Can preterm labor be prevented?

Preterm labor is defined as labor (rhythmic contractions accompanied by progressive dilatation of the cervix) that takes place before 37 weeks of pregnancy. Giving birth before 37 weeks can be associated with risks for the baby, including death—but clearly much depends on exactly when delivery happens. Delivery at 36.5 weeks counts as preterm, but is usually not of consequence or concern; delivery at 24 weeks is perilous, and when such preterm babies survive they almost always have significant long-term handicaps. 

Like with so many things in medicine, the biggest risk for preterm labor and delivery is having had it happen before. Other risk factors include: carrying multiples, being under 18 years old or older 40 years old, a lack of prenatal care, some bacterial infections, and smoking, drinking alcohol, or using drugs during pregnancy, among others. Women who have delivered preterm before are at an approximately 25% risk of having another preterm birth, especially if there are no important changes between the pregnancies (i.e. they haven't stopped smoking.

Predicting preterm labor

Preterm labor is not a very predictable problem: Many women with some of the above noted risks will not deliver preterm and, conversely, about half of women who go into preterm labor have no risk factors for it. In recent years it has become evident that women who have cervixes that appear shorter than average when imaged on ultrasounds in the second and early third trimesters are at increased risk for preterm delivery. But, here again, the test is not a perfect or even very good predictor: many women with a shorter cervix will deliver at term and the measurement does not readily distinguish those who will deliver preterm at 36.5 weeks from those who will deliver at 24.5 weeks.

Regardless of these challenges, doctors and other researchers are studying potential interventions that might decrease the risk of women with short cervixes delivering early.  I hope that in the coming years we'll have a drug or other treatment to offer these women.

No other test is, to my knowledge, clinically useful in the prediction of preterm labor and delivery. This includes the fetal fibronectin test, which measures certain proteins in cervical and vaginal secretions. While fetal fibronectin can sometimes be a useful test when performed on women who present with symptoms of preterm labor (e.g. contractions before term), it is not a good screening test for asymptomatic women.

Researchers have studied the use of home monitors to detect contractions in women at risk for preterm labor and delivery, but such monitoring has not been shown to be helpful and is not something I or any of my colleagues use.

Treating potential preterm labor

One of the most important things pregnant women can do is understand the symptoms of preterm labor and report them promptly if they arise. If you have pains, cramps, pressures or tightenings centered on the abdomen, pelvis, or back that last approximately 30-60 second and come and go with a rhythm of more than once every 10-15 minutes, you should notify your provider. This advice is especially true if the pains are becoming more frequent or more intense, persist in spite of lying down or changing position or activity, or are accompanied by vaginal bleeding or change in vaginal discharge.

Your doctor may tell you to rest on your left side, drink water or juice, or to go to his or her office or the emergency room.

If you and your provider determine that you are in preterm labor, you will likely be admitted to the hospital for observation and, depending on how early you are in pregnancy, may be treated with medications to try to quiet the contractions and delay delivery. In general such medications don't delay delivery for long, but even a few days can make a difference at less than 34 weeks, as the delay can allow for treatment with medications (steroids such as betamethasone or dexamethasone) that have been shown to help babies destined to be born preterm. If you are found to have a bacterial infection that is causing the preterm labor, you may be given an antibiotic to treat that infection.

Women who go into preterm labor but who don't deliver (as much a result of destiny as any particular medication or treatment) are often told to stay on bed rest or limit their activity until they get closer to 34-36 weeks of pregnancy. Finding strong evidence to support recommendations for bed rest is difficult, however. This lack of evidence is due, at least in part, to the fact that bed rest has been what doctors have recommended for so long that patients and providers would be reluctant to be a part of any study that made one group of women get regular activity.

Do you have questions about preventing or treating preterm labor? 

Jeffrey Ecker, M.D., is an attending perinatologist (high-risk obstetrician) at Massachusetts General Hospital. He is also an Associate Professor at Harvard Medical School.

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