Foley catheter for Induction of Labour filled with 30ml or 60ml

Induction of labour is an intervention designed to artificially initiate
uterine contractions leading to progressive dilatation and effacement of the
cervix and birth of the baby. Induction of labour is a common, if not the most
common, obstetrical procedure: twenty-two percent of all deliveries in the
Netherlands in 2007 were induced. Compared to the spontaneous onset of labour,
induction of labour is associated with prolonged labour, more instrumental
deliveries and a higher rate of caesarean sections, especially when the cervix
is unfavourable.

A recent Dutch survey showed a wide variety of methods in use for induction of
labour, with intravaginal prostaglandin gel used most frequent. [Reijers 2009]
A less frequently used method of cervical ripening is the transcervical Foley
catheter. Another recent Dutch randomised controlled trial reported a similar
success-rate of induction of labour when compared with intravaginal
prostaglandins with fewer maternal and neonatal side-effects. In that study,
the Foley catheter was filled with 30mL of sterile saline. [Jozwiak 2011]

Embrey and Mollison first used a Foley catheter filled with 50mL for cervical
ripening in 1967. [Embrey 1967] Since then, various volumes of insufflation
were reported. Most studies used 30mL of saline to fill the balloon because it
was thought that more volume would only increase the balloon diameter minimally
and thus would not promote additional cervical dilatation. However, others
thought that insufflating the balloon up to 80mL would increase cervical
dilatation and more endogenous prostaglandin secretion.

When directly comparing different insufflation volumes, several studies have
reported similar succes rates when the balloon catheter is filled with either
60mL or 80mL compared with 30mL with more deliveries within 24 hours of Foley
catheter placement [Levy 2004, Kashanian 2009] and within 12 hours of placement
[Delaney 2010] with the larger insufflation volumes. When oxytocin was started
after expulsion of the catheter, Levy et al found that the larger inflation
size was significantly associated with a higher rate of postripening dilatation
of 3cm or more (76% compared with 52%) and, in primiparous, it resulted in a
higher rate of deliveries within 24 hours (71% compared with 49%) as well as a
decreased need for oxytocin augmentation (69% compared with 905). When
comparing a 80mL with a 30mL Foley catheter, the number of favorable Bishop
scores, change in Bishop score and overall vaginal delivery rate were all
significantly better in the 80mL group as compared with the 30mL
group.[Kashanian 2009]

Approximately 50% of the women in both groups in the study by Delaney et al.
had received some form prostaglandin prior to Foley catheter placement and
intravenous oxytocin infusion was started within 30 minutes of Foley catheter
placement. Levy et al. removed the Foley catheter 12 hours after placement,
after which oxytocin augmentation was started, (regardless of dilatation) and
only performed artificial rupture of membranes when the woman had at least 3
painful contractions per hour and when cervical dilatation exceeded 3cm. In the
study by Kashanian et al., the Foley catheter was removed 6 hours after
placement, after which oxytocin augmentation was started, regardless of
dilatation. Also, a 500mL weight was attached to the end of the catheter.

The methodological aspects of these studies do not reflect the Dutch national
guideline for induction of labour which recommends cervical priming in case of
an unfavourable cervix, followed by artificial rupture of membranes once the
cervix has been judged to be favourable. Augmentin of labour using oxytocin may
be started in case of insufficient contractions. [NVOG Richtlijn Inductie 2006]
Traction on the catheter has reported not to be of influence on the succes rate
of induction of labour and may be unnecessarily painful and may inhibit free
ambulation during this stage of labour.

A shorter time from induction to delivery due to a larger Foley catheter
balloon inflation may lead to a decrease in the duration of labour, maternal
exhaustion and hospitalization costs, without increased caesarean delivery
rates and maintaining both neonatal and maternal safety.

Primary objective: To assess in term pregnant women with an unfavourable cervix
(Bishop score < 6, Appendix1) the time interval between induction of labour and
birth with a transcervical Foley catheter filled with 30mL compared to
induction of labour with a transcervical Foley catheter filled with 60mL.

Secondary objectives: To study maternal and neonatal morbidity, to study the
costs of both methods.

Non-blinded Open-label Randomised Controlled Clinical Trial will be held in a
hospital setting starting in the spring of 2013 lasting until all necessary
inclusions are met.

Transcervical Foley catheter filled with 30mL or a transcervical Foley catheter
filled with 60mL.

In this study the same method of induction (Foley catheter) with a different
volume will be compared. No experimental medication will be used. No additional
physical examination is needed for this study, nor will extra blood be taken
from the subjects. One vaginal swab will be taken at moment of catheter
insertion. No additional risks or burden are expected from the study. A
questionnaire will have to be filled in after insertion of the catheter, asking
about painscores, physical discomfort and urination problems.