Does induction of labour increase the risk ofcaesarean section? A systematic review andmeta-analysis of trials in women with intactmembranesS Wood,a,b S Cooper,a S Rossa,b

a Departments of Obstetrics and Gynaecology, University of Calgary, Calgary, AB, Canada b Community Health Sciences, University of

Calgary, Calgary, AB, Canada

Correspondence: Dr S Wood, Department of Obstetrics and Gynaecology, University of Calgary, 4th Floor, North Tower, Foothills Medical

Centre, 1441 – 29th Street NW, Calgary, AB, T2N 4J8, Canada. Email Stephen.wood@albertahealthservices.ca

Accepted 8 February 2013. Published Online 3 July 2013.

Background Recent literature on the effect of induction of labour

(compared with expectant management) has provided conflicting

results. Reviews of observational studies generally report an

increase in the rate of caesarean section, whereas reviews of

post-dates and term prelabour rupture of membrane (PROM

trials suggest either no difference or a reduction in risk.

Objective To evaluate with a systematic review and meta-analysis

of randomised controlled trials (RCTs) whether or not the

induction of labour increases the risk of caesarean section in

women with intact membranes.

Search strategy Literature search using electronic databases:

MEDLINE, EMBASE, and the Cochrane Database of Clinical

Trials.

Selection criteria RCTs comparing a policy of induction of labour

with expectant management in women with intact membranes.

Data collection and analysis A total of 37 trials were identified

and reviewed. Quantitative analyses with fixed- and

random-effects models were performed with REVMAN 5.1.

Main results Of the 37 RCTs, 27 were trials of uncomplicated

pregnancies at 37–42 weeks of gestation. The remaining ten

evaluated induction versus expectant management in pregnancies

with suspected macrosomia (two), diabetes in pregnancy (one),

oligohydramnios (one), twins (two), intrauterine growth

restriction (IUGR) (two), mild pregnancy-induced hypertension

(PIH) (one), and women with a high-risk score for caesarean

section (one). Meta-analysis of 31 trials determined that a policy

of induction was associated with a reduction in the risk of

caesarean section compared with expectant management (OR

0.83, 95% CI 0.76–0.92).

Author’s Conclusions Induction of labour in women with intact

membranes reduces the risk of caesarean section. Review of the

trials suggests that this effect may arise from non-treatment

effects, and that additional trials are needed.

Keywords Caesarean section, clinical trials, induction of labour,

meta-analysis.

Please cite this Paper as: Wood S, Cooper S, Ross S. Does induction of labour increase the risk of caesarean section? A systematic review and meta-analysis

of trials in women with intact membranes. BJOG 2014;121:674–685.

Introduction

Rising caesarean delivery rates in North America and Eur-

ope continue to be a major concern for health policy

experts, administrators, and medical professional associa-

tions.1,2 A number of factors have been implicated, such as

the decline in rates of trial of labour after caesarean section,

and increasing rates of obesity, late maternal age, and

induced labour.1,3,4 Reducing the frequency of induction is

often cited as an approach to reversing the trend in caesar-

ean section rates.5 The association between induction of

labour and caesarean delivery is largely based on the find-

ings of observational studies.6–11 One clear limitation of

the observational literature is that induction is often indi-

cated by complications of pregnancy, which may indepen-

dently increase the risk of caesarean section. Additionally,

some authors have found that using survival analysis and

comparing the outcomes of women induced with those

who deliver at later gestational ages eliminates the effect of

induction12; however, this has not been a consistent find-

674 ª 2013 RCOG

DOI: 10.1111/1471-0528.12328

www.bjog.orgSystematic review

ing.13 Therefore, a clearer picture may emerge from clinical

trials where women with a specific pregnancy complication

are randomised to a policy of induction of labour versus

further expectant management. In the setting of prelabour

rupture of membranes (PROM) at term, large clinical tri-

als, as well as meta-analysis, have clearly established that a

policy of induction does not increase the risk of caesarean

section.14 Additionally, with induction for PROM, the risk

of caesarean section appears to be low,15 perhaps indicating

the relative state of cervical maturation, or that the labour

process has already begun.16 A 2006 Cochrane review of

trials of induction for post-term pregnancy concluded that

there was no difference in the risk of caesarean section

between induction and expectant management.17 Caughey

and colleagues.18 reviewed both observational studies and

clinical trials of ‘elective’ induction. They found the obser-

vational studies consistently documented a lower rate of

caesarean section in women having spontaneous versus

induced labour. In contrast, meta-analysis of eight clinical

trials, six of which were post-dates trials, concluded that

caesarean section was reduced by induction. Of note, the

authors excluded all non-English articles.

Our goal was to evaluate whether induction of labour,

compared with a policy of expectant management, in

women with intact membranes increased the rate of caesar-

ean section. To that end, we undertook a systematic review

and meta-analysis.

Methods

We systematically searched Ovid MEDLINE (1950–2012,week 23, 2010) and EMBASE (1980–2012, week 23). The

MEDLINE search for labour induction included the Medi-

cal Subject Headings (MeSH) term ‘labour, induced’ and

the keywords ‘induced labour’, ‘induction of labour’, and

‘labour induced’. EMBASE followed a similar strategy with

the MeSH term ‘labour induction’ and keywords ‘labour

induced’, ‘induction of labour’, and ‘induced labour’. All

results were then limited to ‘clinical trial’. A review of the

Cochrane Database of Clinical Trials was also performed.

All citations were then independently reviewed by two of

the authors, S.W. and S.C. Titles and abstracts were

reviewed and full texts were obtained for all articles that

the reviewers felt were relevant, or also if they were uncer-

tain of their relevance. The references of these studies were

also searched for additional articles. Studies were included

if a policy of induction of labour, for indications other

than preterm rupture of membranes (PROM), was com-

pared with expectant management and outcome data on

route of delivery were provided. All three of the authors

independently assessed studies for potential selection, per-

formance, and attrition bias, as recommended for assessing

the quality of clinical trials in meta-analysis.19 The compli-

ance with allocated treatment, as well as the degree of

crossover, were also assessed.

All studies were graded as high or low quality based on

three key quality indicators: adequate randomisation and

allocation concealment; limited losses to follow-up (<20%);

and intention-to-treat analysis.18 Studies that were deficient

in any of these areas were graded as low quality. Studies

were not included in the quantitative summary analysis,

unless intention-to-treat analysis was presented or could be

calculated from the available data. Quantitative analyses

with fixed- and random-effects models were performed

with REVMAN 5.1 (The Nordic Center, The Cochrane Colla-

boration, Copenhagen). Statistical assessment for heteroge-

neity was performed and considered statistically significant

if P < 0.05. A subgroup analysis limited to high-quality tri-

als was planned a priori.

Results

The literature search identified 2794 citations. A review of

the abstracts determined that there were 1368 unique cita-

tions. Details of the study selection are outlined in

Figure 1. Review of the abstracts identified 42 possible tri-

als for which the full articles were reviewed by all of the

authors. Three of the publications were not in English: one

was in German,20 one was in French,21 and one was in

Spanish22. These were reviewed with the assistance of two

obstetrician-gynaecologists and an Internal Medicine-OB

specialist at the authors’ institution. Five of the trials were

determined to be cervical ripening trials and were excluded.

A citation search identified two additional papers. One of

these, an abstract,23 did not clearly report the frequency of

caesarean section in the two study groups, and was there-

fore excluded. The other was a conference abstract that did

supply sufficient data to be included.24 Another article was

included as the trial protocol had been identified in our lit-

erature search,25 and the publication of the final results was

later identified.26 Therefore, a total of 38 trials were

included in the review. Further review identified that one

of the trials was a duplicate publication of a previously

published German article20,27; therefore, only the English

version was included in the review. One trial, which rando-

mised women with twins to early term delivery versus stan-

dard care included women who planned to have a

caesarean section. The primary author of the article was

contacted and the details of the outcomes of the planned

vaginal delivery groups were kindly provided.

Of the remaining 37 studies, 27 were induction trials of

uncomplicated pregnancies at 37–42 weeks of gesta-

tion.21,22,27–51 The remaining ten studies evaluated induc-

tion versus expectant management in pregnancies with

suspected macrosomia,24,52 diabetes in pregnancy,53 oligo-

hydramnios,54 twins,26,55 intrauterine growth restriction

ª 2013 RCOG 675

Induction of labour and caesarean section

(IUGR),56,57 mild pregnancy-induced hypertension (PIH),58

and women with a high-risk score for caesarean section.59

The characteristics of the 37 trials are outlined in

Table 1(and are further detailed in Table S1). The methods

of induction were not identical in all studies. The early

investigations generally used artificial rupture of mem-

branes with oxytocin to achieve induction. Later studies

used combinations of cervical ripening with prostaglandins

or mechanical means, and subsequent oxytocin. Two stud-

ies used only prostaglandins for induction. In six trials,

women were only included if they had an unfavourable

cervix, and in five trials only women with a favourable cer-

vix were enrolled. The remaining trials did not use cervical

status as an inclusion criterion. The reported overall caesar-

ean section rates varied between studies, with a range of 1–47%. Compliance with treatment in the induction groups

was not uniformly high, with reported rates of <70% in six

of the trials. In almost all of the studies induction of labour

became necessary in many of the expectantly managed

patients. The reported rates varied from 4 to a high of

50%. Most trials reported that the time to delivery

increased in the expectantly managed versus the induced

groups, but this was not reported in a sufficiently uniform

manner to allow a quantitative summary. Typically, trials

reported latency to delivery of about 1 week in the expec-

tant management group. One trial reported no difference

in average gestational age at delivery between those induced

and those managed expectantly.30

A review of trial quality rated 19 trials as high quality

and 17 trials as low quality (Tables 1 and S2). One trial

could not be graded as sufficient information was not

available from the abstract, and the authors did not

respond to requests for additional information.24 The most

common reason for a low-quality score was unclear or

inadequate randomisation and allocation concealment. Of

the low-quality studies, six could not be included in the

meta-analysis either because of large post-randomisation

exclusions (>20%) or because of insufficient data to per-

form an intention-to-treat analysis. Only three trials docu-

mented a statistically significant difference in caesarean

section rates between a policy of induction and expectant

management. Two of these trials reported a reduction in

Citation Search 4

Records identified throughdatabase searching

(n = 2794)

Additional records identifiedthrough other sources

(n = 0)

Records after duplicates removed(n = 1368)

Records screened(n = 1368)

Records excludednot RCT (n = 292)

cervical ripening RCT(n = 321)

Induction method RCT(n = 346)

Term PROM RCT n = (71)Active management of

labour RCT (n = 27)other RCT (n=259)

non human RCT (n = 10)Full-text articles assessed

for eligibility(n = 42)

Full-text articles excluded,post dates cervical

ripening trials(n = 5)

Duplicate publication(n = 1)

Studies selected forreview of trial quality

(n = 37)

Studies included inquantitative synthesis

(meta-analysis)(n = 31)

Citation Search n = 2Eligible for inclusion n = 1

Figure 1. Flow diagram of studies included in the meta-analysis.

676 ª 2013 RCOG

Wood et al.

Table

1.Studycharacteristicsofrandomised

controlledtrialsofinductionin

subjectswithintact

mem

branes

Study

nStudypopulation

Methodofinduction

Caesarean

sectionrate:

induction

group%

(n)

Caesarean

sectionrate:

expectantgroup

%(n)

Quality

Included

inmeta-

analysis

Hen

ry39

112

Preg

nan

cy>40weeks

ofgestation

ARM/oxytocin

0(0)

1.8

(1)

Low

Yes

Cole

andcolleag

ues

33

237

Uncomplicated

pregnan

cy:39–4

0weeks

of

gestation

ARM/oxytocin

4.5

(5)

7.7

(9)

Low

Yes

Martinan

dcolleag

ues

43

230

Uncomplicated

pregnan

cy:39weeks

ofgestation

ARM/oxytocin

4.3

(4)

1.1

(1)

Low

No

Tylleskar

andcolleag

ues

50

84

Uncomplicated

pregnan

cy:40weeks

ofgestation

andfavourable

cervix

ARM/oxytocin

2.3

(1)

2.4

(1)

Low

No

Breartan

dcolleag

ues

21

716

Uncomplicated

pregnan

cy:37–3

9weeks

of

gestation

ARM/oxytocin

4.0

(19)

6.8

(16)

High

Yes

Katzan

dcolleag

ues

42

156

Uncomplicated

pregnan

cy:≥4

2weeks

ofgestation

andunfavourable

cervix

ARM/oxytocin

20.5

(16)

9(7)

Low

Yes

Sandean

dcolleag

ues

49

166

Uncomplicated

pregnan

cy:40–4

1weeks

of

gestationan

dfavourable

cervix

ARM/oxytocin

Unab

leto

calculate

Unab

leto

calculate

Low

No

Cardozo

andcolleag

ues

31

402

Uncomplicated

pregnan

cy:413/7

weeks

of

gestation

PGE3mgvaginally

�ARM/oxytocin

14.3

(28)

11.6

(24)

Low

No

Augen

senan

dcolleag

ues

29

Uncomplicated

pregnan

cy:42weeks

ofgestation

Oxytocin

6.5

(14)

10.3

(20)

High

Yes

Dysonan

dcolleag

ues

34

302

Uncomplicated

pregnan

cy:≥4

1weeks

ofgestation

andunfavourable

cervix

PGE3mgvaginally

or

0.5

mgintracervically/

oxytocin

14.5

(22)

27.3

(41)

High

Yes

Witteran

dWeitz

51

200

Uncomplicated

pregnan

cy:42weeks

ofgestation

Oxytocin

29.2

(30)

27.8

(27)

High

Yes

Bergsjoan

dcolleag

ues

30

188

Uncomplicated

pregnan

cy:≥4

2weeks

ofgestation

Oxytocin

28.7

(27)

41.4

(39)

Low

Yes

Egarteran

dcolleag

ues

27

345

Uncomplicated

pregnan

cy:42weeks

ofgestation

andfavourable

cervix

PGE3mgvaginally

1.1

(2)

1.8

(3)

Low

Yes

Martinan

dcolleag

ues

44

22

Uncomplicated

pregnan

cy:≥4

1weeks

ofgestation

andunfavourable

cervix

Laminaria/ARM/

oxytocin

16.7

(2)

10(1)

High

Yes

Hed

enan

dcolleag

ues

37

238

Uncomplicated

pregnan

cy:42weeks

ofgestation

andcervical

dilatation<4cm

ARM/oxytocin

9.2

(10)

7.0

(9)

Low

Yes

Han

nah

andcolleag

ues

36

3407

Uncomplicated

pregnan

cy:41–4

4weeks

of

gestationan

dcervix

<3cm

dilated

ARM/oxytocin

PGE2

0.5

mg

intracervically

21.1%

(360)

24.5%

(418)

High

yes

Herab

utyaan

d

colleag

ues

40

108

Uncomplicated

pregnan

cy:42weeks

ofgestation

andunfavourable

cervix

PGE2

0.5

mgintracervically/

oxytocin

47.4

(27)

47.1

(24)

Low

Yes

Kjosan

dcolleag

ues

53

200

Insulin-req

uiringdiabetes,includingGDM,

38weeks

ofgestation

PGE3mg/oxytocin

25(25)

31(31)

Low

Yes

McN

ellis

andcolleag

ues

45

440

Uncomplicated

pregnan

cy:41–4

3weeks

of

gestationan

dunfavourable

cervix

PGE0.5

mgintracervically/

oxytocin

20.8

(55)

18.3

(32)

High

Yes

Ohel

andcolleag

ues

47

200

Uncomplicated

pregnan

cy:40weeks

of

gestation�

4days

PGE3mgintravag

inally

Unab

leto

calculate

5.8

(6)

Low

No

ª 2013 RCOG 677

Induction of labour and caesarean section

Table

1.(Continued

)

Study

nStudypopulation

Methodofinduction

Caesarean

sectionrate:

induction

group%

(n)

Caesarean

sectionrate:

expectantgroup

%(n)

Quality

Included

inmeta-

analysis

Gonen

andcolleag

ues

52

284

Uncomplicated

pregnan

cy:38weeks

ofgestation

andEFW

4000–4

500g

PGE/oxytocin

19.4

(26)

21.6

(30)

Low

Yes

Roachan

dRogers4

8201

Uncomplicated

pregnan

cy:42weeks

ofgestation

PGE3mgintravag

inally

16.7

(16)

17.1

(18)

High

Yes

Aman

oan

dcolleag

ues

28

194

Uncomplicated

nullipara:

39weeks

ofgestation

Laminaria/oralPG

E/

IVPG

F2a/oxytocin

6.3

(4)

5.6

(4)

Low

No

Suzuki

andcolleag

ues

55

36

Twin

pregnan

cy:37weeks

ofgestation,with

cephalic-firsttw

in

PGE0.5

mgorally/

oxytocin

17.6

(3)

31.6

(6)

Low

Yes

James

andcolleag

ues

41

74

Uncomplicated

pregnan

cy:41weeks

ofgestation

IntracervicalFoley

catheter/oxytocin

5.4

(2)

10.8

(4)

High

Yes

Chan

rachakulan

d

Herab

utya32

250

Uncomplicated

pregnan

cy:413/7

weeks

of

gestation,withfavourable

cervix

ARM/oxytocin

26.6

(33)

21.6

(27)

Low

Yes

Ekan

dcolleag

ues

54

54

Oligohydramnios(AFI

<5cm

)at

41weeks

of

gestation

IntracervicalFoley

catheter/oxytocin

3.5

(1)

15.4

(4)

High

Yes

Gelisen

andcolleag

ues

35

600

Uncomplicated

pregnan

cy:41weeks

ofgestation,

withunfavourable

cervix

IntracervicalFoley

catheter/m

isoprostol

50lgvaginally/oxytocin

19.3

(58)

22(66)

High

Yes

Nielsen

andcolleag

ues

46

216

Uncomplicated

pregnan

cy:≥3

9weeks

ofgestation,

withfavourable

cervix

ARM/oxytocin

6.9

(8)

7.2

(8)

High

Yes

Van

den

Hove

and

colleag

ues

57

33

SuspectedIUGR≥3

7weeks

ofgestation

PGE/ARM/oxytocin

18.8

(3)

23.5

(4)

High

Yes

Heimstad

and

colleag

ues

38

508

Uncomplicated

pregnan

cy:412/7

weeks

of

gestation

PGE0.5

mgor

misoprostol50lg/ARM/

oxytocin

11.0

(28)

13.0

(33)

High

Yes

Nicholsonan

d

colleag

ues

59

270

374/7

weeks

ofgestationan

dhighrisk

for

caesareansection

PGE(dinoprostoneor

misoprostol/A

RM/oxytocin)

10.3

(14)

14.9

(20)

High

Yes

Koopman

san

d

colleag

ues

58

756

Mild

PIH

at36–4

1weeks

ofgestation

Intracervicalorintravag

inal

PGE/intracervicalFoley

catheter/oxytocin

14.3

(54)

19.0

(72)

High

Yes

Boersan

dcolleag

ues

56

650

SuspectedIUGRat

36–4

1weeks

ofgestation

Intravag

inal

orintracervical

PGE/intracervicalFoley

catheter/oxytocin

14.0

(45)

13.7

(45)

High

Yes

Ben

ito-Reyes

and

colleag

ues

22

200

Uncomplicated

pregnan

cy:>42weeks

ofgestation,

withunfavourable

cervix

PGE2

/ARM/oxytocin

12.7

(13)

18.4

(18)

High

Yes

Boulvainan

dcolleag

ues

24

817

Uncomplicated

pregnan

cy:37–3

8weeks

of

gestation,EFW

>95%.

Datanotavailable

28.0

(114)

31.7

(130)

Yes

Doddan

dcolleag

ues

26

149

Twin

pregnan

cy:≥3

7weeks

ofgestation

Nodetailsprovided

31(22)

26.9

(21)

High

Yes

678 ª 2013 RCOG

Wood et al.

the rate of caesarean section with induction,34,36 and one

reported an increase in risk.42 The remaining trials reported

non-significant differences in the rate of caesarean section,

with most point estimates favouring a reduction in risk

with induction. A quantitative summary analysis combined

the results of 31 trials, with 6248 women randomised to

induction and 5918 women randomised to expectant man-

agement (Figure 2). The trials were ordered by year in

order to display any potential chronological effect, and

were subdivided by post-dates trials (≥41 weeks of gesta-

tion) and induction for other indications. In this analysis, a

policy of induction was associated with a reduction in the

risk of caesarean section compared with expectant manage-

ment (fixed-effects model, OR 0.83, 95% CI 0.76–0.92,P = 0.0002). There was no significant statistical heterogene-

ity: v² = 27.11, df = 30, P = 0.62, and I2 = 0%. The same

results were obtained with a random-effects model

(OR 0.83, 95% CI 0.76–0.92). Visual inspection of the fun-

nel plot did not suggest any significant publication bias.

The reduced risk of caesarean section was seen in both the

subgroups of the post-dates trials (OR 0.85, 95% CI 0.76–0.95) and in the trials of induction for other indications

(OR 0.81, 95% CI 0.69–0.95). Subgroup analysis of only

the 19 high-quality trials revealed a similar result (fixed-ef-

fects model, OR 0.82 95% CI 0.73–0.91; random-effects

model, OR 0.82, 95% CI 0.73–0.91; Figure 3).

Details on the indication for caesarean section were

reported in 16 of the trials; however, in the majority the

number of outcomes was too few for any meaningful com-

parisons. Of the seven trials with sufficient numbers, three

reported an increase in the number of caesarean sections for

fetal distress in the expectant group, but this difference was

statistically significant in only one study.36,40,56 One trial

reported a non-significant increase in the risk of abdominal

delivery for dystocia with expectant management.59 The

remaining trials did not report any differences in indica-

tions for caesarean section between those randomised to

induction or those randomised to expectant management.

Meta-analysis of the risk of caesarean section for fetal

distress with induction versus expectant management did

not document a statistically significant difference (Fig-

ure 4). A meta-analysis was also performed for the out-

comes of postpartum haemorrhage and operative vaginal

delivery (Figure 4): neither was increased with induction of

labour. Neonatal outcomes were also examined. A compos-

ite neonatal morbidity score was described in seven trials,

but only one reported a statistically significant difference

between the study groups,24 which, in that study, favoured

the induction arm. Unfortunately, the morbidity scores

were not sufficiently similar to allow for a pooled analysis.

Some assessment of cord pH was reported in 13 trials. One

trial reported an increase in the rate of cord pH < 7.05

with expectant management 6% (19) versus 3% (9),

P = 0.043.58 The other trials reported non-significant dif-

ferences in mean pH or in the rate of low cord pH. As a

result of variable reporting between the trials, meta-analysis

was not feasible. Meta-analysis was performed for the fol-

lowing neonatal outcomes: an Apgar score at 5 min-

utes < 7; admission to the neonatal intensive care unit

(NICU); and perinatal death, excluding anomaly (Fig-

ure 4). No statistically significant differences between

induction and expectant management were observed. Peri-

natal death was reduced with induction of labour, but the

result was not statistically significant P = 0.05.

Discussion

Main findingsOur meta-analysis of clinical trials of induction versus

expectant management in women with intact membranes

found that the induction of labour is associated with a

moderate but statistically significant reduction in the risk

of caesarean section. This effect was evident in the sub-

groups of post-date trials, trials of induction for other indi-

cations, and in the analysis restricted to high-quality

studies. Differences in other maternal and neonatal out-

comes were not evident, but a non-statistically significant

reduction in perinatal death was observed in the induction

group.

Strengths and limitationsOur review’s main strength is that it included all relevant

randomised clinical trials that we identified, and so added

to previous reviews by including reports in all languages as

well as those published since 2007. As our results are based

solely on randomised clinical trials, selection bias and con-

founding should be limited. This is in contrast to observa-

tional studies where selection bias and confounding can be

problematic. Admittedly, recent well-designed retrospective

studies in electively induced women, have also demon-

strated a reduction in caesarean section with induction,

compared with expectant management.60,61

Our results were based on an intention-to-treat analysis.

Although this is a valid standard, it could also have affected

our findings. In most of the trials there was less than per-

fect compliance with induction in the treatment groups,

and there were high rates of induction in the expectant

groups. These factors would tend to bias the results

towards the null, and therefore could have obscured a true

difference in the risk of caesarean section with induction.

A limitation of our review is that we did not include a

formal systematic review of cost effectiveness. Two of the

trials we reviewed, the Canadian Post Term Pregnancy

Trial and Hypertension and Pre-eclampsia Intervention

Trial at Term (HYPITAT), have published secondary eco-

nomic analyses.62,63 Both of these analyses found that the

ª 2013 RCOG 679

Induction of labour and caesarean section

increase in costs associated with induction of labour were

more than offset by a reduction in the frequency of fetal

testing. These results may not apply to term elective induc-

tions, but may be similar for induction for indications such

as small for gestational age (SGA), multiple pregnancy, and

maternal diabetes.

InterpretationSome caution should be sounded before unreservedly

accepting the conclusion that induction of labour reduces

the risk of caesarean section. In our meta-analysis, this

result, especially in the post-date trials, is heavily influenced

by the largest study in our review, the Canadian Post Dates

Figure 2. Forest plot for the outcome ‘caesarean section’ in the selected trials, comparing a policy of induction of labour with that of expectant

management.

680 ª 2013 RCOG

Wood et al.

Figure 3. Forest plot for the outcome ‘caesarean section’ in high-quality trials only, comparing a policy of induction of labour with expectant

management.

No. of SummaryStudies Events Total Events Total Odds Ratio (95% CI)

Maternal outcomes

Post partum hemmorhage 5 87 1569 107 1331 0.78 [0.58, 1.05]

Operative vaginal delivery 20 871 4535 761 4281 1.09 [0.98, 1.22]

Cesarean section for fetal distress 16 236 3765 293 3744 0.87 [0.62, 1.23]

Neonatal outcomes

0.93 [0.63, 1.37]41375241134818APGAR <7 (5 min)

0.88 [0.75, 1.03]3958379404133715NICU admission

0.37 [0.14, 1.00]5860106194130Perinatal death*

*excluding anomaly

Induction Expectant managementOdds ratio (95% CI)

Figure 4. Summary odds ratios and 95% confidence intervals for selected secondary maternal and neonatal outcomes.

ª 2013 RCOG 681

Induction of labour and caesarean section

Trial,36 where cervical ripening with intracervical prosta-

glandin E was only planned for women in the immediate

induction group. Similar treatment was discouraged for

inductions in women who were expectantly managed. Even-

tually 32% of the expectant group were induced, but only

9% received prostaglandins for ripening, compared with

51% of the immediate induction group. In a recent Cochra-

ne review, cervical ripening with intracervical prostaglandins

was reported to reduce the risk of caesarean section com-

pared with oxytocin alone.64 Therefore, this co-intervention

in the induction group may have biased their results. Addi-

tionally, a disproportionate number of women in the expec-

tant group had induction for suspected fetal compromise.65

A similar trend was noted in our meta-analysis. Although

many of these were likely to be false-positive results, the

higher gestational ages in women who were expectantly

managed may have increased the anxiety of doctors, and led

to a greater number of caesarean sections. Similar labelling

has been documented as a factor in increasing the rate of

caesarean sections in women with gestational diabetes and

suspected macrosomia.66,67 Such concern about poor out-

comes may affect delivery decisions for expectantly managed

women with PIH, SGA, oligohydramnios, and multiple

pregnancy. It may be that the results of our review reflect

doctors’ discomfort with delayed delivery in high-risk

women that, once they are in labour, manifests as more fre-

quent caesarean sections: an example of research confirming

the biases of the health care community.68

It is difficult to reconcile the results of this meta-analysis

with the consistent finding that lack of cervical maturation

prior to induction is strongly associated with subsequent cae-

sarean section.69,70 Clinicians have generally pursued a policy

of expectant management, not only to allow spontaneous

labour, but also to provide time for cervical ripening should

induction become necessary later. Therefore, a policy of

delay would be expected to produce an improvement in cer-

vical state and related reduction in the risk of caesarean sec-

tion. A few possible explanations can be postulated to resolve

this paradox. First, although ripening would have eventually

occurred in many of expectantly managed women, the actual

delay to delivery was too short: most of the included trials

documented only modest differences between treatment

groups in gestational age at delivery. A second explanation is

that cervical state is a characteristic of the patient that is not

modifiable by expectant management. Support for this sup-

position comes from Smith and colleagues’s.71 fascinating

cohort study, which found that greater cervical length at

mid-gestation in primiparous women was associated with an

increased risk of caesarean section at term, and that this was

largely because of poor progress in labour. Ultimately, either

one of these possibilities could explain both why the trials

that included only women with unripe cervixes had similar

findings as those restricted to women with mature cervixes,

and the result of a subgroup analysis of Koopman and col-

leagues’s.58 trial, which found no differences in the risk of

caesarean section stratified by Bishop score.

Conclusion

Some readers may feel that the results of the trials and this

meta-analysis are sufficient to justify a policy of elective

induction. Before concluding this, it should also be care-

fully considered that only one of the trials was designed to

evaluate the impact of induction on the risk of caesarean

section.59 Ideally, we feel that a trial primarily evaluating

the risk of caesarean section would have a number of fea-

tures that were not prominent in the trials where it was a

secondary outcome. First, cervical state should not be

known by the recruiting clinicians, or even by the women

themselves. This would reduce the significant risk of

pre-randomisation exclusions of women with the most

adverse cervical findings. Secondly, the latency to delivery

in the expectant group should be sufficient both for a

meaningful improvement in cervical state and for a signifi-

cant number of women to go into labour spontaneously.

This can only be achieved if the treatment group is induced

when fetal maturation is assured (at 38 weeks of gestation?)

and the women are of sufficiently low risk to anticipate a

delay in induction until at least 41 weeks of gestation. Fur-

thermore, there needs to be a strong commitment at study

sites to perform what might be perceived as ‘elective’

inductions in a timely fashion to reduce crossover. Finally,

an economic evaluation conducted alongside the trial will

be important. Until such rigorous trials are performed we

think it is premature to conclude that induction does not

affect the risk of caesarean section.

Ultimately, induction of labour is one of the common

treatments available to clinicians. It could also be argued

that, based on our results, it is one of the only interven-

tions that has been shown in a clinical trial to reduce the

risk of caesarean section.72 Therefore, it may be that some

women at high risk of caesarean section, such as women of

late maternal age or women who are obese, could benefit

from an elective induction. Ideally, this will be the subject

of further clinical trials.

Disclosure of interestsThe authors have no interests to disclose.

Contribution to authorshipAll authors contributed to the design of the study. SW and

SC reviewed all of the abstracts. All of the authors critically

appraised the selected articles. SW performed the statistical

analysis, and all the authors contributed to the interpreta-

tion of the results. SW drafted the article, which was

reviewed by SC and RS.

682 ª 2013 RCOG

Wood et al.

Details of ethics approvalThe study was approved by the local ethics review board

(ref. no. E–23622).

FundingThe authors are members of the Partnership for Research

and Education in Mothers and Infants, which has been

funded by Ross Products, a division of Abbott.

AcknowledgementsThe authors wish to acknowledge the financial support of

their research group by Ross Products, a division of Ab-

bott. The authors also wish to thank Dr Magali Robert, Dr

Vreni Kuret, and Dr Eliana Castillo for their assistance with

reviewing the French, German, and Spanish articles. The

authors would also like to thank Ms Selphee Tang for assis-

tance with the figures.

Supporting Information

Additional Supporting Information may be found in the

online version of this article:

Table S1. Study characteristics of randomised controlled

trials of induction in subjects with intact membranes.

Table S2. Quality assessment of randomised controlled

trials of induction in subjects with intact membranes. &

References

1 Guihard P, Blondel B. Trends in risk factors for caesarean sections in

France between 1981 and 1995: lessons for reducing the rates in

the future. BJOG 2001;108:48–55.

2 Queenan JT. How to stop the relentless rise in cesarean deliveries.

Obstet Gynecol 2011;118:199–200.

3 Rayburn WF, Zhang J. Rising rates of labor induction: present

concerns and future strategies. Obstet Gynecol 2002;100:164–7.

4 Zhang J, Troendle J, Reddy UM, Laughon SK, Branch DW, Burkman

R, et al. Contemporary cesarean delivery practice in the United

States. Am J Obstet Gynecol 2010;203:326.

5 Singh R, Nath TA. Is the caesarean section rate a performance

indicator of an obstetric unit? J Matern Fetal Neonatal Med

2011;24:204–7.

6 Boulvain M, Marcoux S, Bureau M, Fortier M, Fraser W. Risks of

induction of labour in uncomplicated term pregnancies. Paediatr

Perinat Epidemiol 2001;15:131–8.

7 Dublin S, Lydon-Rochelle M, Kaplan RC, Watts DH, Critchlow CW.

Maternal and neonatal outcomes after induction of labor without

an identified indication. Am J Obstet Gynecol 2000;183:986–94.

8 Heffner LJ, Elkin E, Fretts RC. Impact of labor induction, gestational

age, and maternal age on cesarean delivery rates. Obstet Gynecol

2003;102:287–93.

9 Maslow AS, Sweeny AL. Elective induction of labor as a risk factor

for cesarean delivery among low-risk women at term. Obstet

Gynecol 2000;1:917–22.

10 Vahratian A, Zhang J, Troendle JF, Sciscione AC, Hoffman MK.

Labor progression and risk of cesarean delivery in electively induced

nulliparas. Obstet Gynecol 2005;105:698–704.

11 Yeast JD, Jones A, Poskin M. Induction of labor and the relationship

to cesarean delivery: A review of 7001 consecutive inductions. Am J

Obstet Gynecol 1999;1:628–33.

12 Caughey AB, Nicholson JM, Cheng YW, Lyell DJ, Washington AE,

Caughey AB, et al. Induction of labor and cesarean delivery by

gestational age. Am J Obstet Gynecol 2006;195:700–5.

13 Glantz JC, Glantz JC. Term labor induction compared with

expectant management. Obstet Gynecol 2010;115:70–6.

14 Dare MR, Middleton P, Crowther CA, Flenady VJ, Varatharaju B.

Planned early birth versus expectant management (waiting) for

prelabour rupture of membranes at term (37 weeks or more).

Cochrane Database of Syst Rev 2006;(1):CD005302.

15 Hannah ME, Ohlsson A, Farine D, Hewson SA, Hodnett ED, Myhr

TL, et al. Induction of labor compared with expectant management

for prelabor rupture of the membranes at term. TERMPROM study

group. N Engl J Med 1996;334:1005–10.

16 Challis JRG, Sloboda DM, Alfaidy N, Lye SJ, Gibb W, Patel FA, et al.

Prostaglandins and mechanisms of preterm birth. Reproduction

2002;124:1–17.

17 Gulmezoglu AM, Crowther CA, Middleton P. Induction of labour for

improving birth outcomes for women at or beyond term. Cochrane

Database of Syst Rev 2006;(4):CD004945.

18 Caughey AB, Sundaram V, Kaimal AJ, Gienger A, Cheng YW,

McDonald KM, et al. Systematic review: elective induction of labor

versus expectant management of pregnancy. Ann Intern Med

2009;151:252–63.

19 Juni P, Altman DG, Egger M. Systematic reviews in health care:

assessing the quality of controlled clinical trials. BMJ 2001;323:42–6.

20 Husslein P, Egarter C, Sevelda P. Induction of labour with

prostaglandin E2 vvaginal tablets - A revival of elective induction?

Results of prospective randomised trial Geburtshilfe Frauenheilkd

1986;46:83–7.

21 Breart G, Goujard J, Maillard F, Chavigny C, Rumeau-Rouquette C,

Sureau C. Comparison of 2 obstetrical attitudes vis-a-vis inducing

labor at term. Randomized study. J Gynecol Obstet Biol Reprod

1982;11:107–12.

22 Benito R V, Hurtado MR, Rodriguez RF, Reyes SD, Alvarez Leon EE,

Garcia Hernandez JA. Elective termination versus expectant

management in prolonged pregnancy: a prospective study of 200

pregnant women. Progresos de Obstetricia Y Ginecologia

2010;53:446–53.

23 Suikkari AM, Jalkanen M, Heiskala H, Koskela O. Prolonged

pregnancy: induction or observation. Acta Obstet Gynecol Scand

Suppl 1983;116:58.

24 Boulvain M, Senat M-V, Rozenberg P, Irion O. Induction of labor or

expectant management for large-for-dates fetuses: a randomized

controlled trial. Am J Obstet Gynecol 2012;206(S1):2.

25 Dodd JM, Crowther CA, Haslam RR, Robinson JS. Timing of birth for

women with a twin pregnancy at term: a randomised controlled

trial. BMC pregnancy childbirth 2010;10:68.

26 Dodd JM, Crowther CA, Haslam RR, Robinson JS. Elective birth at

37 weeks of gestation versus standard care for women with an

uncomplicated twin pregnancy at term: the twins timing of birth

randomised trial. BJOG 2012;119:964–73.

27 Egarter C, Kofler E, Fitz R, Husslein P. Is induction of labor indicated

in prolonged pregnancy? Results of a prospective randomised trial

Gynecol Obstet Invest 1989;27:6–9.

28 Amano K, Saito K, Shoda T, Tani A, Yoshihara H, Nishijima M.

Elective induction of labor at 39 weeks of gestation: a prospective

randomized trial. J Obstet Gynaecol Res 1999;25:33–7.

29 Augensen K, Bergsjo P, Eikeland T, Askvik K, Carlsen J. Randomised

comparison of early versus late induction of labour in post-term

pregnancy. Br Med (Clin Res Ed) 1987;294:1192–5.

ª 2013 RCOG 683

Induction of labour and caesarean section

30 Bergsjo P, Gui-dan H, Su-qin Y, Zhi-zeng G, Bakketeig LS.

Comparison of induced versus non-induced labor in post-term

pregnancy. A randomized prospective study. Acta Obstet Gynecol

Scand 1989;68:683–7.

31 Cardozo L, Fysh J, Pearce JM. Prolonged pregnancy: the

management debate. BMJ 1986;293:1059–63.

32 Chanrachakul B, Herabutya Y. Postterm with favorable cervix: is

induction necessary? Eur J Obstet Gynecol Reprod Biol

2003;106:154–7.

33 Cole RA, Howie PW, Macnaughton MC. Elective induction of

labour. A randomised prospective trial. Lancet 1975;1:767–70.

34 Dyson DC, Miller PD, Armstrong MA. Management of prolonged

pregnancy: induction of labor versus antepartum fetal testing. Am J

Obstet Gynecol 1987;156:928–34.

35 Gelisen O, Caliskan E, Dilbaz S, Ozdas E, Dilbaz B, Ozdas E, et al.

Induction of labor with three different techniques at 41 weeks of

gestation or spontaneous follow-up until 42 weeks in women with

definitely unfavorable cervical scores. Eur J Obstet Gynecol Reprod

Biol 2005;120:164–9.

36 Hannah ME, Hannah WJ, Hellmann J, Hewson S, Milner R, Willan A.

Induction of labor as compared with serial antenatal monitoring in

post-term pregnancy. A randomized controlled trial. The Canadian

multicenter post-term pregnancy trial group. N Engl J Med

1992;326:1587–92.

37 Heden L, Ingemarsson I, Ahlstrom H, Solum T. Induction of labor

versus conservative management in prolonged pregnancy: controlled

study. International Journal of Feto-Maternal Medicine 1991;4:231–6.

38 Heimstad R, Skogvoll E, Mattsson L-A, Johansen OJ, Eik-Nes SH,

Salvesen KA. Induction of labor or serial antenatal fetal monitoring

in postterm pregnancy: a randomized controlled trial. Obstet

Gynecol 2007;109:609–17.

39 Henry GR. A controlled trial of surgical induction of labour and

amnioscopy in the management of prolonged pregnancy. J Obstet

Gynaecol Br Commonw 1969;76:795–8.

40 Herabutya Y, Prasertsawat PO, Tongyai T, Isarangura Na Ayudthya

N. Prolonged pregnancy: the management dilemma. Int J Gynaecol

Obstet 1992;37:253–8.

41 James C, George SS, Gaunekar N, Seshadri L. Management of

prolonged pregnancy: a randomized trial of induction of labour and

antepartum foetal monitoring. Natl Med J India 2001;14:270–3.

42 Katz Z, Yemini M, Lancet M, Mogilner BM, Ben-Hur H, Caspi B.

Non-aggressive management of post-date pregnancies. Eur J Obstet

Gynecol Reprod Biol 1983;15:71–9.

43 Martin DH, Thompson W, Pinkerton JH, Watson JD. A randomized

controlled trial of selective planned delivery. Br J Obstet Gynaecol

1978;85:109–13.

44 Martin JNJr, Sessums JK, Howard P, Martin RW, Morrison JC.

Alternative approaches to the management of gravidas with

prolonged-postterm-postdate pregnancies. J Miss State Med Assoc

1989;30:105–11.

45 McNellis D, Medearis AL, Fowler S, Romero R, Sibai BM, Caritis SN,

et al. A clinical trial of induction of labor versus expectant

management in postterm pregnancy: the national institute of child

health and human development network of maternal-fetal medicine

units. Am J Obstet Gynecol 1994;170:716–23.

46 Nielsen PE, Howard BC, Hill CC, Larson PL, Holland RH, Smith PN.

Comparison of elective induction of labor with favorable Bishop

scores versus expectant management: a randomized clinical trial. J

Matern Fetal Neonatal Med 2005;18:59–64.

47 Ohel G, Rahav D, Rothbart H, Ruach M. Randomised trial of

outpatient induction of labor with vaginal PGE2 at 40-41 weeks of

gestation versus expectant management. Arch Gynecol Obstet

1996;258:109–12.

48 Roach VJ, Rogers MS. Pregnancy outcome beyond 41 weeks

gestation. Int J Gynaecol Obstet 1997;59:19–24.

49 Sande HA, Tuveng J, Fonstelien T. A prospective randomized study

of induction of labor. Int J Gynecol Obstet 1983;21:333–6.

50 Tylleskar J, Finnstrom O, Leijon I. Spontaneous labor and elective

induction - a prospective randomized study. I. Effects on mother

and fetus. Acta Obstet Gynecol Scand 1979;58:513–8.

51 Witter FR, Weitz CM. A randomized trial of induction at 42 weeks

gestation versus expectant management for postdates pregnancies.

Am J Perinatol 1987;4:206–11.

52 Gonen O, Rosen DJD, Dolfin Z, Tepper R, Markov S, Fejgin MD.

Induction of labor versus expectant management in macrosomia: a

randomized study. Obstet Gynecol 1997;89:913–7.

53 Kjos SL, Henry OA, Montoro M, Buchanan TA, Mestman JH.

Insulin-requiring diabetes in pregnancy: a randomized trial of active

induction of labor and expectant management. Am J Obstet

Gynecol 1993;169:611–5.

54 Ek S, Andersson A, Johansson A, Kublicas M. Oligohydramnios in

uncomplicated pregnancies beyond 40 completed weeks. A

prospective, randomised, pilot study on maternal and neonatal

outcomes. Fetal Diagn Ther 2005;20:182–5.

55 Suzuki S, Otsubo Y, Sawa R, Yoneyama Y, Araki T. Clinical trial of

induction of labor versus expectant management in twin pregnancy.

Gynecol Obstet Invest 2000;49:24–7.

56 Boers KE, Vijgen SM, Bijlenga D, van der Post JA, Bekedam DJ,

Kwee A, et al. Induction versus expectant monitoring for

intrauterine growth restriction at term: randomised equivalence trial

(DIGITAT). BMJ 2010;341:c7087.

57 van den Hove MM, Willekes C, Roumen FJ, Scherjon SA. Intrauterine

growth restriction at term: induction or spontaneous labour? Dis-

proportionate intrauterine growth intervention trial at term (DIGITAT): a

pilot study Eur J Obstet Gynecol Reprod Biol 2006;125:54–8.

58 Koopmans CM, Bijlenga D, Groen H, Vijgen SM, Aarnoudse JG,

Bekedam DJ, et al. Induction of labour versus expectant monitoring

for gestational hypertension or mild pre-eclampsia after 36 weeks’

gestation (HYPITAT): a multicentre, open-label randomised

controlled trial. Lancet 2009;374:979–88.

59 Nicholson JM, Parry S, Caughey AB, Rosen S, Keen A, Macones GA.

The impact of the active management of risk in pregnancy at term

on birth outcomes: a randomized clinical trial. Am J Obstet Gynecol

2008;198:511–5.

60 Cheng YW, Kaimal AJ, Snowden JM, Nicholson JM, Caughey AB.

Induction of labor compared to expectant management in low-risk

women and associated perinatal outcomes. Am J Obstet Gynecol

2012;207:502–8.

61 Stock SJ, Ferguson E, Duffy A, Ford I, Chalmers J, Norman JE.

Outcomes of elective induction of labour compared with expectant

management: population based study. BMJ 2012;344:e2838.

62 Goeree R, Hannah M, Hewson S. Cost-effectiveness of induction of

labour versus serial antenatal monitoring in the Canadian

multicentre postterm pregnancy trial. CMAJ 1995;152:1445–50.

63 Vijgen SM, Koopmans CM, Opmeer BC, Groen H, Bijlenga D,

Aarnoudse JG, et al. An economic analysis of induction of labour

and expectant monitoring in women with gestational hypertension

or pre-eclampsia at term (HYPITAT trial). BJOG 2010;117:1577–85.

64 Alfirevic Z, Kelly AJ, Dowswell T. Intravenous oxytocin alone for

cervical ripening and induction of labour. Cochrane Database of Syst

Rev 2009;(4):CD003246.

65 Menticoglou SM, Hall PF. Routine induction of labour at 41 weeks

gestation: nonsensus consensus. BJOG 2002;109:485–91.

66 Melamed N, Yogev Y, Meizner I, Mashiach R, Ben-Haroush A.

Sonographic prediction of fetal macrosomia: the consequences of

false diagnosis. J Ultrasound Med 2010;29:225–30.

684 ª 2013 RCOG

Wood et al.

67 Naylor CD, Sermer M, Chen E, Sykora K. Cesarean delivery in

relation to birth weight and gestational glucose tolerance:

pathophysiology or practice style? Toronto trihospital gestational

diabetes investigators JAMA 1996;275:1165–70.

68 Ioannidis JPA. Why most published research findings are false. PLOS

Med 2005;2:0696–701.

69 Bishop EH. Pelvic scoring for elective induction. Obstet Gynecol

1964;24:266–8.

70 Laughon SK, Zhang J, Troendle J, Sun L, Reddy UM. Using a simplified

Bishop score to predict vaginal delivery. Obstet Gynecol 2011;117:805–11.

71 Smith GC, Celik E, To M, Khouri O, Nicolaides KH, Fetal Medicine

Foundation Second Trimester Screening Group. Cervical length at

mid-pregnancy and the risk of primary cesarean delivery. N Engl J

Med 2008;358:1346–53.

72 Chaillet N, Dumont A. Evidence-based strategies for reducing

cesarean section rates: a meta-analysis. Birth 2007;34:53–64.

Mini commentary on ‘Does induction of labour increase the risk ofcaesarean section? A systematic review and meta-analysis of trialsin women with intact membranes’

S DowneResearch in Childbirth and Health Group, University of Central Lancashire, Preston, UK

There is global interest in reducing cae-

sarean section rates. As Wood and col-

leagues note, studies of induction of

labour have variously reported both

increased and decreased caesarean rates.

The authors have undertaken a careful

and thorough meta-analysis, and have

shown consistent results in favour of

labour induction; however, they are jus-

tifiably cautious about the policy impli-

cations of their findings, on the basis

that the results may arise from

non-treatment effects. They propose

more better-designed studies. Very

importantly, they note the need for

future research to include cost-effective-

ness analyses, and an assessment of

women’s views and experiences.

Apart from these factors, future stud-

ies should also assess unanticipated

long-term outcomes for mother and

baby. For example, there is growing evi-

dence that so-called ‘late prematurity’

(37–38 weeks of gestation) may be

linked to a range of adverse outcomes for

infants in the longer term (Boyle et al.

BMJ 2012;344:e896). This is important,

given the known margin of error in dat-

ing of any particular pregnancy. Factors

that may independently affect labour

management decisions (and, conse-

quently, policy implementation deci-

sions) should also be taken into account.

For example, a study of associations

between induction of labour and rates of

caesarean section in the USA found that

the results varied with sociodemograph-

ics (parity, age, race, and education),

maternal behaviours (number of prena-

tal visits), and, intriguingly, service

design factors, such as hospital teaching

status and ownership (Wilson et al. J

Nurs Scholarship 2010;42:130–138).

Wood et al. comment that induction

of labour seems to be the only technique

that has successfully reduced caesarean

section in the context of a randomised

controlled trial (RCT). This is not, in

fact, the case. The current Cochrane

review of continuous labour support

(Hodnett et al. Cochrane Database Syst

Rev 2012: art. no.: CD000012. DOI 10.

1002/14651858.CD000012.pub4) shows a

reduction in caesarean section rate that

is very similar to that found by Wood

et al. (OR 0.78, 95% CI 0.67–0.91).RCTs of place of birth, and, particularly,

home birth, are notoriously hard to set

up. In the next-best approach, the popu-

lation-based birthplace study found very

significant reductions in caesarean sec-

tion for planned birth centres or home

births, when compared with hospital

births [ranging from an adjusted OR of

0.31 (95% CI 0.23–0.41) for a planned

homebirth to 0.39 (95% CI 0.29–0.53)for a planned birth in a birth centres],

with no increase in adverse outcomes,

except among neonates born at home to

primiparous women. These data suggest

that the mechanism that underlies high

and rising caesarean section rates is likely

to include local childbirth philosophies

and management approaches, as much

as maternal and fetal physiology.

In conclusion, in addition to the fac-

tors suggested by Wood et al., future

studies of the impact of induction of

labour on caesarean section rates should

take into account the contextual factors

and longer-term outcome measures

identified above. Indeed, it may be pre-

mature to undertake such studies at all,

until there is a more precise understand-

ing of the mechanisms that underpin

high and rising caesarean section rates,

and the consequent identification of fac-

tors that could plausibly be addressed by

additional interventions such as contin-

uous labour support, place of birth, and

labour induction.

Disclosure of interestsI am a co-author on the current Coch-

rane review of alternative versus con-

ventional institutional settings for

birth, and of a structured review of the

outcomes of free-standing, midwife-led

birth centres. I was the founding Chair

of the Royal College of Midwives Cam-

paign for Normal Birth. I have no

financial interests in any of the issues

discussed in the commentary above.&

ª 2013 RCOG 685

Induction of labour and caesarean section