The story of labour induction with a balloon serves as a cautionary tale
on several levels. Documented balloon labour induction dates to the mid
1800’s, though whether Barnes, Storer or Mattei was first in line is
disputed. Modern day use of the 30ml Foley catheter balloon for labour
induction with an unfavourable cervix was described in 1967 (Embrey MP
et al, BJOG 1967; 74:44-48). Around the same time, prostaglandin labour
induction was pioneered by Karim in Uganda, Embrey in Oxford, Bygdeman
in Stockholm and later Calder in Edinburgh (Calder A A et al, BJOG 1977;
84:264-8). The awkward Foley balloon was side-lined by all who could
afford the more elegant pharmacological alternative. Marketing may have
played a part.
In poorer settings, the 1990’s saw the prostaglandin analogue
misoprostol (the ‘People’s Prostaglandin’) usurping the place of the
Foley balloon (Hofmeyr GJ et al. BJOG 1999;106:798-803). We could at
last aspire to the prostaglandin ‘gold standard’ which had been
unaffordable for years. Of course, the reason misoprostol was affordable
was that it was not registered for labour induction. The costly,
systematic pre-registration evaluation of safety and dosage had been
skipped. A global pandemic of ruptured uteri raged until a safe-ish dose
was identified by clinical trial and error on a monumental scale.
Maternal deaths from uterine rupture have since been reduced, but not
eliminated.
Only after decades of flirtation with prostaglandins and their analogues
did evidence gradually emerge that something as devoid of elegance as a
cervical balloon was in fact safer than exogenous prostaglandins (Du YM
et al, BJOG 2017; 14:891-9) (figure 1), even safe enough for use in an
outpatient setting. The purpose-designed double balloon catheter has not
been found to be more effective than a standard 30ml Foley catheter
bulb.
Compared with vaginal prostaglandin E2, balloon labour induction reduces
the risk of uterine hyperstimulation and severe neonatal
morbidity/death. When in haste, adding a foley balloon to misoprostol
speeds up labour induction and reduces uterine hyperstimulation and
neonatal intensive care admission. Increased meconium passage with
prostaglandins versus balloon induction is usually assumed to be linked
to uterine hyperstimulation, but we have suggested that it may be a
direct prostaglandin effect on fetal bowel smooth muscle.
Having arrived at the beginning, we should not be surprised that
mechanical stimulation of endogenous prostaglandins proves to be safer
than pharmacological uterine stimulation.
Could balloon induction also be safer than amniotomy and oxytocin for
labour induction with a favourable cervix, particularly in higher-risk
situations such as previous caesarean section and potential fetal
compromise? A technical limitation with a favourable cervix is that a
standard Foley balloon may not be retained long enough for labour to be
triggered and progress without pharmacological stimulation. The
side-by-side Foley balloon technique (Hofmeyr GJ and Dalmacio R, BJOG
submitted for publication) may be a useful innovation to test in trials
to determine whether balloon labour induction has safety advantages for
women with favourable cervices as well.