What is a miscarriage?

A miscarriage, also called a spontaneous abortion, is the spontaneous ending of a pregnancy About 1/3 to 1/2 of all pregnancies end in miscarriage before a woman misses a menstrual period or even knows she is pregnant. About 10-20% of women who know they are pregnant will miscarry.

A miscarriage is most likely to occur within the first 3 months of pregnancy, before 20 weeks’ gestation. Only 1% of miscarriages occur after 20 weeks’ gestation. These are termed late miscarriages.

What are the risk factors for a miscarriage?

A risk factor is a trait or behavior that increases a person’s chance of developing a disease or predisposes a person to a certain condition. Risk factors for miscarriage include:

  • Maternal age: Studies show that the risk of miscarriage is 12% to 15% for women in their 20s and rises to about 25% for women at age 40. The increased incidence of chromosomal abnormalities contributes to the age-related risk of miscarriage.
  • Certain health conditions in the mother as listed in the section, "What causes miscarriage?"

What causes miscarriage?

About half of all miscarriages that occur in the first trimester are caused by chromosomal abnormalities — which might be hereditary or spontaneous — in the father’s sperm or the mother’s egg. Chromosomes are tiny structures inside the cells of the body that carry many genes, the basic units of heredity.

Genes determine all of a person’s physical attributes, such as sex, hair and eye color, and blood type. Most chromosomal problems occur by chance and are not related to the mother’s or father’s health.

Miscarriages are also caused by a variety of unknown and known factors, such as:

  • Infection.
  • Exposure to environmental and workplace hazards such as high levels of radiation or toxic agents.
  • Hormonal irregularities.
  • Improper inplantation of fertilized egg in the uterine lining.
  • Maternal age.
  • Uterine abnormalities.
  • Incompetent cervix. (The cervix begins to widen and open too early, in the middle of pregnancy, without signs of pain or labor.)
  • Lifestyle factors such as smoking, drinking alcohol, or using illegal drugs.
  • Disorders of the immune system including lupus, an autoimmune disease.
  • Severe kidney disease.
  • Congenital heart disease.
  • Diabetes that is not controlled.
  • Thyroid disease.
  • Radiation.
  • Certain medicines, such as the acne drug Accutane®.
  • Severe malnutrition.
  • Group B beta strep.

Note: There is no proof that stress, or physical or sexual activity causes miscarriage.

Sometimes, treatment of a mother’s illness can improve the chances for a successful pregnancy.

What are the symptoms of a miscarriage?

Symptoms of a miscarriage include:

If you are experiencing the symptoms listed above, contact your healthcare provider right away. He or she will tell you to come in to the office or go to the emergency room.

What are some of the symptoms after a miscarriage?

Spotting and mild discomfort are common symptoms after a miscarriage. If you have heavy bleeding, fever, chills, or pain, contact your healthcare provider immediately as these may be signs of an infection.

Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy