It is about time. The advantage of transabdominal cervical length screening

Intra-Sonographer Correlation Between Transabdominal and Transvaginal Cervical Length Measurements and Associated Patient Demographics

OBJECTIVES

To assess transvaginal (TV) and transabdominal (TA) cervical length (CL) measurements' variability and patient factors associated with TA CL accuracy. We hypothesized that patient factors would affect the accuracy of TA CL.

METHODS

This was a prospective cohort study. During anatomy ultrasound, TA and TV CL measurements were obtained, distance from placental edge to internal cervical os assessed, and demographic questionnaires completed. Patients between 18 to 22 weeks and 6 days were included and those <18 year old or with a twin gestation were excluded. TA CL >0.5 cm different from TV length was considered inaccurate.

RESULTS

A total of 530 patients were included. Exactly 18.7% had a prior cesarean, 9.8% a preterm birth, and 2.2% a cervical procedure. Mean age and BMI were 31.1 years and 27.8 kg/m2 . Median number of living children was one. Median TA and TV CL were 3.42 and 3.53 cm. Exactly 36% (95% CI: 32-40%) of TA CL measurements were inaccurate. CL of 3.4 cm corresponded to a mean difference of zero between TA and TV CL. TA ultrasound had a sensitivity of 25% and a specificity of 98.5% to detect TV CL <2.5 cm. On multivariable analyses, Hispanic ethnicity was associated with inaccurate TA measurement (OR 0.48, 95% CI: 0.24-0.96, P = .04).

CONCLUSIONS

On average, TA CL underestimates TV CL when TV CL >3.40 cm and overestimates TV CL when TV CL <3.40 cm. Additional co-variates did not impact accuracy. TA ultrasound has low sensitivity to predict short cervix. Relying solely on TA CL to identify those who need intervention may miss diagnoses. It may be reasonable to develop protocols in which TV CL is used for TA CL <3.4 cm.

The perceptions of obstetric care providers about cervical length screening for preterm birth prevention

BACKGROUND

Routine cervical length (CL) measurement at the mid-pregnancy ultrasound is a central recommendation of the Western Australian Preterm Birth Prevention Initiative (Initiative).

AIM

To evaluate the perceptions and changes in practice of Western Australian obstetric care providers regarding routine CL screening for preterm birth (PTB) prevention following the Initiative introduction.

METHODS

Two self-administered questionnaires were completed by providers from a range of practices. The first was during site visits with the Initiative Outreach team in 2015-2016. The questionnaire was re-issued in 2021 via online dissemination. Participant demographic data and opinions on CL screening for PTB prevention were collected.

RESULTS

Two hundred and fourteen providers participated in 2015-2016 and 109 in 2021. In both surveys, providers were more likely to discuss transvaginal CL screening with high-risk women (48.1%, 76.1%; P < 0.001) compared with low-risk (7.5%, 18.3%; P = 0.002) and the importance of CL screening (13.5%, 40.4%; P < 0.001), in 2015-2016 and 2021, respectively. Responses relating to CL screening, including what constitutes a short cervix on ultrasound were varied. A transabdominal CL <35 mm was classified as short by 46.2% and 37.6% and <25 mm on transvaginal ultrasound by 49.1% and 64.2%, in the respective surveys. Most providers ceased progesterone (68.6%, 75.2%) at >28 weeks gestation.

CONCLUSIONS

Providers focused on women with overt PTB risk factors, rather than a universal CL screening approach. Although there was improvement between the surveys, the definition of what constitutes a short cervix on ultrasound and how to treat and monitor women with a short CL remained varied.