Preterm Labor - Medications

Medications

If your contractions are causing changes in your cervix (preterm labor), or you have signs of infection or preterm premature rupture of membranes (pPROM), you may be treated with one or more medications, including:

• Antibiotics, to prevent or treat infection. Antibiotic treatment does not always eliminate infection. But it is often effective in preventing infection when the amniotic sac has ruptured (pPROM) and risk of infection is high.¹⁷ Antibiotics can also delay delivery after pPROM.³
• Medications (antenatal corticosteroids) to speed up fetal lung development if birth is anticipated between the 24th and 34th weeks of pregnancy.
• Tocolytic medications, to slow down contractions and try to delay labor for a day or two.

Tocolytic treatment is more likely to be successful when preterm labor is recognized and treated right away, before membranes have ruptured or the cervix has effaced and dilated beyond 4 cm.¹ Delaying labor even for a short time can allow you to be:

• Transported to a medical center that has a neonatal intensive care unit (NICU).
• Given antenatal corticosteroids, which take a minimum of 48 hours to fully benefit a fetus's lungs. However, 24 hours does provide some benefit.

Medication Choices

Antibiotic medication is chosen by your doctor or nurse-midwife based on the type of infection present.

Antenatal corticosteroids (betamethasone or dexamethasone) help prepare the fetus's lungs for preterm birth.

Tocolytic medications that are used to stop preterm labor include:

• Ritodrine or terbutaline.
• Indomethacin.
• Nifedipine.
• Magnesium sulfate. In the United States, this medication is used less commonly than in the past.

What To Think About

If you have had a spontaneous preterm birth before, you are probably at high risk for another preterm labor. This might make you a possible candidate for weekly progesterone for preventing preterm labor and delivery. This is a promising new approach, though it isn't yet widely used in all areas of the country. Also, the type of progesterone used, 17 alpha-hydroxyprogesterone caproate, is not widely available. No fetal or newborn harm has been observed, though long-term research has not been done to rule out long-term side effects.¹⁶

A single course of antenatal corticosteroid treatment, used to prepare the fetus's lungs for birth, is considered to be the least risky, most effective treatment available for avoiding the most common preterm fetal complications at birth.² It is standard procedure to give corticosteroid injections to most women before preterm birth, especially for pregnancies at 24 to 34 weeks of gestation.

If you test positive for infection, you will be treated with an antibiotic during pregnancy or labor in an attempt to prevent infection in your newborn. This is why women with preterm premature rupture of membranes (pPROM) are screened for group B strep (GBS).

Antibiotic treatment for preterm labor is:

• Beneficial for women with pPROM. Antibiotics may delay labor and reduce risk of newborn infection.³
• Not recommended for women with intact membranes and no evidence of infection.¹⁸
• Continued for 5 days in women with GBS.
• Used for women whose GBS diagnosis is unknown.

Tocolytic medications are used to delay preterm birth for a day or more so that antenatal corticosteroids can work. Tocolytics cause side effects that may require stopping treatment or trying a different tocolytic medication. Side effects are closely monitored and rarely cause permanent damage to the mother or fetus but can be unpleasant for the mother (see the specific medications). During tocolytic treatment, a woman is usually on continuous fetal monitoring and her vital signs are checked frequently.

Considerations before using tocolytics include your and your fetus's health, how far your labor has progressed, whether your membranes have ruptured, and whether you have an infection. Certain tocolytic medications can be dangerous when a fetus is showing signs of distress or for women with certain health conditions (such as heart problems, severe preeclampsia, or poorly controlled diabetes or high blood pressure). Magnesium sulfate is being used less than it was used in the past. Studies show it does not stop preterm labor and it may cause complications for both mother and baby.¹⁹

Tocolytics aren't likely to work at all after membranes have ruptured or the cervix is well effaced and dilated at or beyond 4 cm.¹