Preterm labor is regular contractions that result in cervical changes before 37 weeks of pregnancy.

Overview and Symptoms

Preterm labor is categorized by regular contractions before 37 weeks of pregnancy that result in cervical change, such as dilation (opening of the cervix) or effacement (thinning of the cervix) in preparation for birth. In the United States, approximately 12% of births occur before term.

Symptoms of preterm labor are similar to those of labor – back pain, changes in vaginal discharge, bleeding or a leaking of fluid.

The cause of preterm labor is unknown, although risk factors include:

  • A prior pregnancy with preterm labor or preterm delivery
  • Cervical shortening
  • Multiple gestations
  • Vaginal bleeding
  • Underlying medical complications
  • Smoking


Your doctor will perform a pelvic exam to see if there are any cervical changes that can be detected physically. An electronic monitor will be used to assess your contraction pattern as well as your baby’s well-being.

Often, we will admit you to the hospital for observation. You may be given steroids and other medications to help speed up fetus development while slowing down labor.

Maternal-Fetal Medicine

The Center for Maternal-Fetal Medicine at BIDMC provides extraordinary care for pregnancies with potential complications to mother or baby.

Learn More