Noninvasive uterine electromyography for prediction of preterm delivery

Abstract

Objective: Power spectrum (PS) of uterine electromyography (EMG) can identify true labor. EMG propagation velocity (PV) to diagnose labor has not been reported. The objective was to compare uterine EMG against current methods to predict preterm delivery.

Study design: EMG was recorded in 116 patients (preterm labor, n = 20; preterm nonlabor, n = 68; term labor, n = 22; term nonlabor, n = 6). A Student t test was used to compare EMG values for labor vs nonlabor (P < .05, significant). Predictive values of EMG, Bishop score, contractions on tocogram, and transvaginal cervical length were calculated using receiver-operator characteristics analysis.

Results: PV was higher in preterm and term labor compared with nonlabor (P < .001). Combined PV and PS peak frequency predicted preterm delivery within 7 days with area under the curve (AUC) of 0.96. Bishop score, contractions, and cervical length had an AUC of 0.72, 0.67, and 0.54.

Conclusion: Uterine EMG PV and PS peak frequency more accurately identify true preterm labor than clinical methods.

Copyright © 2011 Mosby, Inc. All rights reserved.

Figures

Figure 1

Flow sheet diagram for better visualization of study groups.

Figure 2

Propagation velocity of electromyographic (EMG) signals was calculated from the time difference of the signal arrival at adjacent electrodes (t). Top trace shows a sample recording from two electrode pairs (channels 1&2). Note the excellent temporal correspondence between EMG and mechanical contractile events (measured by TOCO). Bottom trace shows the expanded EMG burst, with the individual voltage peaks clearly distinguishable.

Figure 3

Comparison of uterine electromyography propagation velocity values for preterm patients delivering within 7 days of measurement vs. those delivering more than 7 days from measurement. Means and standard deviations shown; * represents statistical significance (P

Figure 4

Comparison of uterine electromyography power spectrum (PS) peak frequency values for preterm patients delivering within 7 days of measurement vs. those delivering more than 7 days from measurement. Means and standard deviations shown; * represents statistical significance (P

Figure 5

Uterine electromyography propagation velocity (PV) + power spectrum peak frequency (PS) increases as the measurement-to-delivery interval decreases. □ Preterm labor – delivery ≤ 7 days from the measurement; ● delivery > 7 days from the measurement.

Figure 6

Comparison of receiver-operating-characteristics (ROC) curves for uterine electromyography (EMG) parameters (rescaled sum of propagation velocity [PV] and power spectrum [PS] peak frequency) and currently used clinical methods to predict preterm delivery within 7 days.

Figure 7

Propagation velocity was significantly higher (P 0.05). Data are presented as box plots and not vertical bar charts due to non-normal distribution in term labor group. Term Labor – delivery within 24 hours; Term Non-labor – delivery after 24 hours; Preterm Labor – delivery within 7 days; Preterm Non-labor – delivery after 7 days.* represents statistical significance.