If labor occurs before a pregnancy reaches its 37th completed week (full term is normally 40 weeks), it's called premature labor, or preterm labor.
The World Health Organization defines preterm labor as the onset of contractions of the uterus before the 37th completed week of pregnancy that are:
Palpable (that can be felt by a health professional)
If there is also progressive effacement (shortening) and dilation (opening) of the cervix (the neck of the uterus), preterm labor has begun.
Just as normal labor differs in intensity from one woman to another, so do the contractions of premature labor. Some women do not have painful contractions, but describe being "uncomfortable" or merely feeling "as if something isn't right." If you think you might be in preterm labor, trust your instincts and contact your health care provider for a complete exam.
What Happens During Labor
The uterus is a muscle. During labor, it contracts, causing the cervix to shorten and open so that the baby can be born.
As labor progresses, the contractions become more frequent, stronger, and more regular.
Eventually the cervix opens fully, allowing delivery to take place.
When contractions cause the cervix to begin to open prior to the 37th week of pregnancy, this is premature labor.
Nice To Know:
During a normal pregnancy, the uterus contracts and hardens from time to time, preparing for that time when it will push the baby into the birth canal.
These normal contractions, called Braxton Hicks contractions, can be felt by pressing the fingertips on the abdomen as it becomes rounded and hard.
Braxton Hicks contractions are harmless and do not signify the onset of labor.
Facts About Premature Labor
About 8% of all deliveries are preterm. Premature labor is responsible for about 75% of stillbirths and deaths of babies in the first 7 days of life.
Despite improved technology and skill of neonatal pediatricians, about 10% of those babies who survive (usually the most immature) will suffer some degree of lasting physical or mental handicap.
Most cases of premature labor can be treated to allow the baby to become more mature in the uterus.