1. Maternal or fetal stress: Constant stress in the mother (such as exhaustion, tension, emotional stress or abuse) appears to trigger the production of hormones that can cause contractions and premature labor. Stress in the infant (such as poor blood supply from the placenta or birth defects) can also lead to premature labor. Medical conditions in the mother, including anemia, unhealthy diet, and diabetes, may contribute to physical stress for both mother and child during pregnancy.
2. Infections: Studies suggest that premature labor is often triggered by the body's natural immune response to certain infections. Urinary tract infections, vaginal infections, and sexually transmitted infections can all lead to preterm labor. Even infections far away from the reproductive organs may contribute to premature delivery.
3. Bleeding: The uterus may bleed due to problems such as placental abruption (the placenta separates from the wall of the uterus). Bleeding triggers the release of proteins involved in blood clotting. These proteins may cause labor contractions to begin.
4. Stretching of the uterus. An overstretched uterus is a risk factor for preterm birth. This may happen when a woman is carrying two or more babies. It can also happen when there is too much amniotic fluid (polyhydramnios) or when the uterus is abnormal.
One condition that can lead to premature delivery is incompetent cervix. This means that the cervix opens too early. Doctors don't know why this occurs. For more information, read Cervical Insufficiency (Incompetent Cervix)
Because there are several reasons that may help explain why preterm labor occurs, this may explain why prematurity is so difficult to prevent. Scientists are working on ways to stop a woman's body from triggering labor before her pregnancy has reached full term. But first they must identify the women who need these treatments.
Three groups of women are at greatest risk of preterm labor and birth:
- Women who have had a previous preterm birth
- Women who are pregnant with twins, triplets or more
- Women with certain uterine or cervical abnormalities
If you have any of these three risk factors, it's especially important for you to know the signs and symptoms of preterm labor and what to do if they occur.
For more information on premature labor—including causes, risk factors, prevention, and signs of labor—click here.
January 2007
