Length of Cook Catheter Placement and Induction of Labor: a Randomized Controlled Trial
Phase: NA
Conditions: Induction of Labor
Sponsor: Brigham and Women's Hospital

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Length of Cook Catheter Placement and Induction of Labor 
    
 
 
NCT04233008 
 
Version date 2/21/18 
 
 

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Partners Human Research Committee Detailed Protocol 
 
Sarah Lassey, MD 
Sarah Little, MD (principal investigator) 
 
Study Title: Length of foley catheter placement and induction of labor: a randomized 
controlled trial 
 
Version date 2/21/18 
 
Background and Significance 
 
Induction of labor occurs in 24% of pregnancies in the United States (Hamilton). 
There are many maternal and fetal indications for induction of labor at various gestational 
ages of pregnancy. Induction of labor consists of initial cervical ripening followed by 
oxytocin. Cervical ripening helps the cervix soften, thin and dilate. There are multiple 
agents for cervical ripening including pharmacologic and mechanical dilation. 
Phamacologic agents include prostaglandins and oxytocin. Mechanical ripening most 
commonly refer to a foley catheter balloon device. Mechanical methods have been 
associated with lower rates of cesarean section compared with oxytocin alone (Boulvain). 
Previous studies have compared foley catheter placement for 12 vs. 24 hours and showed 
12 hours decreases time to delivery (Cromi). Recently, studies have looked at the efficacy 
of dual induction agents with combination of oxytocin and foley catheter with time to 
delivery (Levine).  
 
The cook catheter device, a type of foley catheter used for mechanical dilation, is 
a silicone double balloon catheter that can be inflated to 80mL/balloon. Per device 
guidelines it should not be left in place for more than 12 hours. Given these instructions 
the balloon is most often removed at 12 hours or spontaneously when it falls out given 
cervical dilation during the induction process.  
 
Currently there are no studies that evaluate the time to delivery in women with the 
foley catheter removed at 6 hours vs. 12 hours. Our theory is that the benefit of the foley 
catheter is within the first 6 hours and we will study whether there is faster time to 
delivery in this intervention group.  
This study has potential benefits for both individuals, hospital efficiency, and 
healthcare costs in the future. Longer inductions are associated with higher rates of 
postpartum hemorrhage and infection, therefore decreasing induction length would 
hopefully limit these labor complications. By decreasing the length of time for induction 
of labor, hospital and efficiency and healthcare costs would likely improve. Patients in 
the future would benefit from the knowledge gained in this trial if labor inductions are 
shorter with only 6 hours of a foley catheter placement and labor induction protocols 
change as a result.  
 
Specific Aims 
 
The objective of our study is to compare the time to delivery in women who 
undergo induction of labor with foley catheter and oxytocin for six vs. twelve hours. Our 

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hypothesis is women who undergo an induction with foley catheter for 6 hours will have 
a shorter time to delivery.  
 
Subject Selection 
 
Our study population will include women 18-50 years of age at term (37-41 6/7 
weeks) with a singleton gestation in cephalic presentation who are undergoing induction 
of labor. Both nulliparous and multiparous women will be included.  Women will need to 
have a bishop score <6 or cervical dilation  <2cm with intact membranes to be included, 
as these are the women currently being offered cervical ripening prior to labor induction. 
Women will be excluded if there is a contraindication to vaginal delivery. Women with 
history of a prior cesarean section will be excluded given their management may differ 
after removal of the foley catheter. Non-English speaking women will also be excluded 
given the length of time for induction on labor and delivery and inability to guarantee 24 
hour interpreter services. 
 
Women will be recruited from the Maternal Fetal Medicine and general Obstetrics 
clinics at Brigham and Women’s Hospital. They will be counseled in the office by their 
provider when an induction of labor is discussed, based on their cervical examination.  
 
Subject Enrollment 
 
Women will be enrolled from clinic prior to induction of labor based on their 
cervical exam and need for cervical ripening. Typically, inductions are scheduled in 
clinic within the week prior. When a patient is being scheduled for an induction, and it is 
deemed that they will need cervical ripening, they are potential candidates for this trial. 
The process of informed consent will happen in the clinic if the patient desires to 
participate in the study. The study staff and other selected physicians in clinic who have 
agreed to help with the study will consent the patient. Once consent is obtained, the 
subjects will then be randomized to either 6 vs. 12 hours with foley catheter. A random 
number generator will be used to randomize women in blocks of 10.  
 
If a woman is unsure about her desire to participate she will be able to go home 
from clinic with time to consider participation. If this is the case, she will be consented 
when she presents for her induction of labor by the study staff. 
 
Often times women at term are seen in clinic and the decision is made to proceed 
with induction on the same day. We propose that we are able to approach these women 
when they present to labor and delivery for induction. They will be given at least one 
hour to consider participation in the trial and to ask pertinent questions.   
 
Neither the patients nor the health care providers will be blinded to the assigned 
treatment group due to practical limitations.   
 
Study Procedures 
 
Upon presentation to labor and delivery the participant will have a foley catheter 
inserted digitally or by direct visualization with a speculum, as per provider preference as 
both methods are commonly used. The uterine component of the balloon will be inflated 
to maximum 60mL. The catheter will be taped to the inner thigh with gentle traction.  
Below is an image of cook catheter with both uterine and vaginal balloons 
inflated. In this study we will only inflate the uterine balloon (the distal balloon), 
following current standard practice on our labor and delivery unit.  

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In both groups participants will be started on a hospital-based oxytocin protocol. 
This protocol begins with 2 milliunits/min of oxytocin, increasing by 2 milliunits every 
15 minutes until regular uterine contractions occur. The maximum dose of oxytocin is 
considered to be 30 milliunits per our current protocol.  
 
The foley catheter will then be removed at 6 vs. 12 hours based on randomization. 
At that point health care providers will manage active labor per usual practice. Pitocin 
will be continued after foley removal, as is standard practice and health care providers 
many perform amniotomy at any point during the induction process with a 
recommendation for amniotomy when cervix more than 4cm dilated, consistent with 
literature demonstrating a shorter time to delivery with earlier amniotomy (Battarbee). 
Labor interventions are at the discretion of the healthcare provider. The participants will 
have continuous fetal monitoring throughout their induction, labor and delivery. The need 
for operative delivery or cesarean section will be at the discretion of the healthcare 
provider.  
 
Biostatistical Analysis 
 
The main outcome will be length of time to delivery. A subject’s participation 
will end with outcomes 4 weeks following delivery.  
 
Secondary maternal outcomes will be measured including cesarean delivery rate, 
time to active labor (>5cm dilated), delivery within 12 hours, delivery within 24 hours, 
maternal length of stay, and indication for cesarean delivery. We will also calculate a 
composite maternal morbidity outcome including estimated blood loss, higher-order 
laceration, blood transfusion, endometritis, wound infection, venous thromboembolism, 
hysterectomy, ICU admission or death. These outcomes will also be stratified by parity. 
We will also evaluate rates of analgesia in both groups.  
 
A composite neonatal morbidity will be calculated including culture-proven 
neonatal sepsis, neonatal blood transfusion, hypoxic-ischemic encephalopathy, 
intraventricular hemorrhage grade 3 or 4, or therapeutic hypothermia. We will also 
analyze NICU admission, NICU admission for greater than 48 hours, and neonatal length 
of stay.  
 
In the literature, the mean time to delivery with an induction of labor in 18 hours. 
A four hour reduction in time to delivery is considered clinically meaningful and has 
been used in prior studies evaluating induction of labor (Levine). A Type I α error of 0.05 

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was selected. Assuming 80% power and a two-sided P value we would need 71 
participants in each group for total sample size 142. However, given that some patients 
will undergo cesarean section during their induction of labor, we will exclude cesarean 
section in a sensitivity analysis. Assuming that 20% of patients will have a cesarean 
section, we will include 89 women in each arm, 178 women total.  For statistical 
purposes, intent to treat analysis will be performed. Non-parametric measures will be 
used for statistical analysis. These models will also be adjusted for parity. 
 
Risks and Discomforts 
 
Women may experience discomfort with foley catheter insertion, which will be 
handled with pain medication in a similar way to current practices on labor and delivery.  
 
Because the foley catheter is routinely used for cervical ripening during labor 
induction on labor and delivery we think that there is minimal increased risk from the 
study. However, by limiting the foley catheter to 6 hours, the length of time of cervical 
ripening is limited. Upon removal of the catheter at 6 hours the cervix may not be ripened 
and therefore increase the risk of prolonged induction and ultimately cesarean section.  If 
the intervention group is associated with longer length of time to delivery it may also be 
associated with increased blood loss and risk of infection, which are known risks of 
prolonged induction. Our study, however, allows physicians to manage labor as deemed 
appropriate after foley removal. Thus, if cervical ripening is felt to be inadequate, 
alternative cervical ripening agents (such as misoprostol) could still be used in 
appropriate candidates. Moreover, we feel it is most likely that the 12-hour foley group 
(the current standard of care) will have longer labor inductions, not the 6-hour 
experimental group, consistent with prior studies showing that labors were longer with 24 
hour foley placement rather than 12 hour placement (Cromi). Also, our clinical 
experience is that when foley balloons are actively managed (i.e. the patient is checked 
vaginally sooner than 12 hours and tension is applied to see if the foley is ready to come 
out) most women achieve adequate cervical dilation much sooner than the maximum of 
12 hours.  
 
Potential Benefits 
Because this study is a randomized controlled trial, there is no direct benefit to 
individuals. Given the nature of the study we do not know if, and which treatment is 
better. Furthermore, the study is randomly allocated so there is an equal chance of the 
patient being in either treatment arm. 
There are however many benefits for the healthcare system in the future. By 
determining the faster method for induction of labor we may find that risk of infection 
and blood loss are lessened. The fetus also benefits by shorter induction times by limiting 
the time of intrauterine stress during labor and delivery. Healthcare cost would benefit 
from the information gained in this study by decreasing hospital stays. Currently, the 
most effective method of inducing labor remains unknown. 
 
Monitoring and Quality Assurance 
 
The principal investigator will review the entries for each participant to ensure 
they are complete. We will not perform any interim analysis, as we feel there is minimal 
risk from the study protocol and would not stop the study early. When adverse events 

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occur they will be reported to the Partners’ IRB within 5 days with a detailed description 
of the event as described in the guidelines for adverse events reporting. Serious adverse 
events (severe hemorrhage, maternal death, neonatal death, neonatal hypoxemic 
encephalopathy) will be reviewed by the head of labor and delivery and the study staff to 
ensure the outcome is not related to the study protocol.  
 
References 
Battarbee AN, Palatnik A, Peress DA, et al. Association of early amniotomy after foley 
balloon catheter ripening and duration of nulliparous labor induction. Obstetrics and 
Gynecology 2016; 128(3): 592-7.  
 
Boulvain M, Kelly A, Lohse C, Stan C, Irion O. Mechanical methods for induction of 
labour. Cochrane Database of Systematic Reviews 2001, Issue 4. Art. No.: CD001233.  
Cromi A, Ghezzi F, Agosti M, et al. Is transcervical Foley catheter actually slower than 
prostaglandins in ripening the cervix? A randomized study. American Journal Obstetrics 
and Gynecology 2011; 204(4):338.e1-7. 
Hamilton BE, Martin JA, Osterman MJK, et al. Births: final data for 2014. National Vital 
Statistics Reports 2014; 64(12): 1-65.  
 
Levine LD, Downes KL, Elovitz MA, et al. Mechanical and pharmacologic methods of 
labor induction: a randomized controlled trial. Obstetrics and Gynecology 2016; 128(6): 
1357-1365.