workplace.
• Endocrine problems. Some endocrine problems have been linked to pregnancy loss. These include diabetes (that is not controlled), severe thyroid problems, or luteal phase defect.
• Smoking, drinking, and drug use. Smoking, drinking, and illegal drug use can cause repeated pregnancy loss. You should not smoke. You should also stay away from alcohol and drugs during pregnancy.
• Immune problem. An immune problem called antiphospholipid syndrome causes repeated pregnancy loss in some women. This problem can be treated with low-dose aspirin and heparin.

Testing and treatment may be done after the second miscarriage in a row. A lot of the testing and treatment are controversial. Also, the reasons that some treatments work are not well understood.

It is likely that you will go on to have a healthy baby even if you've suffered repeated pregnancy loss. Informative and caring counseling seem to play a big role.

These things can raise your chance of having a healthy and successful pregnancy:

• Having a healthy lifestyle
• Taking a folic acid supplement
• Quitting smoking
• Controlling your weight
• Not drinking alcohol
• Reducing the amount of caffeine in your diet