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Causes of Miscarriage

Though women often blame themselves after a miscarriage, they shouldn’t: the causes of miscarriage generally relate more to genetic abnormalities that prevent the fetus from developing naturally than anything the mother has done. Everyday activities such as sex, exercise and work generally have nothing to do with it. Miscarriages are common, occurring in as much as 20 percent of pregnancies, usually in the first trimester; in fact, many women who miscarry do not even know they were pregnant.

There are a number of possible reasons for miscarriage, including fetal chromosomal defects, hormonal issues or abnormalities of the uterus. However, in up to 75 percent of recurrent (meaning three or more) miscarriage, the causes of miscarriage are unknown. In many cases, because miscarriages are relatively common, and because women who have miscarriages are likely to later have healthy babies, some doctors are reticent to test for causes until a woman has had three successive miscarriages (or two successive miscarriages if the woman is older than 35), as the treatments are sometimes controversial and not well understood.

Below is a list of some of the more common causes of miscarriage that you may wish to consult with your physician about:

  • Genetic factors: Genetic or chromosomal problems are the most common cause of miscarriage in a woman’s first pregnancy loss. Generally, these problems aren’t inherited from the fetus’ parents, but occur spontaneously and by chance. They are less commonly the cause of recurrent miscarriages.
  • Anatomical factors: Abnormalities of the uterus are commonly linked to pregnancy losses in both the first and second trimesters. Congenital abnormalities include uterine septum and a double uterus. Other anatomical problems include uterine polyps, fibroids and scar tissue inside the uterine cavity.
  • Cervical incompetence: An incompetent cervix complicates roughly 1 percent of pregnancies, and often leads to rapid miscarriages between 16 and 18 weeks of gestation. Your doctor can treat this condition with a stitch to help hold the cervix closed.
  • Industrial solvents: Exposure to certain solvents, either by the pregnant woman or her partner, sometimes may cause miscarriage. Couples should discuss any chemicals in the workplace with their doctor.
  • Endocrine factors: A luteal phase defect occurs when the body secretes too little progesterone during the luteal phase of the menstrual cycle, which is thought (though this is controversial) to be a factors in some cases of recurrent miscarriage. Your doctor can test for this condition by conducting a biopsy of the lining of the uterus. Researchers have also linked maternal endocrine disorders such as uncontrolled diabetes or severe thyroid abnormalities to miscarriage.
  • Environmental factors: Smoking has been linked to recurrent miscarriage. Women who are pregnant should refrain from smoking and alcohol use. According to the American Society of Reproductive Medicine, there is some evidence that DNA abnormalities in a man’s sperm may increase the risk of miscarriage; however, how this happens is unclear.
  • Immunology: Antiphospholipid syndrome, an immune disorder, is the cause for recurrent miscarriage in as much as 15 percent of women. Women with recurrent miscarriages should be tested for lupus anticoagulant and anticardiolipin antibodies (cardiolipins are a type of phospholipids). These conditions can be treated with low-dose aspirin and heparin, which can increase blood flow to the placenta by inhibiting the tendency for clotting.

To ameliorate the risk factors for recurrent miscarriage, the American Society of Reproductive Medicine recommends a healthy lifestyle, which includes taking folic acid supplements, quitting smoking, weight control, and reducing intake of caffeine and alcohol. 

Locations for Miscarriage