Preterm Labor or Preterm Contractions?

What's the difference?

Preterm Labor or Preterm Contractions?

What's the difference between preterm labor and preterm contractions? It's all in the cervix, baby. If it changes, it's labor. If it doesn't, it's annoying. Sarah, 34 weeks pregnant with her first baby, has had contractions for a few weeks. They're not painful and yet there are enough of them that she wisely headed to the hospital for evaluation.

Virtually all women have contractions in the last trimester. The baby is putting on weight and the uterus stretches and tightens as it adjusts to its new size. Many women don't feel them, but some feel every single one. These late-pregnancy contractions are usually normal, harmless and in a way, healthy. The uterus is exercising to get ready for the big day. They work to position the baby properly and get the cervix prepared for labor. Sort of like training for a marathon.

How do you know when they're normal and when they're not?

You don't. Only your labor and delivery department or doctor/midwife can tell you. Sometimes, contractions are a sign of something else going on like a urinary tract infection or gastrointestinal virus. If you're feeling more than the occasional contraction, it's smart to call your doctor/midwife and let them decide whether you need to be checked out. It turned out Sarah had a urinary tract infection and needed a course of antibiotics to clear it up. The only symptom she had was contractions.

Contraction Action: The lowdown on different types and what they mean

We see patients every day in labor and delivery with preterm contractions. We put them on the fetal heart monitor and watch to see what kind of pattern they make. Are they regular and frequent or irregular and rare? We may do a swab of the cervix and vagina to test for a protein called fetal fibronectin. The March of Dimes explains, "Fetal fibronectin (fFN) is a protein produced during pregnancy and functions as a biological glue, attaching the fetal sac to the uterine lining. The presence of fFN during weeks 24-34 of a high-risk pregnancy, along with symptoms of labor, suggests that the "glue" may be disintegrating ahead of schedule and alerts doctors to a possibility of preterm delivery."

If there is no fetal fibronectin present (a negative test), it's not likely these contractions will lead to preterm labor. This may help Mom avoid unnecessary medical interventions like hospitalization, prolonged bed rest and drugs.

After the fFn test is done, we'll probably check her cervix and see if it is dilating. If this is a first baby, we'll expect it to be un-dilated. If it's a second (or more), it's not uncommon to be a little dilated during the last weeks of pregnancy. We might have Mom hang out in L&D for a few hours while we watch contractions and see if the cervix changes. If it doesn't change and contractions aren't too frequent or painful, it's probably not labor.

We may try to stop contractions by giving her a lot of water to drink. Dehydration sometimes causes contractions. If they continue, some doctors will prescribe medications to stop them. Sarah was given Terbutaline to take at home in pill form when contractions kicked up. It relaxes smooth muscle (like the uterus), and hopefully decreases contractions. 

Terbutaline is prescribed less frequently than it was a decade ago because its effectiveness is debatable and it causes some unpleasant side effects. It often makes Mom's heart race, gives her the jitters and it crosses the placenta. Some babies develop symptoms of gestational diabetes after exposure to Terbutaline and may require frequent glucose monitoring after birth. Some doctors prescribe it and some don't. Some studies say it doesn't really make any long-term difference in preventing preterm labor and the side effects aren't worth it. There are other drugs that may be more effective if Mom really is experiencing preterm labor.

Within a week, Sarah will cross the 35 week mark where delivering a baby is relatively safe. Closer to her due date is better but if a baby is determined to make an early entrance, 35 weeks is good enough. While we certainly don't want any woman to take contractions for granted, it's reassuring to know that most of the time, they don't mean labor's coming. They just mean the uterus is thinking about it.

Jeanne Faulkner, R.N., lives in Portland, Oregon with her husband and five children. Got a question for Jeanne? E-mail it to

This Fit Pregnancy blog is intended for educational purposes only. It is not intended to replace medical advice from your physician. Before initiating any exercise program, diet or treatment provided by Fit Pregnancy, you should seek medical advice from your primary caregiver.


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