William L. Maner

Predicting Term and Preterm Delivery With Transabdominal Uterine Electromyography

OBJECTIVE To determine whether delivery can be predicted using transabdominal uterine electromyography. METHODS A total of 99 patients were grouped as either term (37 weeks or more) or preterm (less than 37 weeks). Uterine electrical activity was recorded for 30 minutes in clinic. Electromyographic “bursts” were evaluated to determine the power density spectrum. Measurement-to-delivery time was compared with the average power density spectrums peak frequency. Receiver operating characteristic curve analysis was performed for 48, 24, 12, and 8 hours from term delivery, and 6, 4, 2, and 1 day(s) from preterm delivery. RESULTS The power density spectrum peak frequency increased as the measurement-to-delivery interval decreased. Receiver operating characteristic curve analysis gave high positive and negative predictive values for both term and preterm delivery. At term, the average power density spectrum peak frequency was significantly higher for the 24-or-fewer-hours-to-delivery group than for the more-than-24-hours-to-delivery group, whereas at preterm, the average power density spectrum peak frequency was significantly higher in the 4-or-fewer-days-to-delivery group than in the more-than-4-days-to-delivery group (P < .05). CONCLUSION Transabdominal uterine electromyography predicts delivery within 24 hours at term and within 4 days preterm. This methodology offers many advantages and benefits that are not available with present uterine monitoring systems.

Non-invasive transabdominal uterine electromyography correlates with the strength of intrauterine pressure and is predictive of labor and delivery.

Objective: The study was conducted to investigate whether the strength of uterine contractions monitored invasively by intrauterine pressure catheter could be determined from transabdominal electromyography (EMG) and to estimate whether EMG is a better predictor of true labor compared to tocodynamometry (TOCO). Study design: Uterine EMG was recorded from the abdominal surface in laboring patients simultaneously monitored with an intrauterine pressure catheter (n = 13) or TOCO (n = 24). Three to five contractions per patient and corresponding electrical bursts were randomly selected and analyzed (integral of intrauterine pressure; integral, frequency, amplitude of contraction curve on TOCO; burst energy for EMG). The Mann–Whitney test, Spearman correlation and receiver operator characteristics (ROC) analysis were used as appropriate (significance was assumed at a value of p < 0.05). Results: EMG correlated strongly with intrauterine pressure (r = 0.764; p = 0.002). EMG burst energy levels were significantly higher in patients who delivered within 48 h compared to those who delivered later (median [25%/75%]: 96 640 [26 520–322 240] vs. 2960 [1560–10 240]; p < 0.001), whereas none of the TOCO parameters were different. In addition, burst energy levels were highly predictive of delivery within 48 h (AUC = 0.9531; p < 0.0001). Conclusion: EMG measurements correlated strongly with the strength of contractions and therefore may be a valuable alternative to invasive measurement of intrauterine pressure. Unlike TOCO, transabdominal uterine EMG can be used reliably to predict labor and delivery.

Methods and Devices for the Management of Term and Preterm Labor

In this review, we outline studies showing that the uterus (myometrium) and cervix pass through a conditioning step in preparation for labor. This step is not easily identifiable with present methods designed to assess the uterus or cervix. In the uterus, this seemingly irreversible step consists of changes in the electrical properties that make muscle more excitable and responsive and produce forceful contractions. In the cervix, the step consists of softening of the connective tissue components. Progesterone and nitric oxide appear to have important roles in these processes. The progress of labor can be assessed noninvasively using electromyographic (EMG) signals from the uterus (the driving force for contractility) recorded from the abdominal surface. Uterine EMG bursts detected in this manner characterize uterine contractile events during human and animal pregnancy. A low uterine EMG activity, measured transabdominally throughout most of pregnancy, rises dramatically during labor. EMG activity also increases substantially during preterm labor in humans and rats and may be predictive of preterm labor. A quantitative method for assessing the cervix is also described. A collascope estimates cervical collagen content from a fluorescent signal generated when collagen crosslinks are illuminated with an excitation light of about 340 nm. The system has proved useful in rats and humans at various stages of pregnancy and indicates that cervical softening occurs progressively in the last one‐third of pregnancy. In rats, collascope readings correlate with resistance measurements made in the isolated cervix, which may help to assess cervical function during pregnancy and indicate controls and treatments.

Uterine Electromyography and Light-Induced Fluorescence in the Management of Term and Preterm Labor

Objective: Understanding the physiology of the uterus and cervix during term and preterm parturition is crucial for developing methods to control their function and is essential to solving clinical problems related to labor. To date, only crude, inaccurate, and subjective methods are used to assess changes in uterine and cervical function in pregnancy. Methods: In the past several years, we have developed noninvasive methods to quantitatively evaluate the uterus and cervix based on recording of uterine electrical signals from the abdominal surface (uterine electromyography) and measurement of light-induced fluorescence (LIF) of cervical collagen (Collascope), respectively. Both methods are rapid and allow immediate assessment of uterine contractility and cervical ripening. Results: Studies in animals and humans indicated that uterine and cervical performance can be monitored successfully during pregnancy using those approaches and that these techniques can be used during labor to better define management in a variety of conditions associated with labor. Conclusions: The potential benefits of the proposed instrumentation and methods include reducing the rate of preterm delivery, improving maternal and perinatal outcome, monitoring treatment, decreasing cesarean rate and providing research methods to understand uterine and cervical function.

Cervical ripening and insufficiency: from biochemical and molecular studies to in vivo clinical examination.

To understand cervical ripening and especially the pathophysiology of cervical insufficiency, it is important to know the cervical composition: the cervix is dominated by fibrous connective tissue, consisting predominantly of Type I collagen (70%). Despite many studies of the cervix, we still rely upon relatively crude methods for clinical evaluation of the cervix. If the amount of cervical collagen plays a role in cervical insufficiency and in success of or length of induction of labor, then measurements of cervical collagen may provide an objective means of establishing the diagnosis or prognosis. We have established and reported a non-invasive means, called Collascope, to measure collagen cross-linking using light-induced fluorescence (LIF), and which is specifically designed to assess cervical ripening, and functions by measuring the natural fluorescence of non-soluble collagen in the cervix. Studies conducted in animals and humans in a variety of settings indicate that cervical function can be successfully monitored using the Collascope during pregnancy: LIF correlates negatively with gestational age and positively with time-to-delivery interval, and is predictive of delivery within 24h. Additionally LIF is significantly lower in women with cervical insufficiency. We suggest that the Collascope might be useful to better define management in cases of spontaneous preterm or induced term cervical ripening. From our studies and others, it is clear that in forecasting (pre-)term cervical ripening, the capability of the technologies and bioassays that have been generally accepted into clinical practice are limited. Any devices shown to be superior to the clinically accepted tests currently used should be quite useful for clinicians. The Collascope offers an objective measurement of both the function and state of the cervix, by directly measuring collagen cross-linking using LIF.

Use of uterine EMG and cervical LIF in monitoring pregnant patients

Objectives  Review the uterine electromyography (EMG) and cervical light‐induced fluorescence (LIF) devices and their role in the evaluation of uterine and cervical function in comparison with present methods.

Uterine electromyography characteristics for early diagnosis of mifepristone-induced preterm labor

OBJECTIVE: Differentiating uterine contractions leading to preterm birth from ineffective uterine activity is difficult with current tools. Uterine electromyographic activity is recordable and consists of bursts (group of action potentials) characterized by characteristics that are different during pregnancy and labor. Our aim was to identify the chronology of the changes in uterine pressure and electromyographic characteristics during mifepristone-induced preterm labor in pregnant rats and to determine the earliest characteristic to change. METHODS: On day 17 of gestation, intrauterine catheter and electromyography electrodes were implanted in the uterus. On day 18, rats were allocated for treatment with mifepristone or placebo. Intrauterine pressure and electromyography integral activities and electromyography mean were calculated before treatment and 6, 12, 18, 20, 22, and 24 hours after treatment. After mathematical transformation, burst analysis was performed by using power density spectrum energy, peak amplitude, and frequency. RESULTS: As expected, delivery rate within 24 hours was higher in the mifepristone-treated group. Changes in electromyography integral activity and mean, power density spectrum energy, and intrauterine pressure integral activity occurred late during preterm labor, in a range of 2–4 hours before delivery. Electromyography peak frequency of the power density spectrum exhibited early changes, with a shift from low to high frequencies starting at 12 hours before delivery. CONCLUSION: Electromyography peak frequency of the power density spectrum from individual bursts was the first characteristic to change after antiprogestin treatment, preceding any change in intrauterine pressure, making it a potentially useful marker for the early diagnosis of preterm labor.

The physiology of uterine contractions

Studies in animals and humans indicate that uterine performance can be successfully monitored during pregnancy using uterine electromyography. Uterine electromyography could be used to better define management in a variety of conditions associated with human labor. The potential benefits of the proposed instrumentation and method include: reducing the rate of preterm delivery, improving maternal and perinatal outcome, monitoring treatment, decreasing cesarean-section rate, and providing research methods to better understand uterine function.

The effect of bilateral pelvic neurectomy on uterine and abdominal electrical and pressure activity, as measured by telemetry in conscious, unrestrained pregnant rats.

Abstract Aims: Bilateral pelvic neurectomy (BPN) interferes with delivery in rats. This work measures the effect of BPN on uterine and abdominal electromyography (EMG) and pressure during gestation and delivery. Methods: Uterine EMG and intra-uterine pressure (IUP), as well as abdominal muscle EMG and intra-abdominal pressure (IAP), were recorded on days 19–24 in rats. Mean values were determined for the peak frequency of the power density spectrum (PDS) of the uterine and abdominal EMG “bursts,” the integral of the abdominal EMG power spectrum (IPS), and the area under the IUP and IAP curves (AUIUP and AUIAP). Results: Uterine EMG power density spectrum peak frequency and AUIUP were low during days 19–21 in all rats, and on days 22–23 increased sharply and significantly in both groups. Before delivery, sham rat recordings showed sudden sharp increases in AUIAP, AUIUP and IPS as “pushing” was observed. Pushing was not observed or recorded in laboring BPN rats and they did not deliver normally. Conclusions: A functional pelvic nerve is required for normal labor and delivery in rats. BPN inhibits abdominal EMG and contractions necessary to expel the fetus.

Inhibitory effects of electrical stimulation on delivery in pregnant rats.

OBJECTIVE To study the efficacy of uterine electrical stimulation (ES) with various parameters in delaying delivery in term- and preterm-laboring animals. STUDY DESIGN Catheters and electrodes, as well as ES electrodes, were sutured onto the uterine horn in day-15 pregnant rats. ES with various durations/frequencies (five sets of parameters) was tested from gestation day 21 to determine its effects on uterine contractility. The best set of ES parameters was applied in term (day 21) and preterm (day 18-labor induced) animals to determine the effects of ES on delivery. RESULTS (1) Significant reduction in uterine contractions (0.54+/-0.11 vs. 0.86+/-0.08 contractions per minute, P<0.001) was noted with ES of only one of the five sets of parameters (set #5 with pulse train of 10s on and 10s off, 28ms pulse width, frequency of 30Hz and amplitude of 4mA); (2) ES with parameter set 5 delayed delivery by 12.5h (P=0.01) and reduced area under the curve of intrauterine pressure in mmHgs (311+/-147.21 vs. 848.75+/-350.38, P<0.05) and AUC-electromyographic activity is area under rectified (i.e. absolute value) uterine EMG trace in mVs (145.25+/-93.1 vs. 410+/-182.46, P<0.05) in the term rats; and (3) similar effects were noted with ES in preterm rats with a delay in delivery by 28h (P<0.001), and a decrease in IUP-AUC (intrauterine pressure-area under curve) (101.5+/-55.45 vs. 551+/-269.06, P=0.017) and EMG-AUC (64.25+/-43.63 vs. 172.5+/-62.91, P=0.03). CONCLUSION ES of the uterus with appropriate parameters inhibits uterine contractions and delays delivery in both term and preterm rats.