Comparison of transabdominal and transvaginal ultrasonography for the assessment of cervical length in the third trimester of pregnancy

Abstract

Objective: This study aimed to compare TA and transvaginal (TV) ultrasound assessment of cervical length (CL), as well as to assess the feasibility of the TA approach in the third trimester of pregnancy. Materials and methods: This was prospective study of low-risk women at 31–34 gestational weeks who underwent TA and TV CL measurements during a routine 3rd trimester scan. All examinations were performed by one operator who was blind to the measurements. Differences between the two methods were evaluated. Results: 240 women were initially enrolled in the study. Paired TA and TV measurements were obtained in 123 (51.3%) women. The mean TV CL was 35.2 ± 6.8 mm and the mean TA CL was 34.7 ± 6.5 mm. There was a significant correlation between the CL measured by the two different methods (r = 0.816). No significant differences were identified between the mean CL measurements of the two techniques (t = −1.360; p = 0.176). Moreover, regarding the feasibility of TA technique, it was less likely to obtain TA CL images in cases with a cephalic fetal presentation (p = 0.028). Conclusion: At 31–34 gestational weeks, with an empty bladder, the cervix can be visualized by the TA approach in only about half of the cases (51.3%). The TA CL measurements show a significant correlation with the TV ones. More research is needed to determine the potential predictive value of the TA ultrasound for preterm labor. Keywords: Cervical length, Transabdominal ultrasound, Transvaginal ultrasound