Review Matrix for Extant Literature on Contraction Activity Measures and Labor Dystocia

Primary Author	Study Description	Results
Althaus et al18	Purpose to evaluate the association between F:R and cephalopelvic disproportion.	Increased F:R was associated with cesarean for labor arrest (F:R, 1.55; SD, 0.28; 95% CI, 0.91–2.30 for vaginal birth vs 1.77; SD, 0.40; 95% CI, 1.0–2.46 for cesarean; P = .00003).
	Retrospective, case-control study of nulliparous women with a single, term fetus in the vertex position in the United States (n = 200, 100 with cephalopelvic disproportion and 100 without).
		In women who received oxytocin. augmentation, increased F:R was associated with cesarean (F:R, 1.52 for vaginal birth vs 1.63 for cesarean; P = .0225).
	Uterine contractions monitored for 1 h by external TOCO or intrauterine pressure at ≥4 cm dilatation.
	F:R calculated for each contraction and averaged over one hr.
Ebrahimzadeh et al16	Purpose to assess the correlation between self-reported maternal fatigue and F:R.	Increased F:R was associated with fatigue severity (r = 0.27; P = .007).
	Cross-sectional study in Iran (n = 100 nulliparous women).	Length of first stage of labor was also associated with fatigue severity although less strongly.
	F:R of each contraction measured by TOCO averaged over 30 min.
		Contraction frequency was not significantly associated with fatigue severity.
	Self-report fatigue was assessed at 3–4 cm dilation using a visual analog scale anchored with “no fatigue at all” to “the most fatigue I’ve ever had.”
Ebrahimzadeh Zagami et al17	Purpose to evaluate the relationship between F:R and cesarean for labor dystocia.	Increased mean F:R was associated with cesarean (F:R 1.13, SD 0.193 for vaginal birth vs 1.64, SD 0.30 seconds for cesarean, P < .001).
	Cross-sectional prospective study of nulliparous women in spontaneous labor with a term, singleton, vertex fetus in Iran (n = 200, 162 with vaginal birth and 38 with cesarean).
		Decreased frequency of contractions was associated with cesarean (F:R, 8.3; SD, 2.3 for vaginal birth vs 7.05; SD, 1.46 for cesarean; t = 3.192; P = .002).
	F:R measured by TOCO measured at 3–5 cm dilation and averaged over 30 min.
	Frequency of contractions was measured as the number of contractions in 30 min.	Newborn weight, height and head circumference were all significantly higher in the cesarean group (P < .001, P = .001, P = .003, respectively).
Euliano et al10	Purpose to compare spatiotemporal patterns of uterine electrical activity in normal and arrested labors.	All participants sustained contraction frequency of every 1–3mins and of the 11 women with cesarean, all achieved MVUs >150 mm Hg.
	Case-control study using data derived from a previous study of women in spontaneous labor in the United States (n = 36, 12 women with cesarean for active-phase arrest matched to 24 women in a control group with vaginal birth).
		Predominately upward fundal movement was more common in those with vaginal birth (23/24 with vaginal birth vs 4/12 cesarean, P = .003).
	Using a 30-min uterine EMG segment during arrest or at the same dilation in women in the control group, the center of uterine electrical activity was identified, and the vertical motion of the center determined for each contraction.	ROC analysis of logistic regression model including gestational age, BMI, parity, spontaneous vs induced labor and dilation at time of measurement gave an AUC of 0.91 for predicting outcome based on the different patterns of movement.
Edwards et al19	Purpose to evaluate the relationship between fundal dominance of uterine electrohysterography and cesarean birth for labor dystocia.	Fundal-dominant contractions were not associated with cesarean for labor dystocia (88.7% ± 10.2 with cesarean for labor dystocia vs 86.0% ± 11.4, P = 0.44).
	Prospective cohort study of nulliparous women at term in spontaneous labor (n = 167, 11 with cesarean for labor dystocia, n = 156 all others).
Moghaddam et al15	Purpose to find a correlation between F:R and cesarean for failure to progress or cephalopelvic disproportion.	Increased F:R was associated with cesarean (F:R, 1.54; SD, 0.26 for vaginal birth vs 1.74; SD, 0.21 for cesarean; OR = 0.44; 95% CI, 0.005–0.42; P < .001).
	Prospective cohort study of women in labor in Iran (n = 120, 60 with vaginal birth and 60 with cesarean for failure to progress or cephalopelvic disproportion).
		Sensitivity = 68.32%, Specificity = 70.01%, Positive predictive value = 69.55%, negative predictive value = 68.91%.
	F:R measured by TOCO at 4–7 cm dilation, without oxytocin augmentation, for each contraction and averaged over 1 h.	ROC analysis AUC .75 with a cutoff point of 1.68.
		Increased F:R associated with maternal age (r = 0.19, P < .001).
Mol et al20	Purpose to provide insight in the lack of a positive effect of IUPC vs TOCO by evaluating the MVU in correlation with dysfunctional labor and adverse neonatal outcome.	Only 47% of women with vaginal birth reached MVU >200.
		Risk of cesarean was higher in women who had lower MVUs during labor (likelihood ratio 1.6; 95% CI, 0.98–2.5 for MVU <100 vs 0.41; 95% CI, 0.18–0.68 for MVU >300).
	Secondary analysis of a randomized controlled trial of women with IUPC monitoring in the Netherlands (n = 503, 403 with vaginal birth and 100 with cesarean).
		MVUs were not associated with adverse neonatal outcomes.
	Highest MVU measured at any time in labor categorized as <100, 100–199, 200–299, or ≥300.	Lower MVUs were associated with older women, longer gestational age, longer labors, and higher birth weight.
	MVUs were also measured at last vaginal examination during the first stage of labor and categorized as <200 or >200.
Oppenheimer et al14	Purpose to evaluate the relationship of the slopes of contraction frequency and SD of contraction frequency over the course of labor with augmentation and cesarean.	The interpeak interval decreased over the course of normal labor and the slope was steeper than in women with labor dystocia and/or cesarean (mean slope of interpeak frequency, −47.15 with vaginal birth and no augmentation; mean slope of interpeak frequency, −6.15 with cesarean following augmentation, P = .0004).
	Case-control study of women in labor in Canada (n = 192, 64 with cesarean matched with 128 with vaginal birth).
	TOCO reviewed retrospectively in successive 30-min periods between 3 and 8 cm dilation
		SD of interpeak interval followed a similar pattern as the interpeak interval (mean slope of SD, −0.76 with vaginal birth and no augmentation; mean slope of SD, +0.4, with cesarean following augmentation)
	Frequency was calculated as the average of 5 consecutive interpeak intervals.
	SD of 5 consecutive interpeak intervals was recorded.
Vasak et al13	Purpose to evaluate whether uterine EMG identifies inefficient contractions leading to arrest of labor and cesarean.	Mean power density spectrum peak frequency was higher in women with cesarean for first-stage labor arrest following augmentation than in women giving birth vaginally without augmentation or with augmentation (P = .001 and .01, respectively).
	Cohort study of n = 119 nulliparous women with a term, singleton, vertex fetus in spontaneous labor in the Netherlands (n = 119, 32 with vaginal birth without augmentation, 73 with vaginal birth following augmentation, 14 with cesarean following augmentation).
		In women who gave birth vaginally with augmentation, mean power density spectrum peak frequency was higher after augmentation (P = .001).
	Uterine EMG power density spectrum peak frequency was calculated and averaged throughout admission.
Vrhovec et al12	Purpose to evaluate the relationship between EMG sample entropy and labor progress.	In normally progressing labor, sample entropy decreased from median 0.15 (range, 0.13–0.25) at 3 cm dilation to median 0.09 (range, 0.08–0.11) at birth measured on the abdominal surface and from median 0.12 (range, 0.08–0.13) at 3 cm to median 0.03 (range, 0.03–0.05) measured from the uterine corpus. With labor dystocia, only the cervix EMG was reported. Sample entropy decreased during periods of normal progression and increased during dystocia. Median sample entropy was 0.14 (range, 0.08–0.15) at 3 cm, median 0.05 (range, 0.02–0.13) prior to the delay, median 0.22 (range, 0.18–0.25) during the delay, and median 0.04 (range, 0.02–0.05) when normal progress resumed.
	Cohort study of nulliparous women with a term, singleton, vertex fetus in induced labor in Slovenia (n = 28).
	EMG was collected throughout hospital admission using an electrode array consisting of 12 bipolar electrodes on the abdominal surface and cervix.
	Sample entropy was calculated in contraction bursts and successive nonoverlapping segments.
	Labor progress, based on fetal head station was graphed on the partogram, and classified as delayed when station maintained the same value for 2 hr or more.
Vrhovec11	Purpose to evaluate feasibility of measuring labor dystocia with sample entropy calculated from uterine EMG.	In women with normal labor (n = 13), sample entropy decreased throughout labor to birth.
	Prospective cohort study of nulliparous women with a term, singleton, vertex fetus in labor in Slovenia (n = 32, 13 with normal labor, 4 with delayed labor, 15 with augmented labor).	In delayed labors (n = 4), sample entropy increased during the delay and then continued to decrease.
		In augmented labor (n = 15), sample entropy increased during slow labor progress, decreased through periods of oxytocin augmentation, and increased with every additional slowing in labor progress, prior to increasing the dose of oxytocin.
	Contractions were measured throughout admission for labor by EMG using 12 bipolar electrodes on the abdominal surface and/or a cervical probe.
	Sample entropy was calculated in successive nonoverlapping segments and graphed over time along with cervical dilation and head station.

Abbreviations: AUC, area under the curve; BMI, body mass index; EMG, electromyography; F:R, fall-to-rise ratio; IUPC, intrauterine pressure catheter; MVU, Montevideo unit; OR, odds ratio; ROC, receiver operator characteristic curve; TOCO, tocodynamometry.