Tocolytics are medicines that are used to slow or stop the contractions of a woman’s uterus during pregnancy. They are typically given to women who are in preterm labor to try to delay birth for 1 to 2 days.

This delay may be needed for a variety of medical reasons, such as:

• To allow time for a fetus’s lungs to mature after corticosteroid treatment.
• To prevent labor until specialized care is obtained that either the mother or fetus is expected to need.
• To relax the mother’s uterine muscles before trying to turn a breech fetus to the head-down position (external cephalic version).
• To reduce the stress on a baby who has a low heart rate or other problem.

Examples of tocolytics include terbutaline, magnesium sulfate, nifedipine, and indomethacin.