Research www.AJOG.org OBSTETRICS A comparison of surface acquired uterine electromyography and intrauterine pressure catheter to assess uterine activity Gabi Haran, MD; Michal Elbaz, MD; Moshe D. Fejgin, MD; Tal Biron-Shental, MD OBJECTIVE: Intrauterine pressure catheter (IUPC) is the primary device RESULTS: The correlation of the frequency, intensity, and tone of con- used to evaluate uterine activity. In contrast to the IUPC, electrical uter- tractions between uterine electromyography and IUPC was strong with ine myography (EUM) enables noninvasive measurement of frequency, significant r values of 0.808-1 (P Ͻ .0001). intensity, and tone of contractions. The aim of this study was to deter- mine the accuracy of EUM compared to IUPC. CONCLUSION: Electrical uterine electromyography yields information STUDY DESIGN: EUM measured myometrial electrical activity using a about uterine contractility comparable to that obtained with IUPC. multichannel amplifier and a noninvasive position sensor. In all, 47 women in labor were monitored simultaneously with an IUPC and EUM. We compared the frequency, intensity, and tone of uterine contractions Key words: contractions, intrauterine pressure catheter, myometrial between the methods. electrical activity Cite this article as: Haran G, Elbaz M, Fejgin MD, et al. A comparison of surface acquired uterine electromyography and intrauterine pressure catheter to assess uterine activity. Am J Obstet Gynecol 2012;206:412.e1-5. onitoring uterine activity during dynamometry is limited by the thickness of clinical trial of internal and external Mlabor is indicated for evaluating the abdominal wall and by its position rel- monitoring did not show any differ- labor progress and the diagnosis of uter- ative to the uterus.4,5 ence in the rate of operative deliveries ine tachysystole, which poses a potential The intrauterine pressure catheter or of adverse neonatal outcomes.12-14 risk of fetal distress.1-3 (IUPC) is considered to be the gold Myometrial activity resulting in con- Tocodynamometry has long been the standard for monitoring uterine con- tractions is the result of molecular changes most common method for assessing uter- tractions as it enables assessment of that lead to increased coupling and excitabil- ine contractility during labor. Although both the frequency and the intensity of ity of cells.15-19 Electrical activity of the myo- this method has no complications and en- contractions more accurately than to- metrium can be monitored noninvasively 6-8 ables measurement of the frequency and codynamometry. However, IUPC by uterine electromyography (EMG).19-21 duration of contractions, its major limita- requires ruptured membranes prior to Electrical uterine myography (EUM) tion is the inability to assess the intensity of catheter insertion; therefore, its use is monitoring uses an EMG monitor with 9 uterine contractions, which is crucial for limited. In addition, this invasive electrodes that are placed on the maternal labor management. The accuracy of toco- method carries risks of placental and abdominal surface to evaluate uterine con- fetal damage, infection, and uterine tractions. Not only does EUM enable non- perforation.9-11 From the Department of Obstetrics and invasive evaluation of the beginning, time The American College of Obstetricians Gynecology, Maternal Fetal Unit, Meir Medical to peak, duration and frequency of and Gynecologists and the Society of Ob- Center, Kfar Saba, affiliated with the Sackler uterine contractions, it also evaluates School of Medicine, Tel Aviv University, Tel stetricians and Gynecologists of Canada Aviv, Israel. recommend the use of IUPC in selected their intensity. Furthermore, since it is Received Aug. 7, 2011; revised Oct. 28, 2011; circumstances, such as maternal obesity or noninvasive and does not require rup- accepted Dec. 15, 2011. limited response to oxytocin. The theory tured membranes, it can be used as a M.D.F. is an unpaid professional adviser to OB behind these recommendations is that diagnostic tool for uterine contrac- Tools, Yokne’am, Israel. The other authors tions in suspected preterm labor. It report no conflict of interest. monitoring with IUPC might improve both maternal and fetal outcomes by al- also allows ambulation during moni- Reprints: Tal Biron-Shental, MD, Department toring. EUM has been shown to corre- of Obstetrics and Gynecology, Meir Medical lowing better adjustment of oxytocin, thus Center, 59 Tchernichovsky St., Kfar Saba preventing uterine hyperstimulation and spond strongly with tocodynamomet- 44821, Israel. [email protected]. fetal hypoxia, or by enabling better inter- ric sensor in measuring contractions 19,22 0002-9378/$36.00 pretation of abnormal fetal heart rate pat- and predicting preterm labor. © 2012 Mosby, Inc. All rights reserved. terns in relation to uterine activity. This The aim of this study was to compare doi: 10.1016/j.ajog.2011.12.015 hypothesis is mainly based on expert EUM and IUPC monitoring in terms of See Journal Club, page 449 opinion, as limited clinical data are onset, time to peak, duration, frequency, available to support it. A randomized and intensity of uterine contractions. 412.e1 American Journal of Obstetrics & Gynecology MAY 2012 www.AJOG.org Obstetrics Research tions were compared. The data evalua- TABLE tor was blinded to the stage of labor Demographic and clinical characteristics of participants that was recorded, as well as to the out- .Parameter Range Average ؎ SD come of the labor Maternal BMI 20.2–41.6 30.31 Ϯ 4.626 IUPC was measured using millimeters .............................................................................................................................................................................................................................................. of mercury (mm Hg) and EUM, in ␮W. Gravity 1–11 3 Ϯ 2.77 .............................................................................................................................................................................................................................................. Evaluated parameters were the onset Parity 0–8 2 Ϯ 2.26 .............................................................................................................................................................................................................................................. of the contraction, its peak, time to na- Gestation 32 wk ϩ 4 d–42 wk ϩ 6 d 39 wk ϩ 4dϮ 2wkϩ 2d dir, the duration, and intensity of each .............................................................................................................................................................................................................................................. Initial cervical dilatation, cm 1–9.5 4.7 Ϯ 1.9 contraction. As accepted while using .............................................................................................................................................................................................................................................. IUPC, we also calculated the total eleva- Fetal weight, g 1490–4300 3261 Ϯ 584 tion of mm Hg above baseline in all con- .............................................................................................................................................................................................................................................. Mode of delivery No. of parturients Percentage tractions during 10 minutes (known as .............................................................................................................................................................................................................................................. Montevideo units) and the total ␮W Normal vaginal delivery 22 46.8 .............................................................................................................................................................................................................................................. during the 10 minutes measured by the Cesarean section 18 38.3 EUM. The novel software of the tested .............................................................................................................................................................................................................................................. Vacuum-assisted vaginal delivery 7 14.9 device created the waveform of the con- .............................................................................................................................................................................................................................................. tractions and enabled us to calculate the Augmentation of labor with oxytocin 40 .............................................................................................................................................................................................................................................. area under the curve of the contractions BMI, body mass index. that were detected by the new method in Haran. A comparison of intrauterine pressure catheters and electrical activity of the myometrium. Am J Obstet a similar way to the accepted evaluation Gynecol 2012. of Montevideo while using IUPC. We compared the ratios of these measure- MATERIALS AND METHODS difficulties with recording contractions ments in each participant. Since the units This prospective observational study was by the IUPC or after