Also known as premature labor, is when a women begins having regular contractions that causes her cervix to start to open or thin out (called dilation and effacement) before reaching 37 weeks of pregnancy.
Labor beginning before 37 completed weeks of pregnancy (35 weeks after conception) is considered premature, or preterm labor. If labor cannot be stopped, a preterm birth may result. Preterm birth is the biggest single cause of infant morbidity (disease and disability) and death in the United States.
Labor that begins after 20 weeks, when the fetus is considered viable, andbefore the 37th week, when the baby is considered full-term. Prompt medicaltreatment can occasionally halt or postpone early labor, improving thebaby's chances for survival.