CausesBy Mayo Clinic staff
Abnormal genes or chromosomes
Most miscarriages occur because the fetus isn't developing normally. Problems with the baby's genes or chromosomes are typically the result of errors that occur by chance as the embryo divides and grows — not problems inherited from the parents. Some examples of abnormalities include:
- Blighted ovum. Blighted ovum occurs when a fertilized egg develops a placenta and membrane but no embryo. Blighted ovum is common — the cause of about half of all miscarriages that occur in the first 12 weeks.
- Intrauterine fetal demise. In this situation the embryo is present but has died before any symptoms of pregnancy loss have occurred. This situation may also be due to genetic abnormalities within the embryo.
- Molar pregnancy. A molar pregnancy, also called gestational trophoblastic disease, is less common, occurring in about 1 in 1,000 pregnancies. It is an abnormality of the placenta caused by a problem at fertilization. In a molar pregnancy, the early placenta develops into a fast-growing mass of cysts in the uterus. This mass may or may not contain an embryo. If it does contain an embryo, the embryo will not reach maturity.
A mother's health conditions
In a few cases, a mother's health condition may lead to miscarriage. Examples include:
- Uncontrolled diabetes
- Thyroid disease
- Hormonal problems
- Uterus or cervix problems
What does NOT cause miscarriage
Routine activities such as these don't provoke a miscarriage:
- Lifting or straining
- Having sex
- Working, provided you're not exposed to harmful chemicals
- Zuccala SJ, et al. Spontaneous miscarriage. In: Ferri FF. Ferri's Clinical Advisor 2010. St. Louis, Mo.: Mosby; 2009. http://www.mdconsult.com/books/page.do?eid=4-u1.0-B978-0-323-05610-6..00028-7--sc0160&isbn=978-0-323-05610-6&type=bookPage§ionEid=4-u1.0-B978-0-323-05610-6..00028-7--sc0160&uniqId=217216664-3. Accessed Sept. 7, 2010.
- Katz VL. Spontaneous and Recurrent Abortion: Etiology, Diagnosis, Treatment. In: Katz VL, et al., eds. Comprehensive Gynecology. 5th ed. Philadelphia, Pa.: Mosby; 2007. http://www.mdconsult.com/das/book/body/217216664-7/0/1524/100.html?tocnode=53759223&fromURL=100.html. Accessed Sept. 7, 2010.
- Simpson JL, et al. Pregnancy loss. In: Gabbe, SG, et al. Obstetrics: Normal and Problem Pregnancies. 5th ed. Philadelphia, Pa.: Churchill Livingstone; 2008. http://www.mdconsult.com/das/book/body/217216664-3/0/1528/242.html?tocnode=57027393&fromURL=242.html#4-u1.0-B978-0-443-06930-7..50026-8_1154. Accessed Sept. 7, 2010.
- Early pregnancy loss: Miscarriage and moloar pregnancy.The American College of Obstetricians and Gynecologists. http://www.acog.org/publications/patient_education/bp090.cfm. Accessed Sept. 7, 2010.
- Tulandi T, et al. Spontaneous abortion: Risk factors, etiology, clinical manifestations, and diagnostic evaluation. http://www.uptodate.com/home/index.html. Accessed Sept. 7, 2010.
- Tulandi T, et al. Spontaneous abortion: Management. http://www.uptodate.com/home/index.html. Accessed Sept. 7, 2010.
- Puscheck EE, et al. The impact of male factor on recurrent pregnancy loss. Current Opinion in Obstetrics & Gynecology: 2007;19:222..
- Harms RW (expert opinion). Mayo Clinic, Rochester, Minn. Sept. 7, 2010.