Correlation of uterine cervical length measurement from transabdominal, transperineal and transvaginal ultrasonography.

Objective: To investigate the feasibility of transperineal ultrasonography for uterine cervical assessment by determining the correlation of uterine cervical length measurement from transabdominal, transperineal and transvaginal ultrasonography and comparing discomfort arising from each technique.
Material and Method: Fifty pregnant women of 37 weeks' gestation or later who gave consent participated in this research. They had no exclusion criteria, which were listed as the following: preterm premature rupture of membranes, previous cervical surgery, undiagnosed vaginal bleeding, and true labor pain. They all underwent transabdominal (3.5-MHz curvilinear transducer), transperineal (3.5-MHz curvilinear transducer) and transvaginal ultrasonography (7.5-MHz curvilinear endovaginal transducer). The uterine cervical length was measured from the straight line between the external and internal os. If either of the external or internal os was not clearly demonstrated, the authors would justify the cervical length as non-measurable. Measurement in each technique was performed twice and the mean cervical length was used for data analysis. Discomfort arising from each technique was evaluated by visual analog scale.
Results: Uterine cervical length was measurable in 23 (46%), 49 (98%) and in all cases by transabdominal, transperineal and transvaginal ultrasonography respectively. In the transabdominal technique, no significant differences in woman's age, weight, body-mass index and parity were observed between measurable and non-measurable cases. Significant correlation was demonstrated between transperineal and transvaginal ultrasound (r = 0.73, p < 0.01). A significantly higher discomfort score was demonstrated in transvaginal ultrasonography, but no significant difference in discomfort score was found between transabdominal and transperineal ultrasonography.
Conclusion: Transperineal ultrasonography is feasible for acceptable uterine cervical visualization with only slight discomfort to the patients.