NEW YORK (Reuters Health) – Noninvasive uterine electromyography (EMG) identifies true preterm labor more accurately than clinical methods now in use, new research shows.

“It can therefore identify those patients who will really benefit from early institution of tocolytic therapy, transport to a hospital with facilities for neonatal intensive care, and administration of steroids,” Dr. Robert E. Garfield of St. Joseph’s Hospital and Medical Center in Phoenix and colleagues said in their report, which appeared online December 9th in the American Journal of Obstetrics & Gynecology.

With Houston-based Reproductive Research Technologies, Dr. Garfield and his colleagues have been developing a device to record EMG readings; they’re presently awaiting approval from the U.S. Food and Drug Administration. (The company was not listed as a sponsor of the current study, however.)

Obstetricians now rely on tocodynamometers, which employ strain gauges to measure contractions. Dr. Garfield told Reuters Health that his team expects the new device to someday “replace the equipment that’s now used in the clinic.”

Up to half the time, women admitted to the hospital for preterm delivery end up delivering at term, according to the article. “It’s really like a toss of the coin if you depend on clinical diagnosis,” Dr. Garfield said.

At the same time, 20% of symptomatic patients who are not diagnosed as being in true preterm labor will deliver prematurely. “This leads to unnecessary treatments, missed opportunities to improve neonatal outcome, and largely biased research of treatments,” the researchers said in their paper.

Given the changes in electrical activity within the myometrium that occur during true labor, they believed uterine EMG might help determine whether a patient is in true labor and will, or will not, deliver preterm (i.e., at less than 34 weeks).

To investigate, the researchers performed EMG in 116 women within 24 hours of hospital admission, including 20 in preterm labor, 68 in preterm nonlabor, 22 in term labor, and six in term nonlabor. Five different investigators performed the EMG tests, which lasted 30 minutes and were performed within 24 hours of hospital admission.

The 20 women in preterm labor delivered their babies within seven days; their exams showed a mean propagation velocity (PV) of 53 cm/sec, compared to 11 cm/sec in the women who delivered after seven days (P<.001). Power-spectrum (PS) peak frequencies were 0.56 Hz for the women in true preterm labor vs 0.44 Hz for women who did not deliver prematurely (P = 0.002). No other measured parameter was different between the preterm labor and preterm nonlabor groups. For term patients, PV was 31 cm/sex for the 22 patients in labor, compared to 11 cm/sec for women not in labor. Combining PV and PS peak frequency predicted preterm delivery within one week with an area under the curve (AUC) of 0.96, the researchers found. AUC was 0.72 for Bishop score, 0.67 for contractions, and 0.54 for cervical length. “In the case of low PV and peak frequency values, it therefore stands to reason that it would be safe not to admit, treat, or transfer the patient, regardless of the presence of contractions on TOCO and regardless of digital cervical exam and transvaginal cervical length results because all the changes in the myometrium required for labor are not yet fully established,” the researchers state. They conclude: “It would be useful to do a prospective clinical trial to confirm our results. They may be extremely important clinically but could also lead to more reliable analyses of treatments and eventually to more effective interventions to prevent preterm births.” Reference:
Noninvasive uterine electromyography for prediction of preterm delivery

Am J Obstet Gynecol 2010.