1
2
3
4
5
6
7
8
9
10
1
2
3
4
5
6
7
8
9
20
1
2
3
4
5
6
7
8
9
30
1
2
3
4
5
6
7
8
9
40
41
 
Preparing for induction
of labor
1 Introduction
2 Assessing the cervix
3 Prostaglandins for cervical ripening
3.1 Oral prostaglandins
3.2 Vaginal prostaglandins
3.3 Endocervical prostaglandins
3.4 Extra-amniotic prostaglandins
3.5 Direct comparisons between different routes
4 Other methods for cervical ripening
4.1 Estrogens
4.2 Oxytocin
4.3 Mechanical methods
4.4 Relaxin
4.5 Breast stimulation
5 Prostaglandins versus other methods
6 Hazards of cervical ripening
7 Conclusions
1 Introduction
The decision to bring pregnancy to an end before the spontaneous
onset of labor is one of the most drastic ways of intervening in the
natural process of pregnancy and childbirth. The reasons given for elective delivery (which may be achieved either by inducing labor or by
elective cesarean section) range from the life-saving to the trivial. There
has been very little methodologically sound research on the indications
for elective delivery; most of the research has been concerned with the
methods to achieve it. Although comparisons of these methods are
secondary to the more fundamental question of when or whether an
elective delivery is required, once the decision for an elective delivery
is made, the method chosen becomes important.
SOURCE: Murray Enkin, Marc J.N.C. Keirse, James Neilson, Caroline Crowther, Lelia Duley, Ellen Hodnett, and
Justus Hofmeyr. A Guide to Effective Care in Pregnancy and Childbirth, 3rd ed. Oxford, UK: Oxford University
Press, 2000.
DOWNLOAD SOURCE: Maternity Wise™ website at www.maternitywise.org/prof/
© Oxford University Press 2000

1
2
3
4
5
6
7
8
9
10
1
2
3
4
5
6
7
8
9
20
1
2
3
4
5
6
7
8
9
30
1
2
3
4
5
6
7
8
9
40
41
    
2 Assessing the cervix
The state of the cervix at the time of induction is one of the most
important determinants of the subsequent course of events. An
‘unripe’ cervix (one which is not ready for induction of labor) fails to
dilate adequately in response to uterine contractions. Attempted
induction when the cervix is not ripe may result in high rates of induction failure, protracted and exhausting labors, a high cesarean-section
rate, and other complications, such as intra-uterine infection when
amniotomy is employed, as well as uterine hypertonus and other
complications with the use of oxytocics.
Assessment of the state of the cervix is highly subjective and even
experienced examiners may differ in their appraisal of cervical features.
Several scoring systems have been developed in attempts to establish
more comparable guidelines for cervical assessment. The best known
of these is the score proposed by Bishop, which rates five different qualities: effacement, dilatation, and consistency of the cervix; position of
the cervix relative to the axis of the pelvis; and descent of the fetal
presenting part. Most other scoring systems use the same components,
although with different weighting. There is some evidence that cervical
dilatation alone is more predictive of subsequent progress than the
composite score
As there is considerable overlap between the processes of cervical
ripening and labor induction, this chapter should be read in conjunction with chapter 40 (methods of inducing labor).
3 Prostaglandins for cervical ripening
Doses of prostaglandins, which by themselves are insufficient to induce
labor successfully, produce a marked softening of the uterine cervix.
This softening results more from an effect on the cervical connective
tissue than from uterine contractions.
Prostaglandins can effectively ripen the cervix and facilitate induction of labor. Labor commences before the start of induction (during
the period allocated for cervical ripening) more often in women
receiving prostaglandins for cervical ripening than in women who
receive placebo or no specific treatment. Prostaglandin-ripening of the
cervix increases the likelihood of a successful induction of labor, and
of achieving vaginal birth within 12 or 24 hours.
The effect of prostaglandin-ripening on the pain experienced
during labor is not clear. The few reports that provide data on the use
   
1
2
3
4
5
6
7
8
9
10
1
2
3
4
5
6
7
8
9
20
1
2
3
4
5
6
7
8
9
30
1
2
3
4
5
6
7
8
9
40
41

of pharmacological or epidural analgesia show that epidural analgesia
is less frequently used among prostaglandin-treated women than
among women in the control groups, which at least suggests that these
women may experience less pain.
‘Uterine hypertonus’ or ‘uterine hyperstimulation’ (excessive uterine
contractility), either during the period of cervical ripening or during
the subsequent induction of labor, occurs more often in prostaglandintreated women than among women who receive placebo or no treatment prior to induction. Whether for this or for other reasons, fetal
heart-rate abnormalities also tend to occur more frequently with
prostaglandin treatment. Neither of these trends lead to an increased
incidence of operative delivery. On the contrary, prostaglandin treatment reduces the rate of operative delivery with a modest but statistically significant decrease in the cesarean-section rate and a more
marked decrease in the rate of instrumental vaginal delivery.
Few trials provide data on the incidence of postpartum hemorrhage
and/or the use of blood transfusion. The available data do not suggest
that these outcomes are influenced by the use of prostaglandins for
cervical ripening, but the estimates are not precise.
None of the data available suggest any influence, good or bad, of
cervical ripening on neonatal outcomes. There is a trend towards
fewer low Apgar scores in babies born to mothers who received
prostaglandins but few trials provide data on more substantive infant
outcome measures, such as resuscitation of the newborn, admission to
a special care nursery, and perinatal death.
3.1 Oral prostaglandins
Oral prostaglandin E2 has been shown to be little or no better than
either placebo or no treatment for cervical ripening. The synthetic
prostaglandin E1 analog misoprostol, administered orally, appears to
be effective both for cervical ripening and induction of labor but there
are inadequate data on its safety (see Chapter 40).
3.2 Vaginal prostaglandins
Vaginal administration of prostaglandins for cervical ripening has been
studied more extensively than oral administration. The results show
an increase in the frequency of labor onset during the ripening period,
a decrease in the incidence of failed induction, and an increase in the
likelihood of ‘hypertonus’ or ‘hyperstimulation’. The rate of both
instrumental vaginal delivery and cesarean section is decreased with
the use of vaginal prostaglandins. No effect has been demonstrated on
any infant outcomes.

1
2
3
4
5
6
7
8
9
10
1
2
3
4
5
6
7
8
9
20
1
2
3
4
5
6
7
8
9
30
1
2
3
4
5
6
7
8
9
40
41
    
Women receiving vaginal prostaglandins for cervical ripening are
more likely to undergo cesarean section during the time interval
allowed for cervical ripening than women receiving the control treatment. This higher incidence of cesarean section during cervical ripening is more than compensated for by a lower cesarean-section rate
during induced labor.
Of the many preparations used for vaginal administration, the
modern gel and pessary preparations are more effective than the tablet
forms previously used. Vaginal administration of misoprostol is
discussed in Chapter 40.
3.3 Endocervical prostaglandins
Evaluations of prostaglandins administered in a viscous gel in the
cervical canal have been conducted mostly with 0.5 mg PGE2, a dose
that is much smaller than is used with either the oral or vaginal routes
of administration. Endocervical prostaglandin administration is
more likely than either placebo or no treatment to result in uterine
activity, in the onset of labor, in a reduction of the need for formal
induction of labor at the end of the ripening period, and in delivery
during the ripening period. As with vaginal prostaglandins, more
women undergo cesarean section during the ripening period, but this
is again compensated for by a reduction in the rate of cesarean during
labor. The likelihood of failed induction is reduced, as is the rate of
operative delivery.
3.4 Extra-amniotic prostaglandins
Few placebo-controlled trials have evaluated extra-amniotic administration of a prostaglandin for cervical ripening. The few data available
do not permit adequate judgement about the relative merits or hazards
of this specific route of administration.
3.5 Direct comparisons between different routes
Controlled comparisons of endocervical with vaginal PGE2 gel for
cervical ripening suggest that the endocervical approach results in
more women going into labor or delivering during ripening (if this is
considered to be a desirable outcome). No statistically significant
differences are found in any other outcomes. The choice between these
approaches may be best determined by clinical preference.
Labor is more likely to occur during ripening with the use of extraamniotic rather than vaginal or endocervical prostaglandins. No differential effects on other outcome measures have been found in the few
    
1
2
3
4
5
6
7
8
9
10
1
2
3
4
5
6
7
8
9
20
1
2
3
4
5
6
7
8
9
30
1
2
3
4
5
6
7
8
9
40
41

controlled trials that have been conducted, but the trials were too small
to detect modest differences.
4 Other methods for cervical ripening
4.1 Estrogens
The use of estrogens for cervical ripening has been suggested on the
theoretical grounds that these agents might ripen the cervix without
concomitant effects on uterine contractility. Data from controlled trials
with a variety of estrogenic preparations, failed to show any beneficial
effects.
4.2 Oxytocin
Oxytocin infusions for prolonged periods of time (as is usually the case
when the aim is to ripen the cervix) are unpleasant, limit the woman’s
mobility, and may lead to water intoxication when administered in
large doses. Oxytocin administration to ripen the cervix (rather than
to induce labor) serves no useful purpose and should be abandoned.
4.3 Mechanical methods
Mechanical devices, such as catheters with or without extra-amniotic
saline infusion, laminaria tents, and synthetic hydrophylic materials,
have been shown to increase cervical ripeness scores and may increase
the proportion of women going into labor. No effect has been shown on
the incidence of operative delivery, puerperal fever, or low Apgar scores.
Several recent trials have shown little difference, if any, in effects
between various mechanical methods and prostaglandins administered
vaginally or intracervically, but all of these trials have been small.
Factors to be taken into account when choosing a method of cervical
ripening are, on the one hand, that mechanical methods are more
uncomfortable to apply, while on the other hand, they are less
expensive and less likely to cause uterine hyperstimulation than
prostaglandins.
4.4 Relaxin
The use of porcine relaxin to soften the cervix and shorten labor had
a brief vogue of popularity in the 1950s. Placebo-controlled trials failed
to show any benefit.
Recent trials with a purer preparation and recombinant human
relaxin have also failed to demonstrate any useful effects. Relaxin

1
2
3
4
5
6
7
8
9
10
1
2
3
4
5
6
7
8
9
20
1
2
3
4
5
6
7
8
9
30
1
2
3
4
5
6
7
8
9
40
41
    
should not be adopted into clinical practice unless large, properly
controlled trials show evidence of benefit.
4.5 Breast stimulation
In an attempt to explore ‘natural’ methods for ripening the cervix, two
groups of investigators have evaluated the effects of breast stimulation.
Both reported that women allocated to breast stimulation were more
likely to go into labor during the intervention period than those allocated to the control group, but there was no suggestion as to whether
this resulted in easier labor or delivery.
5 Prostaglandins versus other methods
A number of small trials have compared prostaglandins with alternative agents for cervical ripening, including oxytocin and estrogens.
None of these trials were large enough to provide useful estimates of
effect, either individually or by combining their data. The general
conclusion derived from these studies suggests that prostaglandins are
more effective than the other agents.
6 Hazards of cervical ripening
Increasing the readiness of the cervix for induction is not a trivial
intervention. Depending on the method used, the risks of the ripening include a (small) danger of intra-uterine infection with mechanical procedures and extra-amniotic drug administration, an increased
likelihood of uterine hypertonus and fetal heart-rate abnormalities,
and a certain amount of discomfort and inconvenience for the
mother. Some of these hazards, uterine hypertonus and fetal heart-rate
abnormalities in particular, are ill-defined and of unclear significance
but they have sometimes prompted cesarean sections during cervical
ripening.
The risks of cervical ripening are not limited to those related to
the intervention itself but include those associated with induction of
labor. The greatest hazard is that the ease of cervical ripening may
result in unnecessary induction of labor in women for whom an
artificial ending of pregnancy would not otherwise have been contemplated.

1
2
3
4
5
6
7
8
9
10
1
2
3
4
5
6
7
8
9
20
1
2
3
4
5
6
7
8
9
30
1
2
3
4
5
6
7
8
9
40
41

7 Conclusions
No attempts should be made to ripen the cervix, unless there are valid
grounds for ending pregnancy artificially. None of the successful
methods of cervical ripening act exclusively on the cervix and all of
them tend to increase myometrial contractility.
When it is necessary to induce labor in the presence of an ‘unripe’
cervix, the method used should not only increase cervical readiness,
but must also increase the likelihood of spontaneous vaginal birth of
a healthy baby within a reasonable period of time and involve minimal
inconvenience or discomfort for the mother.
Use of prostaglandins decreases the likelihood of ‘failed induction’,
decreases the incidence of prolonged labor, and increases the chances
of a spontaneous vaginal birth. There are still insufficient data to allow
any confident conclusions about the effects on the baby.
Oral administration of prostaglandins, other than misoprostol, has
no value for ripening the cervix. Extra-amniotic administration, if used
at all, should be reserved for women with very ‘unripe’ cervices and
for those who are unlikely to respond adequately to vaginal or endocervical administration.
Vaginal and endocervical administration of prostaglandin PGE2 in
gel or pessary form are the current methods of choice. The two forms
of administration seem equally effective. The vaginal route has the
advantage of ease of application.
Recent reports have demonstrated the effectiveness of mechanical
methods, particularly those employing a catheter balloon, though the
discomfort caused by insertion may limit the acceptability of these
methods.
Sources
Effective care in pregnancy and childbirth
Chalmers, I. and Keirse, M.J.N.C., Evaluating elective delivery.
Keirse, M.J.N.C. and van Oppen, A.C., Preparing the cervix for induction of labour.
Cochrane Library
Alfirevic, Z., Howarth, G. and Gausmann, A., Oral misoprostol for
induction of labour with a viable fetus.

1
2
3
4
5
6
7
8
9
10
1
2
3
4
5
6
7
8
9
20
1
2
3
4
5
6
7
8
9
30
1
2
3
4
5
6
7
8
9
40
41
    
Boulvain, M. and Irion, O., Stripping/sweeping the membranes for
inducing labour or preventing post-term pregnancy.
Boulvain, M., Irion, O., Lohse, C. and Matonhodze, B., Mechanical
methods for inducing labour [protocol].
Hofmeyr, G.J. and Gulmezoglu, A.M., Vaginal misoprostol for cervical
ripening and labour induction in late pregnancy.
Lumbiganon, P., Laopaiboon, M., Kuchaisit, C. and Chinsuwan, A.,
Oral prostaglandins (excluding misoprostol) for cervical ripening
and labour induction when the baby is alive [protocol].
Turnbull, D.A., Wilkinson, C.S. and Griffiths, E., Breast stimulation
for cervical ripening in pregnancy [protocol].
Other sources
Brennand, J.E., Calder, A.A., Leitch, C.R., Greer, I.A., Chou, M.M. and
MacKenzie, I.Z. (1997). Recombinant human relaxin as a cervical
ripening agent. Br. J. Obstet. Gynaecol., 104, 775–80.
Gilson, G.J., Russell, D.J., Izquierdo, L.A., Qualls, C.R. and Curet, L.B.
(1996). A prospective randomized evaluation of a hygroscopic
cervical dilator, Dilapan, in the preinduction ripening of patients
undergoing induction of labor. Am. J. Obstet. Gynecol., 175, 145–9.
Keirse, M.J.N.C. and de Koning Gans, H.J. (1995). Randomized
comparison of the effects of endocervical and vaginal prostaglandin
E2 gel in women with various degrees of cervical ripeness. Dutch
Collaborative Prostaglandin Trialists’ Group. Am. J. Obstet.
Gynecol., 173, 1859–64.
Stempel, J.E., Prins, R.P. and Dean, S. (1997). Preinduction cervical
ripening: a randomized prospective comparison of the efficacy and
safety of intravaginal and intracervical prostaglandin E2 gel. Am. J.
Obstet. Gynecol., 176, 1305–9.
St. Onge, R.D. and Connors, G.T. (1995). Preinduction cervical
ripening: a comparison of intracervical prostaglandin E2 gel versus
the Foley catheter. Am. J. Obstet. Gynecol., 172, 687–90.
Williams, M.C., Krammer, J. and O’Brien, W.F. (1997). The value of
the cervical score in predicting successful outcome of labor induction. Obstet. Gynecol., 90, 784–9.