Use of a Pocket-device Point-of-care Ultrasound to Assess Cervical Dilation in Labor: Correlation and Patient Experience
Phase: NA
Conditions: Cervix; Pregnancy
Sponsor: Baylor College of Medicine

SOUND CHECK-CORRELATION BETWEEN TRANSPERINEAL AND 
DIGITAL CERVICAL EXAM USING A POCKET ULTRASOUND IN 3RD 
TRIMESTER PREGNANCY 
NCT05260333 
12/9/2021 
 
 

 Protocol & Statistical Analysis Plan 
 
Patients in the third trimester that present to the obstetrical triage for assessment of 
labor (contractions or rupture membranes) as well as patients admitted for labor and 
delivery will be approached. After informed consent is obtained, Dr. Connell or I will 
perform a transperineal ultrasound (TPUS) using the glove-covered Butterfly iQ+. An 
independent, blinded examiner will then perform a traditional digital cervical exam 
(DCE). The study PI's will be blinded to the DCE measurement until the end of the 
study. The patient will act as their own control. The patient will then be asked to score 
discomfort on a scale of 0-3 and preference for a method, if any. After 30 patients are 
enrolled, the PI's will compare the TPUS dilation measurements to the DCE dilation 
measurements and calculate a simple correlation. The discomfort scale will be 
analyzed using a Wilcoxon Signed Rank test. 
Inclusion Criteria: 
Pregnant women in the third trimester presenting for assessment of labor or admitted 
for labor and delivery. 
Exclusion Criteria: 
Second trimester (less than 28 weeks) BMI>50 Does not wish to participate 
Patients in the 3rd trimester that require a digital cervical exam (DCE) for assessment 
of labor will be approached. After informed consent is obtained, one of two study 
investigators will perform a transperineal ultrasound (TPUS) using the glove-covered 
Butterfly iQ+ probe. The Butterfly iQ+ does not have a transperineal probe or setting, 
therefore, the "bladder" preset setting will be used. The "bladder" setting has been 
predetermined to provide the best cervical images. This pocket ultrasound is FDA-
approved and is the standard of care for point of care ultrasounds in many institutions 
and is already used in our department. The TPUS will be performed by 1 of the 2 
investigators with digital calipers. There will be 3 measurements: dilation, effacement, 
and station. The dilation measurements with be made from the inside margins of the 
cervix . Effacement will be measured by marking the thinnest and most easily imaged 
lip of the cervix. Zero station will be assumed to be 5 cm above the perineum, with 
distances from 6-10 cm corresponding to -1 to -5 station clinically. An independent, 
blinded examiner will then perform a traditional digital cervical exam, which will be 
recorded in EPIC. The study investigators will be blinded to the DCE measurement 
until the end of the study. The patient will act as their own control. Additionally, we 
will collect EGA, race, ethnicity, age, BMI, and indication for assessment of the 

cervix. The patient will then be asked to score discomfort on a scale of 0-3 (none-
extremely). They will then be asked to state if they preferred the TPUS, DCE or have 
no preference. At the end of the study the TPUS exams will be compared to the DCE, 
and a simple correlation will be calculated.  
Data Analysis 
We chose a simple correlation r (r=0.5). Using a two-tailed test, 5% significance level 
test (α=0.05) with power 80% power (β=0.2), the required sample size is 
approximately (n=29). 
For the primary outcome, we will use the two-tailed test. For the secondary outcome 
(patient experience), we will use the Wilcoxon Signed Rank test.