Insufficient remodelling of the uterine connective tissue in women with protracted labour

Tafoxiparin, a novel drug candidate for cervical ripening and labor augmentation: results from 2 randomized, placebo-controlled studies

BACKGROUND

Slow progression of labor is a common obstetrical problem with multiple associated complications. Tafoxiparin is a depolymerized form of heparin with a molecular structure that eliminates the anticoagulant effects of heparin. We report on 2 phase II clinical studies of tafoxiparin in primiparas. Study 1 was an exploratory, first-in-pregnant-women study and study 2 was a dose-finding study.

OBJECTIVE

Study 1 was performed to explore the effects on labor time of subcutaneous administration of tafoxiparin before onset of labor. Study 2 was performed to test the hypothesis that intravenous treatment with tafoxiparin reduces the risk for prolonged labor after spontaneous labor onset in situations requiring oxytocin stimulation because of dystocia.

STUDY DESIGN

Both studies were randomized, double-blind, and placebo-controlled. Participants were healthy, nulliparous females aged 18 to 45 years with a normal singleton pregnancy and gestational age confirmed by ultrasound. The primary endpoints were time from onset of established labor (cervical dilation of 4 cm) until delivery (study 1) and time from start of study treatment infusion until delivery (study 2). In study 1, patients at 38 to 40 weeks of gestation received 60 mg tafoxiparin or placebo daily as 0.4 mL subcutaneous injections until labor onset (maximum 28 days). In study 2, patients experiencing slow progression of labor, a prolonged latent phase, or labor arrest received a placebo or 1 of 3 short-term tafoxiparin regimens (initial bolus 7, 21, or 35 mg followed by continuous infusion at 5, 15, or 25 mg/hour until delivery; maximum duration, 36 hours) in conjunction with oxytocin.

RESULTS

The number of participants randomized in study 1 was 263, and 361 were randomized in study 2. There were no statistically significant differences in the primary endpoints between those receiving tafoxiparin and those receiving the placebo in both studies. However, in study 1, the risk for having a labor time exceeding 12 hours was significantly reduced by tafoxiparin (tafoxiparin 6/114 [5%] vs placebo 18/101 [18%]; P=.0045). Post hoc analyses showed that women who underwent labor induction had a median (range) labor time of 4.44 (1.2-8.5) hours with tafoxiparin and 7.03 (1.5-14.3) hours with the placebo (P=.0041) and that co-administration of tafoxiparin potentiates the effect of oxytocin and facilitates a shorter labor time among women with a labor time exceeding 6 to 8 hours (P=.016). Among women induced into labor, tafoxiparin had a positive effect on cervical ripening in 11 of 13 cases (85%) compared with 3 of 13 participants (23%) who received the placebo (P=.004). For women requiring oxytocin because of slow progression of labor, the corresponding results were 34 of 51 participants (66%) vs 16 of 40 participants (40%) (P=.004). In study 2, tafoxiparin had no positive effects on the secondary endpoints when compared with the placebo. Except for injection-site reactions in study 1, adverse events were no more common for tafoxiparin than for the placebo among either mothers or infants. There were few serious or treatment-related adverse events.

CONCLUSION

Subcutaneous treatment with tafoxiparin before labor onset (study 1) may be effective in reducing the labor time among women undergoing labor induction and among those requiring oxytocin for slow progression of labor. Moreover, tafoxiparin may have a positive effect on cervical ripening. Short-term, intravenous treatment with tafoxiparin as an adjunct to oxytocin in patients with labor arrest (study 2) did not affect labor time or other endpoints. Both studies suggest that tafoxiparin has a favorable safety profile in mothers and their infants.

The latent phase of labor

The latent phase of labor extends from the initiation of labor to the onset of the active phase. Because neither margin is always precisely identifiable, the duration of the latent phase often can only be estimated. During this phase, the cervix undergoes a process of rapid remodeling, which may have begun gradually weeks before. As a consequence of extensive changes in its collagen and ground substance, the cervix softens, becomes thinner and dramatically more compliant, and may dilate modestly. All of these changes prepare the cervix for the more rapid dilatation that will occur during the active phase to follow. For the clinician, it is important to recognize that the latent phase may normally extend for many hours. The normal limit for the duration of the latent phase should be considered to be approximately 20 hours in a nullipara and 14 hours in a multipara. Factors that have been associated with a prolonged latent phase include deficient prelabor or intrapartum cervical remodeling, excessive maternal analgesia or anesthesia, maternal obesity, and chorioamnionitis. Approximately 10% of women with a prolonged latent phase are actually in false labor, and their contractions eventually abate spontaneously. The management of a prolonged latent phase involves either augmenting uterine activity with oxytocin or providing a sedative-induced period of maternal rest. Both are equally effective in advancing the labor to active phase dilatation. A very long latent phase may be a harbinger of other labor dysfunctions.

Requirement for oxytocin augmentation in spontaneous parturition is associated with the maternal serum steroid hormones assessed by liquid chromatography coupled to the tandem mass spectrometry

AIM

The aim of research was to evaluate the maternal serum concentration of selected endogenous steroid hormones during spontaneous parturition at term and to determinate their association with the need for oxytocin augmentation.

METHODS

Blood of 108 healthy pregnant women whose parturition started with the regular spontaneous uterine contractions was drawn at the beginning of the labor. Liquid chromatography coupled to the tandem mass spectrometry device was utilized for measurement of sex hormone binding globulin, aldosterone, androstenedione, cortisol, cortisone, corticosterone, dehydroepiandrosterone, dehydroepiandrosteron sulphate, 17-hydroxyprogesterone, progesterone, and testosterone. Mann-Whitney U test, chi-square test, univariate and multivariate logistic regression, and receiver operating characteristic (ROC) analysis were used for the data analysis.

RESULTS

Reference ranges of the selected hormones assessed by liquid chromatography coupled to the tandem mass spectrometry in maternal serum were established. Statistically significant differences in the serum concentration of corticosterone, dehydroepiandrosterone, and androstenedione between mothers requiring oxytocin augmentation and the rest of women having spontaneous parturition were found (p = 0.002, p = 0.008, and p = 0.04, respectively). Concentrations were lower in the group of mothers who required oxytocin infusion for progression of labor. ROC analysis showed that all the mothers with dehydroepiandrosterone serum concentration above 21.6 nmol/L have lower chance to use oxytocin infusion for the labor progression ( area under the curve (AUC)  = 0.649, sensitivity = 71.7%, specificity = 59.6%, p = 0.006).

CONCLUSION

This research provided reference ranges for the selected maternal serum steroid hormones at the beginning of parturition. Association of corticosterone, dehydroepiandrosterone, and androstenedione with the need for the oxytocin infusion usage has been established. Dehydroepiandrosterone could be potential predictor of oxytocin infusion augmentation for progression of the parturition.

Shear wave dispersion as a potential biomarker for cervical remodeling during pregnancy: evidence from a non-human primate model

Shear wave dispersion (variation of phase velocity with frequency) occurs in tissues with layered and anisotropic microstructure and viscous components, such as the uterine cervix. This phenomenon, mostly overlooked in previous applications of cervical Shear Wave Elasticity Imaging (SWEI) for preterm birth risk assessment, is expected to change drastically during pregnancy due to cervical remodeling. Here we demonstrate the potential of SWEI-based descriptors of dispersion as potential biomarkers for cervical remodeling during pregnancy. First, we performed a simulation-based pre-selection of two SWEI-based dispersion descriptors: the ratio R of group velocities computed with particle-velocity and particle-displacement, and the slope S of the phase velocity vs. frequency. The pre-selection consisted of comparing the contrast-to-noise ratio (CNR) of dispersion descriptors in materials with different degrees of dispersion with respect to a low-dispersive medium. Shear waves induced in these media by SWEI were simulated with a finite-element model of Zener viscoelastic solids. The pre-selection also considered two denoising strategies to improve CNR: a low-pass filter with automatic frequency cutoff determination, and singular value decomposition of shear wave displacements. After pre-selection, the descriptor-denoising combination that produced the largest CNR was applied to SWEI cervix data from 18 pregnant Rhesus macaques acquired at weeks 10 (mid-pregnancy stage) and 23 (late pregnancy stage) of the 24.5-week full pregnancy. A maximum likelihood linear mixed-effects model (LME) was used to evaluate the dependence of the dispersion descriptor on pregnancy stage, maternal age, parity and other experimental factors. The pre-selection study showed that descriptor S combined with singular value decomposition produced a CNR 11.6 times larger than the other descriptor and denoising strategy combinations. In the Non-Human Primates (NHP) study, the LME model showed that descriptor S significantly decreased from mid to late pregnancy (-0.37 ± 0.07 m/s-kHz per week, p <0.00001) with respect to the base value of 15.5 ± 1.9 m/s-kHz. This change was more significant than changes in other SWEI features such as the group velocity previously reported. Also, S varied significantly between the anterior and posterior portions of the cervix (p =0.02) and with maternal age (p =0.008). Given the potential of shear wave dispersion to track cervical remodeling, we will extend its application to ongoing longitudinal human studies.

Cervical collagen is reduced in non-pregnant women with a history of cervical insufficiency and a short cervix

INTRODUCTION

Preterm cervical shortening and cervical insufficiency may be caused by a constitutional weakness of the cervix. The aim of this study was to assess the cervical collagen concentration in non-pregnant women with a history of cervical insufficiency or of a short cervix in the second trimester of pregnancy.

MATERIAL AND METHODS

In this case-control study we included non-pregnant women one year or more after pregnancy: 55 controls with a history of normal delivery; 27 women with a history of cervical insufficiency; and 10 women with a history of a short cervix (<5th percentile) and 10 women with a history of a long cervix (>95th percentile) at gestational weeks 18-20. We obtained biopsies (3 × 3-4 mm) from the ectocervix and determined the collagen concentration by measuring the hydroxyproline concentration.

RESULTS

Women with cervical insufficiency had lower collagen concentrations (63.5 ± 5.1%; mean ± SD) compared with controls (68.2 ± 5.4%; p = 0.0004); area under the ROC curve 0.73 (95% CI 0.62-0.84). A cut-off value at 67.6% collagen resulted in a positive likelihood ratio of 3.2, a sensitivity of 60%, and a specificity of 81%. Also, women with a short cervix in the second trimester had lower collagen concentrations in a non-pregnant state (62.1% ± 4.9%) compared with women with a long cervix (67.8% ± 5.0%; p = 0.02).

CONCLUSIONS

Both cervical insufficiency and a short cervix in the second trimester of pregnancy are associated with low cervical collagen concentrations in a non-pregnant state more than one year after pregnancy.

Stereology of human myometrium in pregnancy: influence of maternal body mass index and age

OBJECTIVE

Knowledge of the stereology of human myometrium in pregnancy is limited. Uterine contractile performance may be altered in association with maternal obesity and advanced maternal age. The aim of this study was to investigate the stereology of human myometrium in pregnancy, and to evaluate a potential influence of maternal body mass index (BMI) and age.

STUDY DESIGN

Biopsies of human myometrium were obtained from 57 women at cesarean section (n = 26, n = 13, n = 18 normal, overweight and obese BMI, respectively), and volume fractions of smooth muscle and extracellular matrix were assessed using stereologic techniques.

RESULTS

The smooth muscle constituted 65.2% ± 8.9% (standard deviation) and the extracellular matrix 32.6% ± 7.7% (standard deviation) (n = 57). There was no correlation observed between maternal BMI, age, or parity with the fractional volumes of either smooth muscle or extracellular matrix.

CONCLUSION

These results outline the stereology of human myometrium in pregnancy. Putative functional differences in contractility, pertaining to obese or older mothers, are not related to smooth muscle content.

Cervical collagen concentration within 15 months after delivery

OBJECTIVE

Cervical collagen concentration decreases during pregnancy. The increased risk of preterm birth after a short interpregnancy interval may be explained by an incomplete remodeling of the cervix. The objective of this study was to describe the changes in cervical collagen concentration over 15 months after delivery.

STUDY DESIGN

The collagen concentrations were determined in cervical biopsy specimens that were obtained from 15 women at 3, 6, 9, 12, and 15 months after delivery.

RESULTS

The mean cervical collagen concentrations were 50%, 59%, 63%, 65%, and 65% of dry weight (SD, 4.2-6.5). This increase was statistically significant until month 9, but not between months 9 and 12.

CONCLUSION

Low collagen concentrations in the uterine cervix may contribute to the association between a short interpregnancy interval and preterm birth.

Prostaglandin treatment is associated with a withdrawal of progesterone and androgen at the receptor level in the uterine cervix

Treatment with prostaglandin(PG)-E2 is clinically efficient for cervical priming. The aim of this study was to evaluate the impact of PG-E2 on the expression of the progesterone (PR), androgen (AR) and glucocorticoid (GR) receptors in human uterine cervix in prolonged pregnancy. The study groups were postterm nulliparous women with unripe cervices undergoing cervical priming with PG-E2 before labor induction. Responders (n = 12) who delivered vaginally were compared with non-responders (n = 10), who underwent cesarean section due to failure to progress to the active phase of labor. Controls (n = 18) with vaginal partus at a normal gestational age served as a reference group. Cervical levels of PR-A and PR- B isoforms, AR and GR, serum levels of their ligands and sex hormone-binding globulin (SHBG) were quantified. The responder group displayed lower total PR-AB and AR protein levels as compared to non-responders, and lower PR-B and AR protein levels as compared to controls. In addition, the PR mRNA level was lower in responders as compared to non-responders. The GR protein level did not differ between the groups. We conclude that successful PG-E2 priming was followed by a progesterone and androgen withdrawal at the receptor level in the uterine cervix.

Relationships between mechanical properties and extracellular matrix constituents of the cervical stroma during pregnancy

In normal pregnancy, the cervix maintains its shape during a period of substantial fetal and uterine growth. Hence, maintenance of biomechanical integrity is an important aspect of cervical function. It is known that cervical mechanical properties arise from extracellular matrix (ECM). The most important constituent of the cervical ECM is fibrillar collagen-it is collagen protein that the cervix derives its "strength" from. Other matrix molecules known to affect the collagen network include water, proteoglycans, hyaluronan, and elastin. The objective of this review is to discuss relationships between biochemical constituents and macroscopic mechanical properties. The individual constituents of the ECM will be discussed, especially in regard to collagen remodeling during pregnancy. In addition, the macroscopic mechanical properties of cervical tissue will be reviewed. An improved understanding of the biochemistry of cervical "strength" will shed light on how the cervix maintains its shape in normal pregnancy and shortens in preterm birth.

Changes in the biochemical constituents and morphologic appearance of the human cervical stroma during pregnancy

OBJECTIVE

The cervix is the lower portion of the uterus. It is composed of fibrous tissue and its mechanical integrity is crucial for maintaining a healthy gestation. During normal pregnancy, the cervical extracellular matrix (ECM) remodels in preparation for labor. The objective of this study was to investigate the biochemical and morphological changes in cervical stroma associated with physiological remodeling during normal pregnancy.

STUDY DESIGN

Using human cervical tissue obtained from pregnant and non-pregnant patients, the ECM was analyzed for its biochemical constituents and histologic morphology. The ECM was assayed for hydration, collagen concentration, collagen solubility, total sulfated glycosaminoglycan concentration, and individual disaccharide concentration. The ECM morphology was visualized using conventional histological techniques (Masson's trichrome stain, polarized light microscopy) as well as second harmonic generation (SHG) imaging.

RESULTS

When comparing pregnant to non-pregnant tissue, significant increases were measured for total sulfated glycosaminoglycans, hyaluronic acid, and collagen solubility. The microscopy studies confirmed that the collagenous network of the cervical stroma was anisotropic and pregnancy was associated with a discernable decrease in collagen organization.

CONCLUSION

Significant changes were seen in the concentration and organization of cervical ECM constituents during normal pregnancy.

Ultrasonographic evaluation of myometrial thickness in twin pregnancies

OBJECTIVE

The objective of the study was to evaluate longitudinally the in vivo changes in myometrial thickness (MT) during gestation in patients carrying twin gestations in relation to pregnancy outcome.

STUDY DESIGN

Serial abdominal ultrasounds were performed prospectively in 92 patients carrying twin gestations through each trimester. Ninety-seven patients pregnant with singletons served as controls. For twins, the primary endpoint was spontaneous delivery at less than 35 weeks' gestational age (GA). The myometrium was defined sonographically as the echohomogeneous layer between the serosa and the decidua and was measured at the anterior, fundal, and lower uterine segment (LUS) walls. The estimated fetal weight, maximum vertical pocket of amniotic fluid, and placental thickness were also assessed ultrasonographically at the same time as the MT and served as estimates for the contribution of each to the uterine volume. In twins, cervical length measurements were performed transvaginally, as clinically indicated. Data analysis included 2-way analysis of variance and linear, nonlinear, and multivariate regression.

RESULTS

A total of 41.3% of twin pregnancies (38 of 92) delivered preterm (< 35 weeks). There were no significant changes in measurements at the anterior and fundal site over time throughout pregnancy and no differences in these sites between twin and singleton gestations. Conversely, in both twins and singletons, there was a significant and gradual thinning of the LUS myometrium during gestation. In the absence of uterine contractions or symptoms of preterm labor, twins that delivered preterm had a significantly thinner LUS at an earlier gestation, compared with twins that delivered at term (P < .001), suggesting that LUS thinning occurred earlier in these cases. There was a significant correlation between cervical length and LUS thinning during gestation in twins that delivered 35 weeks GA or later (r = 0.352; P < .001) but not in those that delivered preterm (< 35 weeks GA; r = 0.125; P = .326).

CONCLUSION

Twin pregnancy is characterized by a significant, selective, and gradual thinning of the LUS during gestation, which does not occur in the anterior and fundal myometrium. Thinning of the LUS occurs earlier in twin pregnancies destined to deliver preterm. These observations suggest that similar to the cervix, the LUS changes dynamically during twin pregnancy and that this too may be assessed through ultrasound imaging.

Biomechanical Properties of the Lower Uterine Segment Above and Below the Reflection of the Urinary Bladder Flap

OBJECTIVE

To test the hypothesis that differences in the matrix arrangement of the lower uterine segment (above and below the reflection of the bladder flap) translate to differences in biomechanical or structural properties of the uterine wall.

METHODS

We enrolled prospectively 40 women at term randomized to a bladder flap (n=21) versus no bladder flap (n=19) at the time of a cesarean delivery for dystocia. Tensile properties of tissue biopsies from the upper and lower edges of the hysterotomy incision were quantitated using a stretching regimen designed to mimic labor. Parameters such as slope, yield point, and break point were analyzed in relationship to biochemical (total collagen, sulfated glycosaminoglycans, pyridinoline-deoxypyridinoline) and histological (collagen birefringence) properties of the tissue.

RESULTS

The lower edge of the hysterotomy had a higher collagen content than the upper, independently of whether the hysterotomy site was above or below the reflection of the bladder (P<.001 for edge level, P=.8 for bladder flap). The pyridinoline-to-collagen ratio (a reflection of collagen cross-linking) was significantly decreased in the lower edge of the hysterotomy, independently of a bladder flap (P<.001). Neither collagen birefringence nor the amount of sulfated glycosaminoglycans differed among sites. There were no significant differences in biomechanical properties between the upper and lower edges of the hysterotomy, whether or not a bladder flap was created.

CONCLUSION

The lower uterine segment of women with dystocia maintains its overall biomechanical properties despite significant quantitative and qualitative differences in fibrillar collagen between the upper and lower edge of the hysterotomy incision.

LEVEL OF EVIDENCE

II.

Prolonged labour associated with lower expression of syndecan 3 and connexin 43 in human uterine tissue

BACKGROUND

Prolonged labour is associated with greater morbidity and mortality for mother and child. Connexin 43 is a major myometrial gap junction protein found in human myometrium. Syndecan 3 seems to prevail in the human uterus among heparan sulphate proteoglycans, showing the most significant increase during labour. The aims of the present study were to investigate syndecan 3 and connexin 43 mRNA expressions and protein distributions in human uterine tissue during normal and prolonged labour.

METHODS

Uterine isthmic biopsies were collected from non-pregnant (n = 7), term pregnant women not in labour (n = 14), in normal labour (n = 7) and in prolonged labour (n = 7). mRNA levels of syndecan 3 and connexin 43 were determined by real time RT-PCR. The localization and expression were demonstrated by immunohistochemistry and confocal microscopy.

RESULTS

In women with prolonged labour, the mRNA expressions of syndecan 3 and Connexin 43 were considerably lower than the expression level at normal labour (p < 0.05). In term-pregnant tissue, the expression of syndecan 3 and connexin 43 did not differ significantly compared to non-pregnant and normal labour. The immunoreactivity of syndecan 3 was strong at normal labour, in contrast to prolonged labour, where both a weaker expression and an irregular distribution were detected. The immunoreactivity of connexin 43 increased until term and further stronger staining occurred at normal labour. At prolonged labour, the immunoreactivity was weaker and more unevenly distributed. At labour, a co-localization of syndecan 3 and connexin 43 could be demonstrated in the smooth muscle by confocal microscopy.

CONCLUSION

The high expression of syndecan 3 and connexin 43 and their co-localization to the smooth muscle bundles during normal labour, together with the significant reduction in prolonged labour, may indicate a role for these proteins in the co-ordination of myometrial contractility.

Normal labor associated with changes in uterine heparan sulfate proteoglycan expression and localization

HYPOTHESIS

Proteoglycans are well-known modulators of intercellular communication and signaling. Remodeling of the proteoglycans in the human uterus occurs throughout pregnancy, and during labor. We therefore hypothesize that heparan sulfate proteoglycans (HSPGs) play an important role in establishing normal labor. In this study HSPGs were characterized and localized in human uterine tissue.

METHODS

Uterine biopsies were obtained from four nonpregnant women, four women during elective cesarean section and four during emergency cesarean section. The biopsies were extracted using 4 m guanidinium hydrochloride (GuHCL). HSPGs were then purified by repeated ion-exchange chromatography on dehydroepiandrosterone (DEAE)-cellulose after digestion with chondroitinase ABC and finally precipitated with Alcian blue. HSPGs were identified by agarose gel electrophoresis and Western blotting. Controlled degradation of the heparan sulfate (HS) side-chains was performed using heparitinase or deglycosylation with trifluoromethanesulfonic acid (TFMS). The resulting core proteins were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and visualized by Coomassie staining. HSPGs were localized in uterine tissue by immunohistochemistry.

RESULTS

SDS-PAGE after deglycosylation indicated the presence of multiple distinct core proteins tentatively identified as syndecans 1-4 and glypican 1. Western blots confirmed the presence of these proteoglycans and also perlecan. Immunohistochemistry revealed that the HSPGs were localized mainly in the smooth muscle with few in the extracellular matrix (ECM). Syndecan 3, the dominant proteoglycan, showed the most pronounced changes during pregnancy and labor.

CONCLUSION

For the first time several heparan sulfate proteoglycans have been identified and localized in the human uterus and shown to vary in expression during pregnancy and labor. Syndecan 3 had the most outstanding features in this respect.

Maternal serum levels of dehydroepiandrosterone sulfate and labor induction in postterm pregnancies

OBJECTIVES

To study the relationship between maternal endogenous dehydroepiandrosterone sulfate (DHEAS) levels, success of labor induction, and Bishop scores in postterm pregnancies.

METHODS

There were 65 postterm pregnancies. Group 1 consisted of women spontaneously in the active phase of labor, and group 2 of women with hypotonic uterine contractions whose labor was inducted by oxytocin. Levels of DHEAS were studied from venous blood samples. Demographic data and Bishop scores were recorded.

RESULTS

The demographic characteristics of patients were similar, but DHEAS levels were higher in group 1 than in group 2 (P<0.001). Linear regression analysis showed a significant relationship between DHEAS and Bishop scores. DHEAS levels in women delivered vaginally were significantly higher than in women delivered by cesarean section. From the receiver operating characteristics (ROC) curve, DHEAS levels might determine the mode of delivery and success of labor induction; however, Bishop scores do not.

CONCLUSIONS

DHEAS levels may be an important factor influencing the efficiency of labor and the success of labor induction in postterm pregnancies.

Regional differences in water content, collagen content, and collagen degradation in the cervix of nonpregnant cows

The cow could be a suitable model for studies concerning functional changes of the cervix. However, as in many species, the bovine cervix becomes softer in texture during the follicular phase of the estrous cycle compared to the luteal phase. In the present study, we explored if changes in the collagen network take place that could be responsible for this phenomenon and if regional differences in water content, collagen content, and collagen degradation along the cross-sectional and longitudinal axes of the cervix were present. Two groups of nonpregnant animals with different progesterone status were studied. One group (n = 11) was under high progesterone influence, and the other group (n = 12) was under low progesterone influence. The water content was derived from the weight of the samples before and after lyophilization. The collagen content and the ratio of collagenous to noncollagenous proteins (hydroxyproline:proline ratio) were determined by performing amino acid analysis on hydrolyzed samples using high-performance liquid chromatography. Collagen denaturation was quantified with a colorimetric assay by determining the amount of hydroxyproline released from samples treated with alpha-chymotrypsine. The water content of the superficial layer of the submucosa was always significantly (P < 0.01) higher than the water content of the deep layer in the vaginal, mid, and uterine segments, but this was unrelated to the progesterone status of the animals. No effect of the tissue layers or of the progesterone status of the animals on the collagen content was observed, but an effect of segment was noted. The collagen content (mug/mg dry wt) in the vaginal segment of the cervix was significantly higher than in the mid (P < 0.05) and the uterine (P < 0.01) segments. The hydroxyproline:proline ratio showed the same pattern as the collagen content. The percentage of collagen denaturation in the superficial layer was always significantly (P < 0.01) higher than that in the deep layer, but no effect of the progesterone status or of the segment along the longitudinal axis was seen. It is concluded that regional differences in collagen biochemistry are present in the cervix of nonpregnant cows, which may account for the difference in firmness of different parts along the circular or the longitudinal axis of the cervix. However, differences in texture of the cervix between the two groups of cows could not be explained by differences in the collagen content, percentage of collagen denaturation, or water content.

Prediction of vaginal delivery following caesarean section for failure to progress based on the initial aberrant labour pattern

OBJECTIVE

To determine whether the pattern of cervical dilatation prior to caesarean section for 'failure to progress' can predict the outcome of subsequent labour.

STUDY DESIGN

Single hospital case note review of 171 women delivered by caesarean section for failure to progress and subsequently delivering at the same hospital. Cervicograms were categorized into one of the four patterns by an assessor blinded to the subsequent outcome. Statistical analysis was done by analysis of variance.

RESULTS

The incidence of vaginal delivery did not significantly differ between the groups.

CONCLUSION

Categorisation of failure to progress by partographic abnormality does not predict subsequent successful vaginal delivery.

Identification of the major proteoglycans from human myometrium

BACKGROUND

During pregnancy and parturition a remodeling within the extracellular matrix of the cervix and the corpus uteri occurs, which is of fundamental importance to a normal labor. The aim of this study is to identify the major proteoglycans in corpus uteri of non-pregnant subjects.

METHODS

From human uterine tissue proteoglycans were extracted and purified using CsCl-density gradient centrifugation, gel and ion-exchange chromatography. The proteoglycans were quantified and identified by Alcian Blue before and after ABC-digestion and by Western blotting.

RESULTS

The results showed that the corpus uteri contains a substantial amount of proteoglycans, 1.825 microg/mg wet weight. Decorin is dominating, constituting 63% of the total amount of proteoglycans. Heparan sulphate proteoglycans accounted for 20% and biglycan for 16%. Less than 1% consisted of the large proteoglycan versican.

CONCLUSIONS

Further investigations must be performed to provide more information of the biological role of the proteoglycans in the uterus, especially during labor, by the presence of heparan sulphate proteoglycans and the minute presence of versican which indicate that the proteoglycan composition and organization is different to that of the cervix.

Differential expressions of mRNA for proteoglycans, collagens and transforming growth factor-beta in the human cervix during pregnancy and involution

During pregnancy and involution, an extensive remodelling of the human cervical connective tissue occurs. This cervical ripening is one of the most pronounced physiological remodelling processes known in human connective tissue. To investigate how the remodelling is accomplished, the levels of mRNA for collagen I and III, versican and three small proteoglycans, biglycan, decorin and fibromodulin, were evaluated using Northern blots at different stages of cervical ripening. In the corresponding biopsies the concentration of collagen and of small and large proteoglycans were determined. The role of transforming growth factor-beta (TGF-beta) as a mediator of the remodelling process was also investigated. The concentration of collagen decreased and 1 week before partus, 50% of the nonpregnant level was attained. No further decrease was noted after partus. The mRNA for collagen I and III did, however, not decrease in the term pregnant cervix 1 week before partus. Only 20-30% decrease during the final ripening just before partus was recorded. Neither did the mRNA levels of the small proteoglycans change significantly during the ripening, despite an almost 50% decrease in the concentration of the small proteoglycans. The message for versican was, however, 5-fold increased at partus and then gradually returned to nonpregnant levels within 4 days after delivery. These changes corresponded to similar changes in the concentration of the large proteoglycan. Thus, the remodelling of the cervical connective tissue is achieved by two different mechanisms, on one hand an increased turnover of collagen and the small proteoglycans, on the other a changed transcription followed by an increased production of versican. During the involution 2- to 3-fold increases in the messages for collagen I and III, and the small proteoglycans, biglycan and decorin, corresponded to increases in the concentration of the small proteoglycans and non-extractable collagen. The message for TGF-beta was increased 2-fold immediately after delivery compared with the term pregnant state. Thus, TGF-beta may be of importance for the reconstruction of the cervix, which starts immediately after partus.

Cervical assessment by magnetic resonance imaging--its relationship to gestational age and interval to delivery

The aim of this cross-sectional study was to assess the uterine cervix in late pregnancy, using MRI, and to study its relationship to the gestational age and the time interval to delivery. 91 women with a singleton cephalic presenting fetus had MRI of the pelvis between 35 and 41 weeks. All had had one prior lower segment Caesarean section and no history of prior vaginal delivery. The cervical length, internal and external os diameter, cervical signal intensity and the angulation of the cervix with the cephalocaudal axis were measured on sagittal T2 weighted images and correlated with the gestational age and the interval from the MRI examination to delivery. It was found that the signal intensity of the cervical stroma increased with the gestational age. A higher signal intensity in the cervical stroma was associated with a shorter time interval to delivery. Deliveries after 40 weeks tended to occur more commonly in those with lower signal intensity in the cervical stroma and also in those with a smaller external os diameter. It is concluded that cervical softening as assessed on MRI correlated with gestational age and the time interval to delivery.

Tissue-specific expression of the relaxed conformation of plasminogen activator inhibitor-2 and low-density lipoprotein receptor-related protein in human term gestational tissues

The relaxed conformation of plasminogen activator inhibitor-2 (PAIr) is formed during inactivation of the matrix-degrading enzyme urokinase plasminogen activator (uPA). The presence of PAIr in tissues, therefore, indicates the in situ inhibition of uPA-mediated proteolysis. In addition, PAIr functions as a ligand for the clearance receptor low-density lipoprotein receptor-related protein (LRP), thereby promoting internalization of receptor-bound uPA-PAIr complexes from the cell surface. The rapid internalization of receptor-bound, inactivated uPA has been suggested to be characteristic of invasive cell phenotypes. The aims of this study were to characterize the immunohistochemical localization of PAIr in human term gestational tissues (amnion, choriodecidua, and placenta) and to establish its co-expression with other components of the uPA cascade. The results obtained indicate that PAIr immunoreactivity was exclusively localized to amnion epithelial cells, with only minimal staining in the underlying chorion. PAIr immunoreactivity was not detectable in any of the trophoblastic tissues examined (villous and extravillous). The tissue-specific expression of PAIr immunoreactivity was not significantly altered in association with labor onset. uPA and PAI-2 staining was localized predominantly to amnion epithelial cells, underlying chorion, and trophoblast cells of villous and extravillous tissue. Amnion and trophoblasts of extravillous and chorionic tissue showed uPAR immunoreactivity, whereas staining in placenta was absent. Immunoreactive LRP was confined to trophoblasts of the chorion, and the villous and extravillous tissue. For the first time, localization of PAIr at the tissue level has been identified. The data obtained are consistent with the hypothesis that cells of invasive phenotype, although expressing all components of the uPA cascade, do not accumulate immunoreactive PAIr, because it is rapidly internalized from the cell surface. Conversely, cells of noninvasive phenotype will accumulate PAIr immunoreactivity only in the absence of LRP expression. We propose that the presence of PAIr and the absence of LRP at the cell surface are putative markers of noninvasive phenotypes.

Simultaneous monitoring of head-to-cervix forces, intrauterine pressure and cervical dilatation during labour

In many westernized countries, the caesarean section role has now reached 15% or more, most commonly because of slow progress in labour. In order for labour to result in a vaginal delivery, the uterine cervix must dilate to allow the foetus to travel through the birth canal. This process is driven by uterine contractions, but the mechanisms by which the contractions result in cervical dilatation are still far from clear. The force exerted by the presenting part (foetal head) on the cervical tissue during contractions (head-to-cervix force, HCF) has been shown to be the variable with the best correlation with cervical dilatation. Unfortunately, the mechanism by which these two variables are related is still poorly understood. In order to investigate the relationship between head-to-cervix force, intrauterine pressure (IUP) and cervical dilatation, we have developed a system for their simultaneous and continuous monitoring during labour. The HCF is measured by using a novel intrauterine probe which is slipped alongside the foetal head so as to lie sandwiched between the latter and the cervix. The probe is fitted with six specially designed miniature force sensors, spaced 1.8 cm apart, which respond linearly and approximate the behaviour of load cells. They are interfaced with a PC by circuitry that allows auto-zeroing and drift compensation. The system enables simultaneous acquisition of intrauterine pressure and foetal heart rate (measured using a Sonicaid Meridian foetal monitor) via a serial link, together with continuous cervical dilatation measured by a caliper-like device applied to the cervix. Some preliminary data are presented, which suggest that the system can be used to investigate the role played by head-to-cervix force and intrauterine pressure in the cervix dilatation process.

Changes in rat cervical collagen during gestation and after antiprogesterone treatment as measured in vivo with light-induced autofluorescence

OBJECTIVE

This study was conducted to evaluate use of light-induced autofluorescence for measuring changes in collagen of cervical connective tissue during gestation.

STUDY DESIGN

In a conventional laboratory setting light-induced autofluorescence from the cervix of Charles-Dawley timed pregnant rats was measured in vivo. Eight distinct groups at various times of gestation were examined. Measurements were also performed on rats at day 17 of gestation 24 hours after treatment with RU 38486.

RESULTS

The amount of light-induced autofluorescence decreases significantly as pregnancy approaches term (means of the arbitrary total counts per spectrum on day 19 vs day 21 = 2.8 x 10(5) vs 1.9 x 10(5), p < 0.01) and reaches its lowest point when the pups are engaged in the cervix (day 19 vs day 22 = 2.8 x 10(5) vs 0.95 x 10(5), p < 0.001) and during delivery (day 19 vs day 22 = 2.8 x 10(5) vs 0.95 x 10(5), p < 0.001) and during delivery (day 19 vs delivery = 2.8 x 10(5) vs 0.83 x 10(5), p < 0.001). Preterm treatment with RU 38486 also caused a significant decrease in the native fluorescence compared with vehicle-injected controls (day 17 control vs day 17 RU 38486 = 2.8 x 10(5) vs 1.5 x 10(5), p < 0.001).

CONCLUSION

Significant decreases in cervical collagen at parturition parallel the results of previous studies that used various indirect methods to analyze collagen content. These data support the use of light-induced autofluorescence for detecting and studying the changes in cervical and uterine connective tissue during gestation in vivo.

Cervical ripening before medical induction of labor: a comparison of prostaglandin E2, estradiol, and oxytocin

OBJECTIVE

Our purpose was to evaluate the effectiveness of oxytocin, prostaglandin E2 intracervical gel, and estradiol cream for ripening the very unfavorable cervix in patients requiring induction of labor at term.

STUDY DESIGN

This prospective, randomized study was conducted in a population of women with a very unfavorable cervix (Bishop score < 4) requiring induction of labor. The patients received prostaglandin E2 gel (0.5 mg) intracervically (three doses 6 hours apart), 4 mg estradiol cream in the anterior fornix of the vagina (three doses 6 hours apart), or oxytocin at induction per protocol with an infusion pump.

RESULTS

Ninety-nine women were recruited into this trial and evenly distributed among the three groups. The demographics of maternal age, race, parity, gestational age, initial Bishop score, and indication for induction were similar among the groups. The incidence of cesarean deliveries was similar in the three groups with approximately 59% of pregnancies delivered abdominally. For patients undergoing abdominal delivery the maximum cervical dilatation among the oxytocin, estradiol, and prostaglandin E2 groups was similar (3.90 +/- 3.02 cm, 3.63 +/- 2.79 cm, and 4.65 +/- 2.78 cm, respectively; p > 0.05). For all patients birth weight and Apgar scores at 1 and 5 minutes were comparable across all regimens (p > 0.05). In the subset of patients delivered vaginally patients receiving oxytocin for cervical ripening had the greatest improvement in Bishop score over baseline (p = 0.023) with an improvement of 7.08 +/- 2.42.

CONCLUSION

No differences were detected among prostaglandin E2 gel, estrogen, and oxytocin in relation to cervical ripening in patients with an unfavorable cervix at term who require an induction of labor. Patients with a very unfavorable cervix at term who require delivery may benefit from serial ripening and inductions.

Changes in cervical electromyographic activity and their correlation with the cervical response to myometrial activity during labour

Intrauterine pressure, cervical dilatation and cervical electromyographic activity were recorded synchronously in five women from induction through the latent phase of labour and into the active phase. In all cases the electromyographic activity recorded in early labour was grouped into bursts synchronised with uterine and cervical contractions. Between these increases in electromyographic activity a significant background level of electrical activity was present in each case. With effacement the amount of electrical activity from the cervix was reduced, although increases in activity were noted to be synchronous with myometrial activity and, at this stage, dilatation of the cervix. This type of activity was typical of the active phase of labour until full dilatation, whilst the previous pattern typified the latent phase. The implications of these findings for the function of the cervix and the mechanism of cervical effacement are discussed.

Cervical contractions: the response of the cervix to oxytocic stimulation in the latent phase of labour

OBJECTIVE

To assess the cervical response to myometrial activity in early labour.

DESIGN

Prospective observational study.

SUBJECTS

Women requiring oxytocin stimulation in induced and spontaneous labours.

SETTING

A teaching hospital in Birmingham.

MAIN OUTCOME MEASURES

Simultaneous comparison of the cervical response to myometrial contractions was made on a cycle by cycle basis to deduce the properties of the cervix in early labour.

RESULTS

Sixty-seven patients have been monitored, of whom 63 had satisfactory cervimetry data. Thirty (47.6%) women exhibited cervical contractions in response to myometrial activity. This response was only observed at dilatations up to 4 cm. The change in behaviour coincides with the transition from latent to active phases of dilatation. The length of the latent phase of labour was significantly longer in those women who exhibited cervical contractions (P < 0.001), although the active phase was similar in the two groups (P > 0.1). The group without cervical contractions exhibited a greater degree of effacement (P < 0.05) and tended to have more dilated cervices (P < 0.01) than those who showed cervical contractions.

CONCLUSIONS

It is possible for the cervix to contract in early labour. This response may be the result of incomplete preparation of the cervix for the process of dilatation, and is seen during what is recognised as the latent phase in those women in whom the cervix is unaffected and undilated. These properties of the cervix may explain the poor results obtained from oxytocin stimulation of labour in the latent phase.