Transvaginal ultrasound of cervical length and its correlation to digital cervical examination, time to spontaneous labor and mode of delivery

Sonographic measurement of cervical length and head perineum distance before labor to predict time of delivery

OBJECTIVES

This was an observational study on cervical length and head perineum distance and the prediction of time of delivery. One-hundred and twenty-five nulliparous women with uncomplicated, term, singleton pregnancy were recruited when they presented to the labor ward with show or infrequent painful uterine contractions (less than three contractions in ten minutes on a 30 min cardiotocogram). Apart from digital vaginal examination to assess cervical length and dilatation, sonographic cervical length and head perineum distance were measured by two-dimensional ultrasound. We compared women who delivered within 72 h of presentation of labor symptoms, with women who did not. After excluding ten women whose labor was induced and delivered within 72 h of presentation, one hundred and fifteen women were included for final data analysis.

MAIN FINDINGS

Forty-nine women (42.6%) delivered while sixty-six women (57.4%) remained undelivered at 72 h of presentation of symptoms of labor. There was no statistically significant difference between the two groups on age, presence of show, contractions, fetal head station and presentation and mode of delivery. For the group who had delivered within 72 h of presentation of labor symptoms, the mean sonographic cervical length was 1.87 cm ± 0.62 cm, while the head perineum distance was 6.01 cm ± 1.15 cm. For the other group, the mean sonographic cervical length was 2.10 cm ± 0.83 cm; head perineum distance was 6.03 cm ± 1.18 cm. There was no statistically significant difference between the groups for both sonographic cervical length (p = .90); and head perineum distance (p = .08). We also compared the cervical length measured by digital vaginal examination versus sonography. The median sonographic measurements were 1.47 cm, 2.11 cm and 2.79 cm at "1 cm," "2 cm" and "3 cm" digital vaginal measurement, respectively. However, there was extensive overlap between digitally and sonographically measured cervical length. Prediction accuracy of cervical length and head perineum distance was poor. The area under curve (AUC) of receiver operating characteristic (ROC) curve were 0.433 for sonographic cervical length and 0.501 for HPD.

CONCLUSION

Transperineal sonographical assessment of cervical length and head perineum distance before labor was not useful in predicting the time of delivery. However, it can be explored as an alternative assessment method when digital vaginal examination is not preferred.

Predictive factors of labour onset using ultrasonography

We analysed the effectiveness of transvaginal ultrasonographic and foetal/maternal pulse Doppler findings as predictors of labour onset within 1 week. We included 22 single normal pregnancies and evaluated the one-point and short- and long-term differences in uterine artery pulsatility index (PI), umbilical artery PI, middle cerebral artery PI (MCA-PI), peak systolic velocity, and cervical length (CL). Presence of funnelling and membrane separation over the internal cervical os was evaluated. Significant changes were observed in the one-point measurement of and short-term and long-term differences in CL, the one-point measurement of and long-term difference in MCA-PI, and the presence of membrane separation (Grade 2). In multivariate analysis, the significant predictors were short-term differences in CL (odds ratio [OR]: 5.27), long-term differences in MCA-PI (OR: 13.3), and presence of membrane separation (Grade 2) (OR: 5.38). Transvaginal ultrasonographic and foetal pulse Doppler findings were effective predictors of labour onset within 1 week.Impact statementWhat is already known on this subject? Parameters reported to predict labour onset include the Bishop score, cervical length, decreased long-term cervical length, funnelling of the internal cervical os, and adrenal gland volume.What do the results of this study add? Short-term changes in cervical length, long-term changes in middle cerebral artery pulsatility index, and the presence of membrane separation Grade 2 were found to be useful predictive factors of labour onset in this study.What are the implications of these findings for clinical practice and/or further research? The prediction of labour onset enables clinicians to properly manage pregnancy and delivery considering maternal and foetal conditions.

Relationship between detection of the cervical gland area during the late third trimester and necessity for induction of labor to prevent post-term delivery

OBJECTIVES

With the maturation of the cervical canal during pregnancy, the cervical gland area (CGA) as observed on transvaginal ultrasonography is gradually obscured. The aim of this study was to elucidate the significance of CGA in the late third trimester as a determinant of the outcome of labor.

METHODS

We investigated 123 primiparous women with singleton pregnancies at 36-41 weeks' gestation. The women were divided into two groups: a normal delivery group (93 women), which had vaginal delivery without medical intervention, and an induction of labor group (30 women), which required induction of labor after 41 weeks and 0 day. At outpatient prenatal checkups, the Bishop score (BS) was assessed by pelvic examination, and cervical length (CL) and CGA were evaluated by transvaginal ultrasonography. The relationship between each parameter and induction of labor was retrospectively determined and compared.

RESULTS

Time-dependent assessment of each outcome determinant showed that the CGA detection rate was higher and the CL was longer in the induction of labor group from 3 weeks to 1 week before delivery at a significant level (P < 0.05); however, the BS was significantly lower in the induction of labor group only at 1 week before delivery (P < 0.05). When multiple logistic regression analysis of the necessity of induction of labor was conducted using BS, CL, and CGA parameters as explanatory variables at 1 week before delivery, CGA alone was shown to be an independent predictor of induction of labor (OR = 6.1, 95 % CI 2.3-16.2).

CONCLUSION

The present study suggests that in the late third trimester, evaluation of CGA with transvaginal ultrasonography is most useful in predicting the necessity of induction of labor to prevent post-term delivery.