Transperineal versus endovaginal ultrasonographic examination
of the cervix in the midtrimester: A blinded comparison
John Owen, MD, Cherry Neely, RT, RDMS, and Allison Northen, RN
OBJECTIVE: Shortening of the cervix that occurs early in gestation as determined by ultrasonography has
been correlated with subsequent spontaneous preterm birth. Because previous studies have compared
transperineal and endovaginal ultrasonographic assessment of the cervix over a wide gestational age range,
we compared these methods in the midtrimester.
STUDY DESIGN: We performed a prospective, blinded comparison of endovaginal and transperineal cervi-
cal ultrasonographic assessment. Unselected gravid women at 15-23 weeks’ gestation were sequentially ex-
amined by 2 experienced sonographers using an endovaginal probe and a curvilinear probe. For each pa-
tient the initial sonographer and examination method were randomly assigned. The sonographer who
performed the second examination was blinded to the results and images from the first examination.
RESULTS: One hundred two women were studied at a mean of 19.6 weeks’ gestation. The overall inter-
method correlation was poor (
= 0.38). In 12 cases a transperineal measurement could not be obtained be-
cause of poor visualization of the required landmarks. In 33% of cases the intermethod difference in cervical
length was ≥20%.There was no correlation in the identification of funneling at the internal os and very small
correlation for the identification of a poorly developed lower uterine segment.
CONCLUSION: Transperineal ultrasonographic imaging of the cervix is an unsatisfactory alternative to an
endovaginal assessment in the midtrimester. (Am J Obstet Gynecol 1999;181:780-3.)
Key words: Endovaginal ultrasonography, transperineal ultrasonography, cervical length
Shortening of the cervix that occurs early in gestation
has been correlated with subsequent spontaneous
Because previous studies
transperineal and endovaginal ultrasonographic imaging
of the cervix over a broad gestational age range and be-
cause changes in cervical length that occur earlier in ges-
tation might be more predictive of preterm delivery,
sought to determine the correlation between these 2
methods in the midtrimester.
Material and methods
After approval by the University of Alabama at
Birmingham Investigational Review Board, this ran-
domized, prospective, observational study was per-
formed at the University Women’s Clinic, an outpatient
facility. Unselected women attending our obstetric clin-
ics who were between 15 and 24 weeks’ gestation were
recruited for the study. Gestational age was determined
by a combination of a reliable last menstrual period
and either first- or second-trimester ultrasonographic
Consenting subjects underwent both a transperineal
and an endovaginal examination of the cervix. Both exam-
inations were performed with a GE 3200 Advantage II (GE
Medical Systems, Milwaukee, Wis) unit. For the transper-
ineal examination a 5-MHz curvilinear probe was used
whereas a 7.0-MHz endovaginal probe was used for the en-
dovaginal imaging. Two dedicated sonographers (A.N.,
C.N.) performed all of the examinations sequentially in
the same session. Both sonographers had >10 years’ expe-
rience in endovaginal ultrasonography, and both had been
our center’s sonographers for the Maternal-Fetal Medicine
Units Network Preterm Prediction Study, certified by the
One sonographer (C.N.) produced
the training tape for the sonographers at the other 9 par-
ticipating university-affiliated centers.
Each of the transperineal and endovaginal examina-
tions was performed independently by 1 of the 2 sonog-
raphers. The sonographer who performed the first scan
was determined by computer-generated, blocked ran-
dom assignments contained in sequentially numbered
opaque envelopes. These also directed the type of scan
(endovaginal or transperineal) to be performed first, to
ensure that each sonographer would perform the same
number of transperineal and endovaginal examinations.
From the Division of Maternal-Fetal Medicine, Department of Obstetrics
and Gynecology, University of Alabama at Birmingham.
Presented at the Nineteenth Annual Meeting of the Society for Maternal-
Fetal Medicine, San Francisco, California, January 18-23, 1999.
Reprints not available from the authors.
Copyright © 1999 by Mosby, Inc.
0002-9378/99 $8.00 + 0 6/6/100575