Comparison of Ultrasonographic Transabdominal and Transvaginal Measurements in Second Trimester Cervical Length Screening: Reliability of Transabdominal Measurement: A Prospective Study

To investigate the reliability of transabdominal ultrasonography (TAUS), which can be used as an alternative to transvaginal ultrasonography (TVUS), which is a gold standard method in cervical length measurement. The study also aimed to determine the cut-off values for TAUS that can predict the short cervix detected in TVUS. Material and Methods: The prospective study included 204 pregnant women. The cervical lengths (CL) of the patients were measured using TAUS and TVUS. The sensitivity, specificity, positive predictive value, and negative predictive values of the measurement methods were calculated. The TVUS CL threshold value used to define the short cervix was determined as <25 mm. Results: TAUS bladder-full CL measurements were statistically and significantly higher than bladder-empty TAUS measurements. A positive correlation was detected between the TVUS and TAUS CL measurements. The sensitivity of the TAUS bladder-full method was found to be 25% in detecting the short cervix with a specificity of 99.5%. The sensitivity of the TAUS bladder-empty method was found to be 50% with a specificity of 99.5%. The cut-off values for TVUS short cervix prediction were found to be 28 mm for TAUS bladder empty and 32 mm for TAUS bladder full. Conclusion: We recommend that TAUS be performed first in low-risk patients regarding preterm birth. When the CL is measured as 32 mm with a full bladder and 28 mm with an empty bladder in TAUS measurements, we should suspect a short CL and evaluate it with TVUS.