Progestin treatment for the prevention of preterm birth

Progestin supplementation appears to be a promising approach to both preventing initiation of preterm labor and treating it once it is already established, given the role of progesterone in maintaining pregnancy, as well as support from basic and clinical research. Progesterone and 17α-hydroxyprogesterone acetate slow the process of cervical ripening, and this is the rationale for prophylactic long-term progestin supplementation mostly studied so far. However, progesterone (but not 17α-hydroxyprogesterone acetate) also inhibits myometrial activity even after the cervix has already ripened. Moreover, these effects depend greatly on the vehicle used and the route of administration. Understanding different mechanisms of action, as well as the importance of progestin formulation, vehicle and route of administration, is the key to finding the optimal progestin treatment for prevention of preterm birth.

Use of uterine electromyography to diagnose term and preterm labor

Current methodologies to assess the process of labor, such as tocodynamometry or intrauterine pressure catheters, fetal fibronectin, cervical length measurement and digital cervical examination, have several major drawbacks. They only measure the onset of labor indirectly and do not detect cellular changes characteristic of true labor. Consequently, their predictive values for term or preterm delivery are poor. Uterine contractions are a result of the electrical activity within the myometrium. Measurement of uterine electromyography (EMG) has been shown to detect contractions as accurately as the currently used methods. In addition, changes in cell excitability and coupling required for effective contractions that lead to delivery are reflected in changes of several EMG parameters. Use of uterine EMG can help to identify patients in true labor better than any other method presently employed in the clinic.

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.

Pharmacologic actions of progestins to inhibit cervical ripening and prevent delivery depend on their properties, the route of administration, and the vehicle

OBJECTIVE

The purpose of this study was to evaluate cervical changes and delivery at term during pregnancy in rats after various progestin treatments.

STUDY DESIGN

Pregnant rats were treated by various routes and vehicles with progesterone, 17-alpha-hydroxyprogesterone caproate (17P), R5020, and RU-486. Delivery time was determined and cervical ripening was assessed in vivo by collagen light-induced fluorescence.

RESULTS

The cervix is rigid in the progesterone injection, 17P, and vaginal R5020 groups vs controls. Vaginal progesterone had no effect. RU-486 treatment softened the cervix during preterm delivery. Only subcutaneous injected progesterone, R5020 (subcutaneous and vaginal), and topical progesterone in sesame and fish oil inhibits delivery. Delivery is not changed by subcutaneous injection of 17P, vaginal progesterone, oral progesterone, and topical progesterone in Replens (Crinone; Columbia Labs, Livingston, NJ).

CONCLUSION

Inhibition of cervical ripening and delivery by progestins depends on many factors that include their properties, the route of administration, and the vehicle. This study suggests reasons that the present treatments for preterm labor are not efficacious.

The effect of bilateral pelvic neurectomy on cervical ripening in pregnant rats

AIMS

To determine the effect of bilateral pelvic neurectomy (BPN) on cervical ripening in pregnant rats by measuring cervical extensibility and changes in collagen cross-linkages.

METHODS

Timed-pregnant rats were randomly laparotomized on days 9 or 10 of gestation and the pelvic nerves were exposed and either bilaterally transected, or left intact in sham control animals. The rats were sacrificed on day 18 and the uterine cervices obtained. Cervical ripening was assessed by cervical resistance-to-stretch, light-induced autofluorescence (LIF) of cross-linked collagen, and collagen changes analyzed by picrosirius polarization microscopy.

RESULTS

Measurements of extensibility and collagen cross-linkages indicated that after BPN the cervix was significantly more ripened than the cervix from sham control animals.

CONCLUSION

BPN stimulates cervical ripening instead of inhibiting this event as previously proposed. Further studies in this area could be critical for developing treatments for dystocia, preterm labor, and cervical insufficiency.

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

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.

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.

Challenge with ovalbumin antigen increases uterine and cervical contractile activity in sensitized guinea pigs

OBJECTIVE

The aims of this study were to investigate the effects of ovalbumin challenge on uterine and cervical contractility, intrauterine pressure, and uterine electromyography activity in sensitized guinea pigs.

STUDY DESIGN

Guinea pigs were sensitized by injection of ovalbumin-aluminum hydroxide suspension. Control animals were injected with the aluminum hydroxide suspension only. On days 55-57 of pregnancy, longitudinal uterine and cervical strips from guinea pigs were prepared for isometric tension recording. Nonpregnant guinea pigs were outfitted with telemetric transducers to record intrauterine pressure and uterine electromyography.

RESULTS

Ovalbumin significantly increased contractility of uterine and cervical strips from sensitized versus nonsensitized animals. These effects were abolished by histamine H(1) receptor antagonist in uterine strips and by histamine H(1) receptor antagonist and a mast cell stabilizer in cervical strips from sensitized animals. Cyclooxygenase and 5-lipoxygenase inhibitors had no significant effect on the response to ovalbumin. Treatment with ovalbumin in vivo significantly increased intrauterine pressure and uterine electromyography activity in sensitized but not in nonsensitized, animals.

CONCLUSION

Our findings indicate that type I hypersensitivity reactions may be important in mediating uterine contractility in pregnant and nonpregnant states.

Identification of term and preterm labor in rats using artificial neural networks on uterine electromyography signals

OBJECTIVE

This study was undertaken to use artificial neural networks on uterine electromyography data to identify term and preterm labor in rats.

STUDY DESIGN

Controls (group 1: n = 4) and preterm labor models (group 2: n = 4, treated with onapristone) were used. Uterine electromyography and intrauterine pressure (IUP) variables were measured by implanted telemetric devices. For each timepoint assessed, either a "labor event" or "nonlabor event" was first assigned by using visual and other means. 112 total labor and nonlabor events were observed. Artificial neural networks were then used with electromyography and intrauterine pressure parameters to attempt algorithmic, objective identification for time of labor in each group.

RESULTS

For group 1, all 8 (100%) labor events and all 44 (100%) nonlabor events were correctly identified by the artificial neural networks. For group 2, 22 of 24 (92%) labor events and 31 of 36 (86%) nonlabor events were correctly determined by the artificial neural networks.

CONCLUSION

Artificial neural networks can effectively predict term and preterm labor during pregnancy with the use of uterine electromyography and intrauterine pressure variables.

Characterization of abdominally acquired uterine electrical signals in humans, using a non-linear analytic method

The present work seeks to determine if a particular non-linear analytic method is effective at quantifying uterine electromyography (EMG) data for estimating the onset of labor. Twenty-seven patients were included, and their uterine EMG was recorded non-invasively for 30 min. The patients were grouped into two sets: G1: labor, N = 14; G2: antepartum, N = 13. G1 patients all delivered spontaneously within 24 h of recording while G2 patients did not. The uterine electrical signals were analyzed offline by first isolating the uterine-specific frequency range and then randomly selecting "bursts" of uterine electrical activity (each associated with a uterine contraction) from every recording. Wavelet transform was subsequently applied to each of the bursts' traces, and then the fractal dimension (FD) of the resulting transformed EMG burst-trace was calculated (Benoit 1.3, Trusoft). Average burst FD was found for each patient. FD means for G1 and G2 were calculated and compared using t test. FD was significantly higher (P < 0.05) for G1: 1.27 +/- 0.03 versus G2: 1.25 +/- 0.02. The wavelet-decomposition-generated fractal dimension can be used to successfully discern between patients who will deliver spontaneously within 24 h and those who will not, and can be useful for the objective classification of antepartum versus labor patients.

Physiology and electrical activity of uterine contractions

Presently, there is no effective treatment for preterm labor. The most obvious reason for this anomaly is that there is no objective manner to evaluate the progression of pregnancy through steps leading to labor, either at term or preterm. Several techniques have been adopted to monitor labor, and/or to diagnose labor, but they are either subjective or indirect, and they do not provide an accurate prediction of when labor will occur. With no method to determine preterm labor, treatment might never improve. Uterine electromyography (EMG) methods may provide such needed diagnostics.

Diabetes induces sex-dependent changes in neuronal nitric oxide synthase dimerization and function in the rat gastric antrum

Diabetic gastroparesis is a disorder that predominantly affects women. However, the biological basis of this sex bias remains completely unknown. In this study we tested the hypothesis that a component of this effect may be mediated by the nitrergic inhibitory system of the enteric nervous system. Age-matched male and female Sprague-Dawley rats were studied 8 or 12 wk after streptozotocin (55 mg/kg body wt ip)-induced sustained hyperglycemia and compared with controls. Solid gastric emptying (GE) studies were performed in all the groups. Changes in gastric antrum neuronal nitric oxide synthase (nNOS) mRNA and protein levels were analyzed by real-time PCR and Western immunoblotting, respectively. nNOS dimerization studies were performed using low-temperature SDS-PAGE. In vitro nitrergic relaxation (area under curve/mg tissue wt) was studied after the application of electric field stimulation in an organ bath. Changes in intragastric pressure (mmHg.s) in freely moving rats in the presence or absence of N(G)-nitro-l-arginine methyl ester (nitric oxide synthase inhibitor) were examined by an ambulatory telemetric method. After diabetes induction, GE is delayed in both male and female rats. However, diabetic females exhibited significant delayed GE than in diabetic males. Compared with male controls, gastric nNOS expression and nitrergic relaxation were substantially elevated in healthy female control rats, accompanied by significantly reduced intragastric pressure. The active dimeric form and dimer-to-monomer ratio of nNOSalpha were also higher in healthy females compared with male rats (P < 0.05). Diabetic females, but not males, showed significant (P < 0.05) impairment in both gastric nNOSalpha dimerization and nitrergic relaxation, accompanied by an increase in intragastric pressure. Our data provide evidence that females may have a greater dependency on the nitrergic mechanisms in health. Furthermore, diabetes seems to affect the nitrergic system to a greater extent in females than in males. Together, these changes may account for the greater vulnerability of females to diabetic gastric dysfunction.

Identification of human term and preterm labor using artificial neural networks on uterine electromyography data

OBJECTIVE

To use artificial neural networks (ANNs) on uterine electromyography (EMG) data to classify term/preterm labor/non-labor pregnant patients.

MATERIALS AND METHODS

A total of 134 term and 51 preterm women (all ultimately delivered spontaneously) were included. Uterine EMG was measured trans-abdominally using surface electrodes. "Bursts" of elevated uterine EMG, corresponding to uterine contractions, were quantified by finding the means and/or standard deviations of the power spectrum (PS) peak frequency, burst duration, number of bursts per unit time, and total burst activity. Measurement-to-delivery (MTD) time was noted for each patient. Term and preterm patient groups were sub-divided, resulting in the following categories: [term-laboring (TL): n = 75; preterm-laboring (PTL): n = 13] and [term-non-laboring (TN): n = 59; preterm-non-laboring (PTN): n = 38], with labor assessed using clinical determinations. ANN was then used on the calculated uterine EMG data to algorithmically and objectively classify patients into labor and non-labor. The percent of correctly categorized patients was found. Comparison between ANN-sorted groups was then performed using Student's t test (with p < 0.05 significant).

RESULTS

In total, 59/75 (79%) of TL patients, 12/13 (92%) of PTL patients, 51/59 (86%) of TN patients, and 27/38 (71%) of PTN patients were correctly classified.

CONCLUSION

ANNs, used with uterine EMG data, can effectively classify term/preterm labor/non-labor patients.

Comparing uterine electromyography activity of antepartum patients versus term labor patients

OBJECTIVE

The purpose of this study was to compare uterine electromyography of patients delivering>24 hours from measurement with laboring patients<or=24 hours from measurement.

STUDY DESIGN

Fifty patients (group 1: labor, n=24; group 2: antepartum, n=26) were monitored using transabdominal electrodes. Group 2 was recorded at several gestations. Uterine electrical "bursts" were analyzed by power-spectrum from 0.34 to 1.00 Hz. Average power density spectrum (PDS) peak frequency for each patient was plotted against gestational age, and compared between group 1 and group 2. Frequency was partitioned into 6 bins, and associated burst histograms compared.

RESULTS

Group 1 was significantly higher than group 2 for gestational age (39.87+/-1.08 vs 32.96+/-4.26 weeks) and average PDS peak frequency (0.51+/-0.10 vs 0.40+/-.03 Hz). Histograms were significantly different. A correlation coefficient of .41, with significance, was found with PDS vs gestation.

CONCLUSION

Uterine electromyography in antepartum patients is significantly lower than in laboring patients delivering<or=24 hours from measurement.

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.

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.

DESIGN

Review of recent studies.

SETTING

University of Texas Medical Branch Labour and Delivery Clinics.

POPULATION

Various groups of pregnant women.

METHODS

We have developed and recently improved non-invasive methods to evaluate quantitatively uterine electrical signals from the abdominal surface and cervical collagen.

MAIN OUTCOME MEASURES

Uterine EMG utilised power density spectrum (PDS) peak frequency and total power (P(0)) and cervical LIF utilising LIF ratio.

RESULTS

Human studies indicate that uterine and cervical performance can be successfully monitored during pregnancy using EMG and LIF, respectively, and the assessment of uterine and cervical function can both be used to influence patient management in a variety of conditions associated with labour, more than can currently available methods.

CONCLUSIONS

The potential benefits of the proposed instrumentation include the following: a reduction in the rate of preterm birth, improved maternal and perinatal outcome, better monitoring of treatment, decreased caesarean section rate and better research methods for understanding uterine and cervical function.

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.

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 spectrum's 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.