Most women spontaneously start labor within one week of rupture of membranes. In certain circumstances, your doctor may recommend medications to stop or delay the labor. The process of inhibiting labor is called tocolysis and the drugs used to inhibit labor are referred to as tocolytic agents.

Tocolytic medications come in several different classes:

  • beta-mimetics (terbutaline);
  • magnesium sulfate;
  • calcium channel blockers (nifedipine); and
  • non-steroidal anti-inflammatory drugs (NSAIDs), such as indomethacin.

General information about these drugs is given below.

Why Use Tocolytic Medications?

Tocolytic medications can delay delivery for at least a few days. This may not seem like a long time, but it can be helpful in the following two ways:

  • delaying delivery may give your baby extra time for development. If your doctor gives you steroids, tocolytics can provide time for the steroids to work; and
  • your doctor may try to prevent delivery while you are being transferred to a hospital with better facilities and services for preterm babies.

What Kind Of Tocolytic Medication Should Be Used?

There is no data showing that one drug is consistently better than another. Terbutaline is the drug most often given first. For women at high risk, magnesium sulfate (given by IV) is usually the drug of choice.

At What Point During My Pregnancy Can I Take Tocolytic Medications?

Tocolytic medications should not be given before 17 weeks of pregnancy, and many doctors will not use them before 23 to 24 weeks. Most doctors will avoid giving tocolytics after a woman has reached her 34th week of pregnancy, but some doctors will begin tocolytics as late as 36 weeks.

How Long Should Tocolytic Medications Be Continued?

Since contractions can be a sign of uterine infection that may make continuing the pregnancy unsafe for you and your baby, most experts advise against the long-term use of tocolytic therapy. In fact, studies have shown no benefit of long-term use of these drugs if you have PPROM. Prolonging pregnancy more than 48 hours after PPROM may not be a good idea, and it is usually not possible.

Who Should Not Use Tocolytic Medications?

Women should not use tocolytic medications when the risks of using the medications outweigh the benefits. This includes women with severe preeclampsia or eclampsia (high blood pressure that develops during pregnancy), severe bleeding (hemorrhage), or infection in the womb (chorioamnionitis).

In other situations, a doctor may be cautious about using tocolytic medications, but may prescribe them because the benefits outweigh the risks. These situations may include when the mother has:

  • mild preeclampsia;
  • relatively stable bleeding during the second or third trimester;
  • serious medical conditions; or
  • a cervix that has already dilated 4 to 6 cm or more.

Or when the baby has:

  • an abnormal heart rate (as shown on the fetal heart monitor) or
  • slow growth.