Preterm Labor

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 medicines, including:

• Antibiotics, to prevent or treat infection. Antibiotic treatment does not always get rid of infection. But it often prevents infection when the amniotic sac has ruptured (pPROM) and can also delay delivery after pPROM.²
• Medicines (antenatal corticosteroids) to speed up fetal lung development if birth is anticipated between the 24th and 34th weeks of pregnancy.
• Tocolytic medicines, to slow down contractions and try to delay labor for a day or two.

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. Even 24 hours provides some benefit.

Medication Choices

Antibiotic medicine 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 medicines that are used to stop preterm labor include:

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

What To Think About

If you have had a spontaneous preterm birth in the past, 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.⁹

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. 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.²
• Used for women whose GBS diagnosis is unknown. Then if a GBS test is negative, the antibiotic may be stopped.
• Not recommended for women with intact membranes and no evidence of infection.

Tocolytic medicines 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 medicine. Side effects are closely monitored and rarely cause permanent damage to the mother or fetus but can be unpleasant for the mother (see information on the specific medicines). During tocolytic treatment, a woman is usually on continuous fetal monitoring and her vital signs are checked often.

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 medicines can be dangerous when a fetus is showing signs of distress or for women with certain health conditions (such as heart problems, severe pre-eclampsia, 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.¹⁰

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Author:	Sandy Jocoy, RN	Last Updated: January 14, 2009
Medical Review:	Sarah Marshall, MD - Family Medicine Deborah A. Penava, BA, MD, FRCSC, MPH - Obstetrics and Gynecology
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