It’s normal for women to have some uterine contractions throughout pregnancy. Often, a woman is unaware of these contractions, but at other times they can be painful and regular and seem much like labor. It may be difficult, therefore, 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 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 (external uterine monitoring). A belt is wrapped around your waist and attached to a machine called a tocodynamometer. Although this is usually done in a doctor's office or hospital, it can also be done at home.

To monitor your contractions at home, you rent equipment to trace your contractions. Sit in a restful position and place the band attached to the tocodynamometer around your abdomen. The machine records your contractions and the data is transmitted by telephone 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.

The nurses may also contact you by phone once or twice a day to see how you are feeling. If you report any problems, the nurse contacts your doctor immediately.

Uterine monitoring is based on the idea that the frequency of contractions per hour increases as a woman gets closer in delivery.

If the machine measures four or less contractions per hour, you are 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 you are not changing your cervix, you are not in preterm labor — even if you can feel your contractions.

Early studies suggested that home monitoring could prevent early delivery, but more recent studies have shown that home uterine activity monitoring is not useful. In 1998, a large study of more than 2,400 high-risk pregnant women — including 844 women with twins — was published in the Journal of Medicine.

In this study the authors sought to determine whether using the HUAM machine in addition to daily nursing contact could reduce the rate of spontaneous preterm delivery for women less than 35 weeks pregnant. In addition, the study sought to determine whether daily nursing contact, with or without the monitoring machine, would be more effective than weekly nursing contact.

Three groups of women were studied:

  • women who had daily contact with nurses and monitors
  • women who had daily contact with nurses but no monitor
  • women who had weekly contact with nurses but no monitor

All women received detailed education on preventing preterm delivery. They were asked to keep a daily log of symptoms of labor and the number of contractions they could detect without a machine, simply by placing their hands firmly on their abdomen. The regular doctors and nurses caring for these women didn’t know which group the women were in.

The researchers found that using monitors in addition to daily contact with the nurse didn’t improve early detection of preterm labor or delivery. Daily contact, instead of weekly contact, also didn’t improve early detection.

Researchers concluded that the similar outcomes among the three groups were due to three factors.

  1. All women received the same standardized 45-minute educational program.
  2. The daily log encouraged women to be attentive to contractions and other signs of labor.
  3. Nurses encouraged women to get help right away if preterm labor was suspected. These results can be applied to well-educated, middle class women with high-risk pregnancies, since women from these groups were the ones studied. It’s unclear whether studying other groups of women would produce similar results.

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

In general, however, scientific studies have shown that home monitoring devices are not helpful. If your doctor recommends this treatment, ask why they think 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.