Ultrasonography for cervical length measurement: agreement between transvaginal and translabial techniques

Transperineal ultrasound in routine uterine cervix measurement

PURPOSE

Transvaginal ultrasound (TVUS) is used in routine practice to evaluate cervical length (CL). This technique is nevertheless invasive and often viewed as uncomfortable, which is less the case with transperineal ultrasound (TPUS). This study was conducted in light of recent technological improvements in the ultrasound field to evaluate whether TPUS could be used as an alternative to TVUS in CL assessment.

METHODS

This was a prospective single-blind study. Pregnant women requiring CL measurement during their emergency consultation were offered a second assessment by TPUS after an initial TVUS. TPUS was performed by a third-year OBGYN resident, unaware of the CL measurement obtained via TVUS.

RESULTS

Seventy-three women were included. The mean ∂ was 0.59 mm. The interclass Pearson correlation coefficient between the two techniques was 0.8987 (95% CI [0.8429; 0.9353]). None of the tested factors were found to be associated with a difference between TPUS and TVUS CL measurements. ROC curve analysis indicated that a transperineal CL cut-off measurement of 24.9 mm was predictive of a transvaginal CL measurement below 25 mm. This threshold enabled a 95% sensitivity [75.1-99.9%] and a 100% specificity [93.3-100%] for the TPUS CL measurement technique.

CONCLUSION

TPUS should be acknowledged as a reliable alternative to TVUS for CL assessment in routine every day practice.

Cervical length for predicting preterm birth and a comparison of ultrasonic measurement techniques

Introduction: Preterm birth is the leading cause of neonatal morbidity and mortality not attributable to congenital anomalies or aneuploidy. It has been shown that a shortened cervix is a powerful indicator of preterm births in women with singleton and twin gestations - the shorter the cervical length, the higher the risk of spontaneous preterm birth. Ultrasound measurements of the cervix are a more accurate way of determining cervical length (CL) than using a digital method. Background: There are three approaches that may be used to perform ultrasound measurements of the cervix; these are the transabdominal (TA), transperineal (TP) and the transvaginal (TV) approach. The TV approach is considered to be the gold standard. In women who are considered to be at a high risk of preterm birth it is now recommended that the cervix is measured at the mid-trimester ultrasound using the TV ultrasound approach. For women considered to be at a historical low risk the TV scan is not recommended, however it has been found that many women who deliver a preterm baby have no known risk factors. Conclusion: There is contradictory evidence in the literature with regard to the correlation between TA, TP and TV measurements. This article provides an overview of these three approaches with a focus on the clinical value for the assessment of the maternal cervix.

Additional effects of the cervical length measurement in women with preterm contractions: a systematic review

Purpose

Transvaginal cervical length measurement in women with symptoms of preterm labor has been used to decide if treatment is necessary. Cervical length measurement may also have additional effects on patients, such as providing reassurance, although the evidence to support this is unclear. We explored and summarized to what extent additional effects of cervical length measurement in women with threatened preterm labor have been reported in the clinical literature and what the magnitude of these effects was.

Methods

We performed a systematic review of the literature to identify articles reporting on cervical length measurements in women with symptoms of preterm labor. We assessed whether these articles reported patient outcomes other than preterm delivery.

Results

The electronic and hand search resulted in 764 articles, of which 172 met initial criteria for further eligibility assessment. We found 12 articles that reported additional effects of cervical length measurement in symptomatic women, such as the reassurance or the sensory consequences related to the transvaginal procedure. None of the articles quantified such additional effects.

Conclusions

There appears to be a gap between the presumed effects of cervical length measurement on patient outcomes, such as patients’ reassurance, and the actual assessment of these effects during test evaluations. We suggest that future evaluations of prognostic preterm labor tests include a comprehensive assessment of patient outcomes.

Methods of sonographic cervical length measurement in pregnancy: A review of the literature

In this review we give an overview of the methods and pitfalls in cervical length measurements. We compared the different techniques and investigated factors that influence visualization of the cervix. The data in this overview may be used to establish guidelines in clinical practice.

Transperineal versus transvaginal ultrasonographic evaluation of the cervix at each trimester in normal pregnant women

AIMS

To compare transvaginal and transperineal ultrasonography in the assessment of cervical length and cervical changes in normal gravid patients at each trimester.

METHODS

Transperineal and transvaginal ultrasonographic cervical length was measured on 104 asymptomatic pregnant women between 10 and 14, 20-24, and 30-34 weeks' gestation and the presence of a funnel was also noted. The study used the McNemar chi2 test to assess the difference between two methods in their ability to obtain a measurement, and the Pearson correlation coefficient to determine the relationship between the paired transperineal and transvaginal cervical lengths.

RESULTS

Cervical length measurements were obtained by transvaginal ultrasonography in all 104 patients and by transperineal ultrasonography in 101 patients (97.1%) (P = 0.1). By gestational age, the greatest length discrepancy (2.8 mm) between the two ultrasonographic methods was found at 10-14 weeks (P < 0.001). At 20-24 and 30-34 weeks' gestation, the mean length differences were less than 1 mm (P < 0.01 and P = 0.337, respectively). Cervical funnelling was observed in 16 patients by both methods, whereas in two patients from the 20-24 week gestational age group, funelling was observed by transvaginal ultrasonography and not by transperineal ultrasonography.

CONCLUSIONS

Cervical length measurements by transperineal ultrasonography show good correlation with transvaginal ultrasonographic measurements and it is a satisfactory alternative to a transvaginal evaluation of the cervix throughout pregnancy.

Role of ultrasound in screening patients at risk for preterm delivery

The ultrasound assessment of the cervix has contributed to the understanding of the pathways to preterm birth. Transvaginal ultrasound measurement of the cervix provides an objective and noninvasive tool for the evaluation of cervical status. Despite widespread use of this procedure, standardization of measurement indications, technique, and interval between examinations has not been achieved. The American College of Radiology has recently recommended that the cervix and lower uterine segment be imaged as part of every obstetric ultra-sound examination in the second trimester. These guidelines specifically suggest a search for a short cervix (less than 30 mm) or funneling. The expert panel on women's imaging further recommended evaluating the cervix sonographically on both the initial examination and all follow-up examinations for twin gestations. The American Institute of Ultrasound in Medicine guidelines indicate that evaluation of the uterus, including cervix, should be performed, but does not indicate specifically that the cervix should be measured. In contrast, the American College of Obstetricians and Gynecologists, although recognizing that cervical length assessment may be helpful in predicting the risk of preterm delivery (particularly from a negative predictive value), does not recommend routine use of cervical length measurement because of the lack of proved treatment or intervention methods. A review of the literature suggests that at the time of this writing the role of routine screening of low-risk women with cervical length assessment by ultrasound is not supported. In contrast, in women at risk for preterm delivery(eg, women with a prior history of preterm birth or women with multiple gestations) cervical length assessment may be useful for its negative predictive value. At present, however, there is no therapeutic intervention that has been proved to decrease the risk of preterm delivery in women with a documented cervix on ultrasound.

Cervical screening for preterm delivery

The ability of sonographic cervical length screening to detect those at risk of spontaneous preterm delivery has been extensively explored over the past few years. This applies both to high-risk and low-risk groups. Cervical length measurement appears to be superior to biochemical, microbiological or hormonal methods of screening. The screening technique has been standardized, but the cervical length for intervention and the timing and nature of intervention have not been defined. Cervical cerclage appears to be of use to prevent or arrest the progress of cervical dilation in high-risk cases, but the management of the screen-positive low-risk case has yet to be determined. Future management may be stratified according to actual cervical length, and prospective randomized trials of treatment for the short cervix are needed.