Dynamics of cervical remodeling during pregnancy and parturition: Mechanisms and current concepts
ABSTRACT The cervix serves as a protective barrier from invading microorganisms and as a structural barrier to delivery of the fetus. Among all biological processes, the phenomenal connective tissue remodeling that occurs in the cervix during and after parturition is unparalleled in scope and magnitude. The process of connective tissue remodeling in the cervix during pregnancy occurs in four stages: softening, ripening, dilation, and repair. Although overlapping in time, each stage is uniquely regulated. Results from studies using serial measurements of cervical length indicate that cervical ripening precedes myometrial contractions of labor by several weeks, suggesting that parturition in women is a process of long duration and that uterine contractions of labor are late events in the parturition process. A clear understanding of the biologic mechanisms that regulate cervical remodeling during pregnancy is needed to influence the preterm birth rate and to develop strategies to prevent preterm dilation of the cervix.
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ABSTRACT: Shear wave speed (SWS) estimation is a noninvasive technique used to assess tissue properties. This could be a valuable tool in understanding changes that occur in the cervix during pregnancy and contribute to approaches for the prediction and prevention of preterm birth. The purpose of this study was to explore sources of biological variability in the normal non-pregnant cervix using shear wave speed estimation. Hysterectomy samples were collected (n = 22), a subset of which were ripened (n = 13). Multiple SWS measurements were made longitudinally along the cervical canal at 4-5 locations on both anterior and posterior halves of the cervix. Statistical tests were performed to determine significance of SWS as a function of position along the canal, anterior vs. posterior, ripened vs. unripened and variability among cervical samples using a linear mixed model. We found that SWS estimates monotonically increased from distal to proximal longitudinally along the cervix and varied anterior to posterior. All variables in the model were found to be significant (p<;0.05) using a likelihood ratio F-test to assess validity of fit.2013 IEEE International Ultrasonics Symposium (IUS); 07/2013
Conference Paper: A Summary Measure of Backscatter Anisotropy in the Non-Pregnant Cervix[Show abstract] [Hide abstract]
ABSTRACT: The uterine cervix contains pseudo-aligned and crosslinked collagen. As the cervix softens during pregnancy in preparation for childbirth, the crosslinks degrade and the collagen becomes disordered, resulting in softening (“ripening”). Preterm birth is associated with preterm cervical change, and therefore early detection of this process could allow earlier intervention. Previous studies have demonstrated that acoustic backscatter with steered beams can demonstrate an excess loss in backscattered power (beyond that observed for spherical scatterers) that is indicative of the presence of aligned scattering structures. We sought to determine whether we could develop a metric for objectively analyzing collagen organization in human (nonpregnant) cervical specimens. Hysterectomy specimens were obtained from 36 subjects, 12 of whom were ripened. A summary metric, S, of eBSPL surface plots incorporates their symmetry and the total eBSPL. The two-sample Kolmogorov-Smirnov test for comparison of the S values for unripened versus ripened specimens confirmed a statistically significant difference between ripened and unripened specimens (p=0.019). However, more development and testing is needed before such a metric can be useful in detecting cervical ripening.2013 IEEE International Ultrasonics Symposium (IUS); 07/2013
Conference Paper: Detecting cervical softness with shear wave speed estimation[Show abstract] [Hide abstract]
ABSTRACT: Cervical remodeling begins early and the cervix progressively softens throughout pregnancy. Premature changes may be associated with preterm birth, but there is currently no clinical objective method for assessing the softness of the cervix. Shear wave speed estimation is a noninvasive technique to evaluate tissue mechanical properties. The goal of this study is to determine the discriminatory ability of shear wave speed estimation to detect differences between ripened/softened and unripened cervix samples. Hysterectomy samples (n = 22), a subset of which were ripened (n = 13), were collected from non-pregnant women. The samples were scanned with a 9L4 linear array transducer after excision parallel to the endocervical canal at the mid position along the length of the canal on both anterior and posterior halves. T-tests and receiver operating characteristics (ROC) were used to analyze the performance of SWS estimates. The SWS estimates for the unripened group at the mid position were 3.45±0.95 m/s (anterior) and 3.56±0.92 m/s (posterior), and 2.11±0.45 m/s (anterior) and 2.68±0.57m/s (posterior) for the ripened (p<;0.001). The corresponding area under the curve (AUC) were 0.91 for anterior and 0.84 for posterior. Our results suggest that shear wave speed estimation may be a potential research and diagnostic tool for quantification of cervical stiffness/softness.2013 IEEE International Ultrasonics Symposium (IUS); 07/2013