Preterm labor and birth

Preterm labor (also called premature labor) is labor that begins before 37 weeks of pregnancy. Because the fetus is not fully grown at this time, it may not be able to survive outside the womb. Health care providers will often take steps to try to stop labor if it occurs before this time.

A baby born before 37 weeks of pregnancy is considered a preterm birth (or premature birth). Preterm births occur in about 12 percent of all pregnancies in the U.S. It is one of the top causes of infant death in this country.

Who is at risk for preterm labor and birth?
Health care providers currently have no way of knowing which women will experience preterm labor or deliver their babies preterm. But there are factors that place a woman at higher risk for preterm labor or birth:


 * Certain infections, such as bacterial vaginosis and trichomoniasis
 * Shortened cervix
 * Previously given birth preterm

What are the challenges to a baby born preterm?
Premature infants may face a number of health challenges, including:


 * Low birth weight
 * Breathing problems because of underdeveloped lungs
 * Underdeveloped organs or organ systems
 * Greater risk for life-threatening infections
 * Greater risk for a serious lung condition, known as respiratory distress syndrome
 * Greater risk for cerebral palsy (CP)
 * Greater risk for learning and developmental disabilities

They may need to stay in the hospital for several weeks or more, often in a neonatal intensive care unit (NICU).

What methods are used to prevent preterm delivery?
Research supported by the NICHD found that treating high-risk pregnant women (those who have previously had a spontaneous preterm baby) with a certain type of progesterone reduces the risk of another preterm delivery. The treatment worked among all ethnic groups in the study and improved outcomes for the babies. Efforts to find out whether the treatment works for other at-risk women, such as those having twins and triplets, are ongoing.

Bed rest and medications that relax the muscles in the uterus are also commonly used to try to stop preterm labor.

Researchers have found that other methods of stopping preterm labor are not as effective as once thought. For instance, NICHD-supported researchers have found that home uterine monitors are not effective for predicting or preventing preterm labor.

In addition, NICHD-funded research found that screening women who don’t show any symptoms of infection, but who have bacterial vaginosis, and treating them with antibiotics did not prevent preterm birth.