TITLE:
Reporting cervical effacement as a percentage: How accurate is it?
AUTHORS:
Radha Malapati, Yen N. Vuong, Tuan M. Nguyen
KEYWORDS:
Cervical Effacement; Cervical Length; Transvaginal Ultrasound
JOURNAL NAME:
Open Journal of Obstetrics and Gynecology,
Vol.3 No.7,
September
18,
2013
ABSTRACT:
Objective:
To evaluate the accuracy of cervical effacement reported as a percentage by
digital cervical exams using cervical length determined by transvaginal
ultrasonography as a standard. Methods: Records of pregnant women who had a
digital cervical exam and subsequent transvaginal ultrasound scan for cervical
length between January 2005 and December 2008 were reviewed. Digital cervical
exams were performed by different examiners. Transvaginal ultrasound was
performed by one examiner who did not perform any of the digital exams.
Cervical effacements were recorded as a percentage and cervical lengths were
measured in centimeters. Results: A total of 173 women met the study criteria.
Average cervical length for 0% effacement was 3.3 ± 1.1 cm (0.8 - 5.0 cm);
20% effacement, 1.6 ± 1.0 cm (0.9 - 3.0 cm); 25% effacement,
2.2 ± 0.2 cm (2.0 - 2.3 cm); 30% effacement, 2.6 ± 0.4 cm (2.1 - 3.0 cm); 40% effacement, 3.0 ± 0.4 cm (2.6 - 3.4
cm); 50% effacement, 2.4 ± 1.1
cm (0.6 - 4.6 cm);
60% effacement, 2.3 ± 1.4 cm (0.7 - 4.3 cm); 70%
effacement, 2.2 ± 0.8 cm (1.1 - 3.3 cm); 75%
effacement, 1.7 ± 1.4 cm (0.7 - 2.7 cm); 80% effacement,
2.0 ± 0.9 cm (0.6 - 4.4 cm); 90% effacement, 0.7 ± 0.4 cm (0.4 - 0.9 cm); 100% effacement, 1.2 ± 1.5 cm (0.3 - 3.0 cm).
The coefficient of variation ranges from 10% - 124%. Conclusion: The
traditional method of reporting cervical effacement as a percentage is
unacceptably inaccurate compared to the actual cervical length determined by
vaginal probe ultrasound.