The role of sonographic cervical length in labor induction at term

Predictive factors for vaginal delivery by induction of labor in uncomplicated pregnancies at 40-41 gestational weeks: A Japanese prospective single-center cohort study

AIM

We investigated cervical parameters predictive of vaginal delivery in elective labor induction among women at 40-41 gestational weeks.

METHODS

This Japanese prospective single-center cohort study was conducted between July 2019 and June 2020. We enrolled women with an uncomplicated singleton pregnancy who underwent labor induction at 40-41 gestational weeks. We analyzed background characteristics and cervical parameters, including Bishop score, cervical length, posterior cervical angle, and changes in cervical parameters before and after cervical dilatation. The endpoint was the rate of vaginal delivery.

RESULTS

Of 142 eligible participants, all 24 multiparous women underwent vaginal delivery. Among the nulliparous women (n = 118), the following categories showed significantly higher rates of vaginal delivery: Bishop scores of ≥6 before and after dilatation, compared with Bishop score <6 (adjusted prevalence ratio (aPR) [95% confidence interval (CI)]; 1.58 [1.17-2.13] and 1.56 [1.13-2.14], respectively) and cervical length of <10 and 10-20 mm before dilation, compared with cervical length of >30 mm (aPR [95% CI]; 1.47 [1.00-2.15] and 2.13 [1.42-3.18], respectively). The posterior cervical angle and other background characteristics showed no significant associations. Furthermore, women with cervical lengths of ≥20 mm before and <20 mm after dilatation showed a higher rate of vaginal delivery, compared to cervical length of ≥20 mm even after dilatation (aPR [95% CI]; 1.95 [1.19-3.20]).

CONCLUSIONS

High Bishop score, short cervical length, and changes in cervical length with dilatation are potential independent predictors of vaginal delivery following elective labor induction in nulliparous women at 40-41 gestational weeks.

The Uterocervical Angle Combined with Bishop Score as a Predictor for Successful Induction of Labor in Term Vaginal Delivery

The objective of this study was to determine the value of uterocervical angle (UCA) in predicting successful induction of labor (IOL) in singleton pregnant women compared to the Bishop score and cervical length (CL). A total of 205 normal term, singleton labor-induction cases were analyzed. Successful IOL was defined as the onset of active labor of induction. A comparative analysis was performed to evaluate the effectiveness of UCA, Bishop score, and CL in predicting IOL. Compared to the non-successful IOL group, the women in the successful IOL group had significantly wider UCA (p = 0.012) and higher Bishop score (p = 0.001); however, the CL was not significantly different (p = 0.130). UCA alone did not perform better than the Bishop score when predicting successful IOL. However, UCA combined with the Bishop score showed higher performance in predicting IOL (combined UCA > 108.4° and favorable Bishop score as sensitivity of 44.6%, specificity of 96.0%, PPV of 96.2%, and NPV of 43.6; combined UCA > 108.4° or favorable Bishop score as sensitivity of 85.7%, specificity of 50.0%, PPV of 78.7%, and NPV of 61.9). In conclusion, UCA combined with Bishop score may be an effective sonographic method for predicting successful IOL.

Role of Cervical Phosphorylated Insulin-Like Growth Factor-Binding Protein 1 (phIGFBP1) for Prediction of Successful Induction Among Primigravida with Prolonged Pregnancy

Purpose of the Study

To estimate and to compare the levels of cervical phIGFBP-1 among primigravida with prolonged pregnancy, with and without successful induction of labor (IOL).

Methods

A diagnostic study (cross-sectional study design) was conducted in our institution from November 2016 to April 2018 on 84 primigravida at ≥ 41 weeks with uncomplicated singleton pregnancy. The results were analyzed using SPSS software and receiver operating characteristics curves to determine the best cutoff using Youden Index. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), positive (+ LR) and negative likelihood ratio (- LR) were calculated. P value < 0.05 was considered significant. Logistic regression analysis was used to determine the predictive ability of the three markers for successful IOL.

Results

The cutoff level of phIGFBP-1, Bishop score (BS) and transvaginal cervical length (TVL) were 7.8 µg/l, 3 and 3.5 cm, respectively. The sensitivity, specificity, PPV, NPV, + LR and - LR of phIGFBP-1 (> 7.8 µg/l) were 0.87, 0.87, 0.89, 0.85, 6.76 and 0.15, respectively. Using logistic regression analysis, phIGFBP-1 was found to be the best predictor of successful IOL (OR 44.200; 95% CI 12.378-157.831, p < 0.001).

Conclusion

phIGFBP-1 is a strong independent predictor successful IOL as compared to TVL and BS in primigravida with prolonged pregnancy.

Uterine Cervical Change at Term Examined Using Ultrasound Elastography: A Longitudinal Study

The aim of the study was to investigate if there are changes in elastographic parameters in the cervix at term around the time of delivery and if there are differences in the parameters between women with spontaneous labor and those without labor (labor induction). Nulliparous women at 36 weeks of gestation eligible for vaginal delivery were enrolled. Cervical elastography was performed and cervical length were measured using the E-Cervix^TM system (WS80A Ultrasound System, Samsung Medison, Seoul, Korea) at each weekly antenatal visit until admission for spontaneous labor or labor induction. E-Cervix parameters of interest included elasticity contrast index (ECI), internal os strain mean level (IOS), external os strain mean level (EOS), IOS/EOS strain mean ratio, strain mean level, and hardness ratio. Regression analysis was performed using days from elastographic measurement at each visit to admission for delivery and the presence or absence of labor against cervical length, and each E-Cervix parameter fitted to a linear model for longitudinal data measured repeatedly. A total of 96 women were included in the analysis, (spontaneous labor, n = 39; labor induction, n = 57). Baseline characteristics were not different between the two groups except for cesarean delivery rate. Cervical length decreased with advancing gestation and was different between the two groups. Most elastographic parameters including ECI, IOS, EOS, strain mean, and hardness ratio were significantly different between the two groups. In addition, ECI, IOS, and strain mean values significantly increased with advancing gestation. Our longitudinal study using ultrasound elastography indicated that E-cervix parameters tended to change linearly at term near the time of admission for delivery and that there were differences in E-Cervix parameters according to the presence or absence of labor.

Recent advances in the induction of labor

The rate of labor induction is steadily increasing and, in industrialized countries, approximately one out of four pregnant women has their labor induced. Induction of labor should be considered when the benefits of prompt vaginal delivery outweigh the maternal and/or fetal risks of waiting for the spontaneous onset of labor. However, this procedure is not free of risks, which include an increase in operative vaginal or caesarean delivery and excessive uterine activity with risk of fetal heart rate abnormalities. A search for “Induction of Labor” retrieves more than 18,000 citations from 1844 to the present day. The aim of this review is to summarize the controversies concerning the indications, the methods, and the tools for evaluating the success of the procedure, with an emphasis on the scientific evidence behind each.

New techniques in evaluation of the cervix

The process of parturition is poorly understood, but the cervix clearly plays a key role. Because of this, recent research efforts have been directed at objective quantification of cervical remodeling. Investigation has focused on two basic areas: (1) quantification of tissue deformability and (2) presence, orientation, and/or concentration of microstructural components (e.g. collagen). Methods to quantify tissue deformability include strain elastography and shear wave elasticity imaging (SWEI). Methods to describe tissue microstructure include attenuation and backscatter. A single parameter is unlikely to describe the complexities of cervical remodeling, but combining related parameters should improve accuracy of cervical evaluation. This chapter reviews options for cervical tissue characterization.

Cervical Evaluation: From Ancient Medicine to Precision Medicine

Since ancient times, cervical assessment for predicting timing of delivery has relied primarily on digital (subjective) assessment of dilatation, softening, and length. To date, transvaginal ultrasound cervical length is the only one of these parameters that meets criteria for a biomarker; no objective, quantitative measure of cervical dilatation or softening has gained clinical acceptance. This review discusses how the cervix has been assessed from ancient times to the present day and how a precision medicine approach could improve understanding of not only the cervix, but also parturition in general.

Interprofessional Obstetric Ultrasound Education: Successful Development of Online Learning Modules; Case-Based Seminars; and Skills Labs for Registered and Advanced Practice Nurses, Midwives, Physicians, and Trainees

Ultrasound is an important aid in the clinical diagnosis and management of normal and complicated pregnancy and childbirth. The technology is widely applied to maternity care in the United States, where comprehensive standard ultrasound examinations are routine. Targeted scans are common and used for an increasing number of clinical indications due to emerging research and a greater availability of equipment with better image resolution at lower cost. These factors contribute to an increased demand for obstetric ultrasound education among students and providers of maternity care, despite a paucity of data to inform education program design and evaluation. To meet this demand, from 2012 to 2015 the University of California, San Francisco nurse-midwifery education program developed and implemented an interprofessional obstetric ultrasound course focused on clinical applications commonly managed by maternity care providers from different professions and disciplines. The course included matriculating students in nursing and medicine, as well as licensed practitioners such as registered and advanced practice nurses, midwives, and physicians and residents in obstetrics and gynecology and family medicine. After completing 10 online modules with a pre- and posttest of knowledge and interprofessional competencies related to teamwork and communication, trainees attended a case-based seminar and hands-on skills practicum with pregnant volunteers. The course aimed to establish a foundation for further supervised clinical training prior to independent practice of obstetric ultrasound. Course development was informed by professional guidelines and clinical and education research literature. This article describes the foundations, with a review of the challenges and solutions encountered in obstetric ultrasound education development and implementation. Our experience will inform educators who wish to facilitate obstetric ultrasound competency development among new and experienced maternity care providers in academic and clinical settings. This article is part of a special series of articles that address midwifery innovations in clinical practice, education, interprofessional collaboration, health policy, and global health.