Background and Rationale:
Induction of Labor (IOL) is one of the most common interventions in obstetrics. IOL is
performed due to fetal, maternal or pregnancy complications to reduce the risk of
complication. IOL methods will depend of the state of the cervix at the beginning of the
procedure. If cervix is considered unfavorable (Bishop score ≤ 5) an initial phase of
ripening is usually proposed. There are various methods of cervical ripening, which can
be divided into non-pharmacological (e.g., mechanical methods with transcervical Foley
catheter or Cook balloon) and pharmacological (e.g., prostaglandins). IOL can be a
long-lasting procedure, especially when cervical ripening is necessary.
Two recent, small studies have shown that the use of warm fluid to inflate the balloon
catheter (BC) inserted through the cervix reduces the time of cervical ripening, hence
potentially reducing the time of IOL. These results are the only data available regarding
the use of saline at different temperatures for inflating the balloon in mechanical
methods and show promising effects in terms of reduction in the length of the cervical
ripening and labor.
The cervix is mainly composed of collagen. Studies show that the use of heat on
connective tissue increase the potential elongation of collagen tissue and the
denaturation of this protein.
We hypothesize that the use of heat in the cervical ripening can accelerate the
denaturation of the collagen and accelerate the softening of the cervix and therefore
reduce the duration of cervical ripening and labor.
Objective(s):
The primary objective of the study is to determine if the use of heated saline in the BC
used for cervical ripening reduces the length of BC duration, defined as the time from
the insertion to the expulsion or artificial removal of the BC.
The secondary objectives are to evaluate if the use of heated saline compared with room
temperature:
Decreases the length from the start of the induction until the achievement of a
favorable cervix (Bishop score >5).
Decreases the length from the start of the induction until full dilation
Decreases the length from the start of the induction until delivery
Increases the rate and the speed of spontaneous rupture of membranes (ROM) during
cervical ripening
Impacts on the rate of cesarean delivery.
Impacts on the pain and the satisfaction in women undergoing cervical ripening
Impacts on obstetrical and neonatal complications
Study Design:
Prospective, single-center, randomized, two-arm, controlled trial, including women
requiring cervical ripening during the process IOL using Balloon catheter
Number of Participants with Rationale:
A total of 290 women will be recruited (145 women in each group) in order to show a
reduction in the duration of BC placement, considering a significance criterion set to
0.05 (alpha, two- tailed), and an expected power of at least 90%.
Study procedures:
Patients will be allocated in one of this two groups:
In both groups, the insertion of the BC will be done following the same procedure:
The operator will introduce a 14Fr or 18Fr Balloon catheter through the cervical canal,
up above the internal orifice using a long Pean clamp and inflate the internal balloon
with 30 to 80ml of saline water (NaCl 0.9%) -either heated or unheated, depending on the
allocation group- according to the mechanic resistance with a graduated syringe.
Statistical Considerations Main analysis will be performed on an intention-to-treat
basis. The main outcome will be evaluated by plotting survival functions according to the
allocation group, using the Kaplan-Meier estimator. The associations will be considered
as statistically significant when the p-value is below 0.05 (probability of type I error
= 0.05). This analysis is also planned for objectives 2 (interval from beginning of IOL
and achievement of a favorable cervix) and 3 (interval from beginning of IOL and
delivery). For the other outcomes, comparison will be performed using Fisher's exact
test, Student's t-test or the Mann-Whitney U test, according to the type of variable.
