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.