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Uterine-Contraction Monitoring Does Not Help Predict Preterm Delivery

In this observational study, assessment of uterine-contraction frequency was not useful for predicting preterm labor in high-risk women with singleton pregnancies.

Randomized clinical trials have not indicated that monitoring uterine contractions predicts preterm delivery; however, many obstetricians continue to use such testing in ambulatory patients who are at high risk for preterm labor. In addition, other approaches to predicting preterm labor have been advocated. The authors of this NIH-funded observational study assessed the use of the following parameters as predictors of preterm delivery: frequency of uterine contractions, condition of the cervix, and presence or absence of cervicovaginal fibronectin (a fetal-membrane protein).

Women who were at high risk for preterm labor (all singleton pregnancies) were enrolled between 1994 and 1996 at 11 maternal-fetal medicine research units. Antepartum women without risk factors for preterm labor were also enrolled. All 306 participants were screened for eligibility before 22 weeks' gestation. Mean age was 26, mean parity was 1.8, 60% of the women were black, and 26% smoked cigarettes. Participants used a monitor at home to record uterine activity during 2 daily, 1-hour sessions at least 2 hours apart -- 1 session between 4 AM and 4 PM and the other between 4 PM and 4 AM. In addition, the women were evaluated every 2 to 3 weeks at outpatient visits. Because the frequency of uterine contractions was not found to be related to the historic risk for preterm labor, data from the high- and low-risk women were combined.

Women who delivered their infants before 35 weeks' gestation had more contractions than did women who delivered at or after 35 weeks. However, the sensitivity and positive predictive value of contraction frequency in identifying women at increased risk for preterm labor was poor. None of the other assessments were found to have good sensitivity or a high positive predictive value.

Comment: In the ongoing quest to prevent preterm birth, many approaches for detecting and suppressing early uterine contractions have been recommended. Consistent with early reports, this study does not support the use of ambulatory uterine-contraction monitoring to identify women who are likely to have preterm delivery. Likewise, assessment of the cervix or fetal fibronectin did not prove useful. As an editorialist indicates, we have a long way to go in developing strategies to predict or suppress preterm labor.

— Andrew M. Kaunitz, MD

Published in Journal Watch Women's Health March 5, 2002

Citation(s):

Iams JD et al. Frequency of uterine contractions and the risk of spontaneous preterm delivery. N Engl J Med 2002 Jan 24; 346:250-5.

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Lockwood CJ. Predicting premature delivery -- No easy task. N Engl J Med 2002 Jan 24; 346:282-4.

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• Medline abstract (Free)