Font Size
A
A
A

Preterm Labor


Topic Overview

Preterm labor occurs during pregnancy when the uterus starts to contract before the 37th week of pregnancy, causing the cervix to open (dilate) and thin (efface).

The length of a normal pregnancy is 37 to 42 weeks, measured from the date of the mother's last menstrual period.

Early symptoms of preterm labor often are hard to diagnose. The uterus normally begins to contract around the 20th week of pregnancy. These early contractions (Braxton Hicks contractions) do not dilate or efface the cervix but help prepare the uterus and fetus for labor. These contractions can be mistaken for preterm labor.

Preterm labor is diagnosed in a woman who is 20 to 37 weeks pregnant and has regular uterine contractions. This means 4 or more in 20 minutes, or about 8 or more in 1 hour.

Before 20 weeks, preterm labor that leads to delivery is considered a miscarriage (spontaneous abortion).

Related Information

Credits

ByHealthwise Staff
Primary Medical ReviewerWilliam H. Blahd, Jr., MD, FACEP - Emergency Medicine
Specialist Medical ReviewerDavid Messenger, MD
Last RevisedJune 26, 2010

eMedicineHealth Medical Reference from Healthwise

This information does not replace the advice of a doctor. Healthwise disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. How this information was developed to help you make better health decisions.

To learn more visit Healthwise.org

© 1995-2012 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.






Medical Dictionary