It’s normal for women to have some uterine contractions throughout pregnancy. Often, a woman is unaware of these contractions, but at other times the contractions can be painful and regular and seem much like labor.

It may be difficult to distinguish between contractions that are a normal part of pregnancy and those that may signal the onset of preterm labor.

To differentiate normal contractions from preterm labor, your doctor may suggest monitoring your contractions. Your doctor does not want you to go into labor before 39 weeks of pregnancy. Babies born early are considered premature and can have significant health issues.

The further along your pregnancy is, the less complications arise. Contractions may be a sign of premature labor. Your doctor may also order a transvaginal ultrasound to see if the contractions are producing changes in your cervix that might signify the start of labor.

Uterine contractions can be monitored externally, without inserting instruments into your uterus. This is called external uterine monitoring.

The monitoring is usually performed in a doctor’s office or hospital. A nurse will wrap a belt around your waist and attach it to a machine called a tocodynamometer. The machine records the frequency and length of your contractions.

Your doctor may also recommend monitoring your contractions at home. They will instruct you to sit in a restful position and place the band attached to the tocodynamometer around your abdomen. The machine records your contractions and transmits the data to a central viewing station, usually in a hospital or clinic.

Nurses there assess the data and prepare a detailed report about the contractions for your doctor. Nurses can also answer questions on how to apply the band and care for yourself.

The nurses may also contact you by phone once or twice a day to see how you’re feeling. If you report any problems or if the monitoring shows changes, the nurse will contact your doctor immediately.

Uterine monitoring is based on the idea that the frequency of contractions per hour increases as a woman gets closer to delivery. As labor progresses, contractions get longer, harder, and stronger.

If the machine measures four or less contractions per hour, you’re probably not in labor. If your contractions are more frequent, your doctor performs a cervical ultrasound or pelvic exam to confirm the diagnosis of preterm labor.

It’s important to realize that if your contractions aren’t changing your cervix, you’re not in preterm labor — even if you can feel the contractions. Your doctor may suggest rest and drinking extra fluids since even mild dehydration can induce contractions.

Early studies suggested that home uterine activity monitoring (HUAM) could prevent early delivery, but more recent studies have shown that HUAM is not useful.

Some researchers speculate that uterine monitoring could be helpful in special circumstances. For example, if a woman has a history of cervical insufficiency, and has a positive fetal fibronectin test, then increasing contractions on a home monitor might signal that she is at risk of delivering soon.

A Cochrane Review pointed out that there needs to be more research on the effectiveness of home monitoring in preventing preterm birth. Not enough large studies have been done to know if their use helps reduce preterm delivery.

For women who live far away from the hospital, this could help them decide when to go to their hospital.

In general, however, studies have shown that home monitoring devices are not consistently helpful. If your doctor recommends this treatment, be sure you understand why it would be beneficial in your particular case.

You may also need to get special approval from your insurance company in order to qualify for this service.