Miscarriage is when a baby dies in the womb before 20 weeks of pregnancy.
Usually, miscarriage is a one-time thing. Most women who miscarry don’t have the same problem in another pregnancy. But about 1 percent of couples have repeat miscarriages. This means the woman has two, three or more miscarriages in a row.
There may be some specific problem that causes repeat miscarriages. But these causes are known in only half of all cases. Even without treatment, about 60 to 70 percent of women with repeat miscarriages go on to have a successful pregnancy.
What causes repeat miscarriages?
Known causes of repeat miscarriages include:
Problems with the uterus or cervix. The uterus (womb) is where your baby grows inside you. The cervix is the opening to the uterus that sits at the top of the vagina. Problems with the uterus and cervix cause 10 to 15 percent of repeat miscarriages. Examples include:
- A uterus that isn’t shaped correctly or is divided in two. Sometimes these can be corrected with surgery.
- Fibroids (growths) in the uterus or scars from surgery on the uterus. Fibroids and scars can limit space for the baby or interfere with the baby’s blood supply.
- Cervical insufficiency (also called incompetent cervix). This is when the cervix is weak and opens too early. This can lead to miscarriage, usually in the second trimester. To help prevent miscarriage, your provider may recommend cerclage. This is a stitch your provider puts in your cervix to help keep it closed.
Chromosome problems. Chromosomes are tiny, thread-like structures in cells that carry our genes. Each person has 23 pairs of chromosomes (46 in all). One chromosome in each pair comes from the mother, and the other comes from the father. Most chromosome problems happen when an egg or sperm has too many or too few chromosomes. Chromosome problems usually happen just once. But in about 2 to 4 percent of couples with repeat miscarriages, one parent has a chromosome problem that doesn't affect his own health but can cause problems in the baby. Both parents should have a test called a karyotype to check for chromosome problems.
Antiphospholipid syndrome. This is a condition of the immune system that increases the risk of blood clots in the placenta. Your immune system is what protects your body from infection. Antiphospholipid syndrome causes 5 to 10 percent of repeat miscarriages. Your provider can test you for this condition with a blood test. Treatment is with low doses of aspirin and a medicine that helps thin the blood.
Hormone problems. Hormones are chemicals made by the body. If you have too much or too little of certain hormones, your chances of miscarriage may increase.
- Luteal phase defect. This is when you have low levels of progesterone over several menstrual cycles. Progesterone is a hormone that helps regulate your monthly periods and gets your body ready for pregnancy. Your provider may recommend treatment with various forms of progesterone.
- Polycystic ovary syndrome (also called PCOS). This condition happens when you have hormone problems along with cysts on the ovaries. A cyst is a closed pocket of that contains air, fluid or semi-solid substances. Your provider may recommend treatment with progesterone or other medicine.
Blood-clotting conditions called thrombophilias. This group of conditions is inherited, which means it’s passed down from parents to children. It increases the risk of blood clots. Your provider may recommend treatment with aspirin and other medicine.
Infections. Some infections of your reproductive organs, like the ovaries, uterus and cervix, may play a role in repeat miscarriages.
Harmful chemicals. If you or your partner work with certain harmful chemicals, you may be more likely to have repeat miscarriage. These chemicals include solvents, like paint thinner. If you’re worried about being around harmful chemicals, tell your health care provider.
Last reviewed: September, 2012