Transcervical Balloon Compared to Osmotic Dilators Prior to Surgical Abortion: a Non-Inferiority Randomized Trial
Phase: NA
Conditions: Abortion, Second Trimester
Sponsor: Stanford University

 
 
 
 
Transcervical Balloon Compared to Osmotic Dilators Prior to Surgical 
Abortion: a Non-Inferiority Randomized Trial   
Study Protocol and Statistical Analysis Plan 
NCT05099991 
January 25, 2022 

Protocol 
 
Fellow: 
, MD 
Fellowship site: Stanford University 
Fellowship Director: 
, MD MS 
Additional Research Mentors: 
 MD MPH; 
, MD MS; 
 
 MD MSHP; 
, MD MS; 
, MD 
 
Project Title: Transcervical Balloon compared to Osmotic Dilators prior to Surgical Abortion: a 
Non-Inferiority Randomized Trial 
 
We will conduct an unblinded, randomized, non-inferiority trial of 40 participants undergoing 
second trimester abortion between 18 and 23 weeks of gestation at Stanford Health Care. 
Participants will be approached during their initial consultation for abortion, after consent for 
the abortion has been obtained. They will sign consent and be randomized on the day of 
cervical preparation, one day prior to their D&E. We will use 1:1 randomization using a 
computer-generated variable block sequence to ensure balance of treatment groups.  
 
We will include participants of at least 18 years of age presenting to clinic for second trimester 
abortion at 18 to 23 weeks and 6 days gestation confirmed by ultrasound (which will include 17 
weeks and 6 days gestation on day of cervical preparation, one day prior to D&E, with or 
without digoxin). We will include participants who are able to provide informed consent and 
comply with study protocol, English or Spanish-speaking, and a candidate for outpatient 
cervical preparation. Exclusion criteria will include anyone with an allergy to misoprostol, 
mifepristone or any study medication, premature rupture of membranes, intrauterine fetal 
demise, placenta previa, suspected abnormal placentation or evidence of infection at the time 
of enrollment. Participants will be excluded on day of cervical preparation, after 
randomization, if their initial cervical exam is 2cm dilated and 50% effaced or more.  
 
Participants randomized to the osmotic dilator group will receive between 2 to 5 Dilapan-S 
using Table 1 as guidance, depending on gestational age. Those randomized to the Foley 
balloon group will have a Foley catheter inserted until the balloon lies beyond the internal os 
that will be filled with 30 mL of sterile water or saline.1–3  
 
Placement of balloon or osmotic dilators will be performed in dorsal lithotomy position, with 
use of a speculum, standard 10-12mL paracervical block, and tenaculum or atraumatic grasper 
with use of adjunct initial dilation if needed (ie: os finder, sound). Adjunctive medications will 
be used based on our cervical preparation protocol (Table 1). Participants will receive 
mifepristone 200mg orally within 1 hour of osmotic dilator/balloon placement.4,5  All 
participants will receive misoprostol 400 ug buccal 2-3 hours prior to their scheduled D&E.5,6 
Per our institutional practices, participants over 22 weeks gestation will be offered digoxin for 
feticide, administered upon request in earlier gestations, and use will be recorded. If the 
participant receives digoxin, it will be administered after dilator placement, and after the 
participant is asked about their pain level. Although downward traction applied to the balloon 

has been associated with a shorter time to expulsion, it has been associated with more pain 
and bleeding.3,7. Given these unfavorable effects, and the potential challenges of maintaining 
downward traction as an outpatient, initial gentle traction will be applied with the catheter 
taped to the participant’s medial thigh; however, participants will not be instructed to maintain 
tension as an outpatient.  
 
Our primary outcome will be procedure duration (speculum insertion to removal). Prior studies 
have demonstrated that procedure time is normally distributed with a standard deviation of 5 
minutes.8,9 We will define 5 minutes as our non-inferiority threshold. To achieve 80% power 
with a one-sided alpha 2.5% to detect this difference, we require 16 participants per group and 
32 total. Anticipating loss to follow up, we will plan to enroll 20 participants per group. 
  
Description of the data to be collected and what statistical procedures will be used to answer 
the hypothesis and research question. 
 
Day prior to abortion: We will collect contact information, baseline demographics and history 
(age, BMI, race, education, indication for abortion, parity, mode of prior deliveries, prior 
abortion, prior osmotic dilators, number of weeks gestation, prior cervical procedures, prior 
surgeries, medical problems, medications, allergies). We will record baseline pain prior to 
positioning patient for cervical preparation. We will collect information on initial digital cervical 
exam (dilation/effacement/consistency/position), time of osmotic dilator or balloon placement, 
number of Dilapan-S if applicable, dilator placement duration, provider ease of placement by 
VAS, participant reported pain after procedure (within 5 minutes of speculum removal) by VAS, 
reported maximum pain during procedure by VAS. If digoxin is administered, it will only be 
done after dilator placement and all pain levels are collected.  
 
Day of abortion. Preoperative information will also include maximum reported pain overnight 
prior to misoprostol administration, time of misoprostol intake, documentation of time of 
osmotic dilator or Foley balloon removal or expulsion (total time with dilator in place), 
symptoms overnight, reported maximum pain overnight by VAS, reported number of ibuprofen 
and Norco pills taken overnight, patient satisfaction by VAS, and if they would recommend their 
type of dilation for future patients.  
 
Abortion: We will record digital cervical exam (dilation/effacement/consistency/position), need 
for additional mechanical dilation, total duration of procedure (speculum insertion to removal), 
time from insertion of first intrauterine instrument (suction cannula or forceps) to final removal 
of intrauterine instrument (suction cannula), type of anesthesia, primary surgeon level (senior 
resident in their last half of final year, fellow, faculty), surgeon satisfaction with dilation by VAS, 
surgeon’s ease with procedure by VAS, EBL, complications (cervical laceration, hemorrhage, 
perforation, infection, intact expulsion).  
 
Post procedure: Prior to discharge, at least 60 minutes but before 120 minutes after procedure 
(time to be recorded), participants will be asked about overall experience by VAS, and current 
and maximum pain since procedure by VAS.  

Table 1: Cervical preparation protocol based on gestational weeks 
 
 
 
Gestational 
weeks 
Misoprostol 
(400mcg buccal 
2-3h prior to 
D&E) 
Mifepristone 
(200 mg PO 
within 1h prior 
to dilator 
placement) 
# of Dilapan-S 
Digoxin 
18 – 19w6d 
Yes 
Yes 
2-3 
By request 
20 – 21w6d 
Yes 
Yes 
3-4 
By request 
22 – 23w6d 
Yes 
Yes 
4-5 
Offered