Induction of labor versus expectant management for post-date …americas.evipnet.wikibvs.org/img_auth.php/d/db/6.pdf · 2013-03-07 · REVIEW ARTICLE Induction of labor versus expectant

REVIEW ARTICLE

Induction of labor versus expectant management for post-datepregnancy: Is there sufficient evidence for a change in clinical practice?

ULLA-BRITT WENNERHOLM1, HENRIK HAGBERG1, BENGT BRORSSON2 &

CHRISTINA BERGH1

1Department of Obstetrics and Gynecology, the Institute of Clinical Sciences, Sahlgrenska University Hospital, Goteborg,

Sweden, and 2Department of Public Health and Caring Sciences, Akademiska sjukhuset, Uppsala, Sweden

AbstractObjectives. To compare perinatal and maternal outcomes between elective induction of labor versus expectant managementof pregnancies at 41 weeks and beyond. Design. Systematic review and meta-analysis. Methods. We searched PubMed,CINAHL, Cochrane Database of Systematic Reviews (CDSR), Database of Abstracts of Reviews of Effectiveness (DARE)and PsycINFO (1980 to November, 2007). Inclusion criteria were systematic reviews and randomized controlled trialscomparing elective induction of labor versus expectant management of pregnancies at 41 weeks and beyond. Three or morereviewers independently read and evaluated all selected studies. Data were extracted and analyzed using Review ManagerSoftware. Main outcome measures. Perinatal mortality. Results. Thirteen trials fulfilled the inclusion criteria for the meta-analysis. Elective induction of labor was not associated with lower risk of perinatal mortality compared to expectantmanagement (relative risks (RR): 0.33; 95% confidence intervals (CI): 0.10�1.09). Elective induction was associated with asignificantly lower rate of meconium aspiration syndrome (RR: 0.43; 95% CI: 0.23�0.79). More women randomized toexpectant management were delivered by cesarean section (RR: 0.87; 95% CI: 0.80�0.96). Conclusions. The meta-analysisillustrated a problem with rare outcomes such as perinatal mortality. No individual study with adequate sample size has beenpublished, nor would a meta-analysis based on the current literature be sufficient. The optimal management of pregnanciesat 41 weeks and beyond is thus unknown.

Key words: Post-term pregnancy, full-term pregnancy, induced labor, expectant management, perinatal death, meta-analyses

Introduction

Term pregnancy is defined as a pregnancy lasting

between 37 completed weeks and 41 weeks �6 days.

Pregnancies that reach or continue beyond 294 days

(42 gestational weeks) are described as post-term.

Five to ten percent of all pregnancies have been

considered post-term depending on diagnostic cri-

teria, dating policy and population investigated, but

the occurrence is declining in North America,

Australia and Europe, with the lowest recently

reported rate in Austria (0.4%) and the highest in

Denmark (8.1%) (1�3). This huge variation in post-

term pregnancy rate is also dependent on different

intervention strategies.

Post-term pregnancy conveys an increased risk of

perinatal mortality that is small in absolute terms

(4), but quite substantial (3- to 4-fold) if expressed

in relative numbers per fetus exposed in ongoing

pregnancies, rather than per delivery at each gesta-

tional week (4,5). The risk is particularly enhanced

for primiparas and in pregnancies complicated by

intrauterine growth restriction (4,6). There is also

an increased risk of low Apgar scores at 5 min (7),

encephalopathy (8) and admission to intensive care

(9) in post-term pregnancies, whereas no such

association has been observed for cerebral palsy

(10). At as early as 41 completed weeks an

increased risk of adverse neonatal outcomes has

Correspondence: Ulla-Britt Wennerholm, Department of Obstetrics and Gynecology, the Institute of Clinical Sciences, Sahlgrenska University Hospital, SE

416 85 Goteborg, Sweden. E-mail: [email protected]

Acta Obstetricia et Gynecologica. 2009; 88: 6�17

(Received 1 July 2008; accepted 26 September 2008)

ISSN 0001-6349 print/ISSN 1600-0412 online # 2009 Informa UK Ltd. (Informa Healthcare, Taylor & Francis AS)

DOI: 10.1080/00016340802555948

Acta Obstetricia et Gynecologica. 2009; 88: 6�17

(Received 1 July 2008; accepted 26 September 2008)

ISSN 0001-6349 print/ISSN 1600-0412 online # 2009 Informa UK Ltd. (Informa Healthcare, Taylor & Francis AS)

DOI: 10.1080/00016340802555948

been observed (5,6,11). The management of post-

term uncomplicated pregnancies is controversial.

Two major approaches have been employed: elec-

tive induction of labor at 41�42 weeks, and

expectant management with intermittent fetal mon-

itoring (e.g. cardiotocography, biophysical profile)

and selective induction of labor. These two man-

agements have been compared in randomized

controlled trials (RCT), and summarized and

evaluated in meta-analyses (Table I). According to

the most recent meta-analysis (12), significantly

lower perinatal mortality was found in the elective

induction arm, which has shifted practice in Europe

and North America (13) favoring elective induction

at 41�42 gestational weeks. However, most of the

RCTs included a limited number of women and

none of the RCTs was powered for evaluation of

perinatal mortality. Some of the studies were made

during the 1970s before the introduction of ultra-

sound dating, and some also included women who

were neither post-term nor close to post-term. The

studies utilized highly variable modes of fetal

surveillance in the expectant arm. Since the Co-

chrane review, another large, well-designed and

meticulously performed RCT (14) has been pub-

lished.

The aim of this study was to evaluate elective

induction of labor versus expectant management,

strictly including pregnancies of 41 weeks or beyond,

and including additional RCTs published after the

latest meta-analysis.

Material and methods

Search strategy/sources

We searched the PubMed, CINAHL, Cochrane

Database of Systematic Reviews, DARE and

PsycInfo databases for RCT and systematic reviews

published from 1980 to 19 November, 2007, using

the following words: (Meta-Analysis[ptyp] or Ran-

domised Controlled Trial[ptyp] or Controlled Clin-

ical Trial[ptyp]) and (induced labor or induction or

‘expectant management’) and (full-term pregnanc*

or full term pregnanc* or fullterm pregnanc* or

post-date deliver* or post date deliver* or postdate

deliver* or post-term pregnanc* or post term preg-

nanc*or postterm pregnanc* or prolonged preg-

nancy) and (perinatal death or fetal death or

intrauterine death or infant mortality or encephalo-

pathy or hypoxic-ischemic encephalopathy or cere-

bral palsy or meconium aspiration or Apgar or

attitudes or experiences or outcome).

The reference lists of identified studies were

searched manually.

Selection and validity assessment

RCTs and systematic reviews with induction of labor

at 41 weeks of gestation or more versus expectant

management were included. Studies published be-

fore 1980, when ultrasound dating was introduced,

were excluded, since this procedure changed the

precision in dating. We also excluded abstracts and

studies published in languages other than English,

assuming that the highest quality studies are pub-

lished as full articles and in English. We selected

trials assessing at least one of the following out-

comes: perinatal death, intrauterine fetal death, early

neonatal death, asphyxia, Apgar score B7 at 5 min,

meconium aspiration, admission to neonatal inten-

sive care unit, birthweight, cesarean section, assisted

vaginal delivery, perineal injury, postpartum hemor-

rhage and maternal satisfaction with the used

method.

Table I. Results from systematic reviews/meta-analyses comparing planned induction of labor at 41 weeks or later with expectant

management.

Myers et al. (AHRQ) (22).

Systematic review: 17

RCTs

Sanchez-Ramos et al. (23).

Meta-analysis: 16 RCTs;

OR; 95% CI

Gulmezoglu et al.* (12).


RR; 95% CI

Wennerholm et al. (43).**


RR; 95% CI

Perinatal death Favors labor induction 0.41; 0.14�1.18 0.30; 0.09�0.99 0.33; 0.10�1.09

Meconium aspiration

syndrome

No preference 0.46; 0.18�1.21 0.39; 0.21�0.75 0.43; 0.23�0.79

Cesarean delivery No preference 0.88; 0.78�0.99 41 weeks: 0.92; 0.76�1.12***;

42 weeks: 0.97; 0.72�1.31***

0.87; 0.80�0.96

*Seven studies (36�42) included in Gulmezoglu et al. (12) were excluded in Wennerholm et al. (43). Reasons for exclusions: interventions

before 41 weeks (36�38); published 1969 (39); published as abstracts (40,41); non-English language publication (42).

**One study (14) included in Wennerholm et al. (43) was not included in Gulmezoglu et al. (12).

***Pooled data for 41 and 42 weeks not available.

Induction of labor for post-date pregnancy 7

Validity of trials fulfilling inclusion criteria was

assessed using the JAMA validity score, the Swedish

Council on Technology Assessment in Health

Care (SBU) and the CONSORT checklist (15�18).

Criteria included external validity (eligibility, con-

secutive patients, patient number and reason for

non-participation, exclusion criteria clearly stated)

and internal validity (randomization procedure,

comparability of groups, blinding, compliance,

losses to follow-up, evaluation of outcome and side

effects, intention to treat) and precision (study

power). Quality rating was given for each study

according to SBU criteria, i.e. high, fair and poor.

Each reviewer independently assessed the validity of

included articles. Each article was assessed by at

least three reviewers. Two reviewers (UBW, CB)

extracted data. Disagreements were solved by dis-

cussion.

Potentially relevant titles identified after literature search (n= 69)

Titles excluded (n= 48) Inappropriate clinical question (trial of cervical ripening and not induction of labour, trial of two forms of induction of labour etc) (n=38) Data on pregnancies < 41 weeks (n=7) Non-English literature (n=1) Only published as abstracts (n=2)

Titles potentially appropriate (n=21) Titles excluded (n= 4) Alternate allocation trial (n=3) Quasi-randomised (n=1)

Articles with useful information (n=17) Randomised controlled trials included in meta-analysis (n=13, 14 articles) Systematic reviews (n=3)

Figure 1. Study selection process.

Figure 2. Labour induction versus expectant management at �41 weeks: Outcome: perinatal death.

8 U.-B. Wennerholm et al.

Analysis strategy

Statistical analyses were conducted using the Review

Manager Software (Rev Man 2003). We analyzed

categorical data using relative risks (RR) and 95%

confidence intervals (CI). For continuous outcomes,

we used weighted mean differences (WMD). We

assessed statistical heterogeneity between trials using

both the chi-squared test and the I2 statistic (19).

Where there was no statistical heterogeneity (p�0.1,

I2B25%), we pooled data using a fixed model.

Publication biases were checked using a funnel plot

(20). Subgroup analyses were performed for gesta-

tional age 41�0 and beyond and 42�0 and beyond,

respectively. Since management of induction differed

between the intervention and control group in the

largest study, the Canadian Multicenter Post-term

Pregnancy Trial (21), sensitivity analysis was carried

out excluding this trial. Ethical approval was not

required.

Results

Seventeen relevant publications were identified

(12,14,21�35). Three of these were systematic re-

views (12,22,23) and 14 were reports from RCTs

(14,21,24�35) (Tables I and II; Figure 1). Results

from one trial was reported in two publications

(14,29). Thus, results from 13 trials were used in

the meta-analyses. Excluded publications and rea-

sons for exclusion are given in Figure 1. In parti-

cular, articles included in the Cochrane review but

excluded in the present meta-analysis are specified in

Table I (36�42).

Descriptive data for each trial are presented in

Table II. Included trials were published between

1987 and 2007. The number of subjects in each trial

varied between 22 (32) and 3,418 (21).

Results are presented in Figures 2�12. A compar-

ison with previously performed meta-analyses is

presented in Table I.

Effects on perinatal mortality

There was no statistically significant difference in

perinatal deaths between the induction of labor and

expectant management groups (RR: 0.33, 95% CI:

0.10�1.09) (11 studies) (Figure 2). There was one

perinatal death in the induction of labor group and

eight in the expectant management group. There

were three perinatal deaths due to congenital

anomalies, one in the induction of labor and two in

the expectant management group. Of the eight

perinatal deaths observed in the expectant manage-

ment group, three were intrauterine fetal deaths

(Figure 3) and five occurred in the first seven days

of life (Figure 4). The perinatal death in the

induction of labor group occurred in the first seven

days of life.

Effects on other perinatal outcomes

Induction of labor was associated with fewer infants

with meconium aspiration syndrome compared with

expectant management (RR: 0.43; 95% CI: 0.23�0.79) (seven studies; Figure 5). There were no

significant differences in newborns with birth as-

phyxia (two studies; Figure 6), low Apgar scores (B7

at 5 min) (nine studies; Figure 7) or in intensive

care unit admissions (eight studies; Figure 8) be-

tween induction of labor or expectant management

groups. Newborns in the induction of labor group

had lower mean birthweight (WMD: �44.41; 95%

CI: �79.37 to �9.45) (eight studies; Figure 9).

Effects on cesarean delivery and assisted vaginal delivery

All 13 trials reported on cesarean deliveries. Women

in the induction of labor group were less likely to

have undergone a cesarean section than women in

the expectant management group (RR: 0.87; 95%

CI: 0.80�0.96) (Figure 10). Seven trials reported on

assisted vaginal delivery. There was no statistical

difference in the risk of assisted vaginal delivery

(Figure 11). When performing a sensitivity analysis

after excluding the Canadian Multicenter Post-term

Pregnancy Trial (21), no significant difference was

found for cesarean delivery rates between the two

groups (RR: 0.88; CI: 0.77�1.01).

Maternal complications and potential benefits

A few studies reported on maternal complications

such as postpartum hemorrhage, perineal trauma

and endometritis. No significant differences were

found for any of these maternal complications. Most

studies did not report individual data, making it

impossible to perform a meta-analysis on maternal

complications. Only one trial measured maternal

satisfaction. Maternal satisfaction was statistically

significantly higher in the induction of labor group

(Figure 12).

Subgroup analysis

In the 41-week group, induction of labor signifi-

cantly reduced the risk of meconium aspiration

syndrome (RR: 0.35; CI: 0.16�0.75) (five trials;

Figure 5). Women in the 41-week group whose labor

was induced were less likely to have undergone a


Table II. Characteristics of included randomized controlled trials and quality rating.

Trial, year Country No. of women

Definition of

post-date (d) Methods of induction Monitoring of control group

Quality

rating

Augensen, 1987 (24) Norway 409 290 Oxytocin infusion and amniotomy NST twice weekly Poor

Bergsjo, 1989 (25) China 188 294 Membrane stripping, oxytocin infusion

and amniotomy

Fetal kick counts, atropine test,

ultrasound and urinary estriol

Poor

Chanrachakul, 2003 (26) Thailand 249 290 Amniotomy and oxytocin infusion NST and AFI once weekly, twice

weekly after 43 weeks

Poor

Dyson, 1987 (27) USA 302 287 PGE2 gel intravaginally (3 mg) or PGE2

gel (0.5 mg) intracervically; and oxytocin

infusion with amniotomy

NST twice weekly, AFI weekly

between 41 and 42 weeks and twice

weekly after 42 weeks

Poor

Gelisen, 2005 (28) Turkey 600 287 Misoprostol 50 mg intravaginally every 6

h�3 and amniotomy and oxytocin infusion

or oxytocin infusion or Foley catheter with

balloon above the internal cervical os filled

with 50 ml saline and oxytocin infusion

NST and AFI twice weekly and BPP

once 3�5 days after randomization

Poor

Hannah, 1992 (21) Canada 3407 287 PGE2 gel (0.5 mg) intracervically, every 6

h�3 and/or oxytocin infusion/amniotomy

or both

Fetal kick counts daily, NST three

times weekly and AFI two to three

times weekly

Fair

Heimstad, 2007a,b (14,29) Norway 508 289 Misoprostol 50 ug intravaginally every 6 h or

PGE2 gel (0.5 mg) intracervically every 12 h

during 2 days or amniotomy and oxytocin

infusion

AFI, and NST every third day Fair

Herabutya, 1992 (30) Thailand 108 294 PGE2 gel (0.5 mg) intracervically every 6 h

and maximum three times, and amniotomy/

oxytocin or both

NST once weekly and twice weekly

after 43 weeks

Poor

James, 2001 (31) India 74 287 Extra-amniotically placed Foley catheter

with balloon filled with 20 ml saline if

Bishop score B5; if �5 membrane

stripping, after 12 h amniotomy, and

oxytocin infusion

Fetal kick counts daily and BPP on

alternate days

Poor

Martin, 1989 (32) USA 22 287 Laminaria tents and oxytocin infusion NST and AFI weekly Poor

NICHHD, 1994 (33) USA 440 287 PGE2 (0.5 mg) or placebo gel intracervically,

amniotomy and oxytocin infusion

NST and AFI twice weekly Fair

Roach, 1997 (34) Hong Kong 201 294 PGE2 pessaries (3 mg) vaginally every 6 h NST twice weekly and AFI once

weekly

Poor

Witter, 1987 (35) USA 200 294 Oxytocin and amniotomy Urinary estriol twice a week and

three times a week after 43 weeks

Poor

NST, non-stress test; AFI, amniotic fluid index; PGE2, prostaglandin E2; BPP, biophysical profile.

10

U.-B

.W

ennerh

olmet

al.

cesarean section than women with expectant

management (RR: 0.87; CI: 0.79�0.96) (nine trials;

Figure 10). Newborns in the 42-week induction

of labor group had lower mean birthweight (WMD

�101.58; 95% CI: �179.01 to �24.15) (three

studies; Figure 9). The gestational age subgroup

analysis did not show any other significant differ-

ences.

Figure 3. Labour induction versus expectant management at �41weeks. Outcome Intrauterine fetal death.

Figure 4. Labour induction versus expectant management at �41weeks. Outcome Early neonatal death (B7 days).


Discussion

The main finding in this meta-analysis is that there is

no significant difference in perinatal mortality be-

tween induction of labor at 41 weeks’ gestation or

later as compared to expectant management. These

results differ from the recent review by Gulmezoglu

et al. published in the Cochrane Collaboration (12),

where significantly lower perinatal mortality for

elective induction in pregnancies beyond 37 weeks

was found, however close to unity (RR: 0.30; 95%

CI: 0.09�0.99). Our results differ from that review

because of different selection criteria for the in-

cluded trials. We regarded it as more appropriate to

include only studies of 41 weeks or beyond, i.e. a

point in time where perinatal problems are known to

increase (5,6,11), since this is where discussion

about induction is focused today. We also excluded

two studies (40,41) published only as abstracts, one

study not published in English (42) and one study

published in 1969 (39) (Table I). These exclusions

fulfilled our exclusion criteria determined in advance

for this systematic review.

In our meta-analysis, no individual study reached

a level of high quality concerning validity and

precision, and only three trials (14,21,33) reached

a level of fair quality. Most studies were assessed as

being of poor quality, in spite of a randomized

design. This meta-analysis demonstrates the pro-

blems that arise when the primary outcome is a rare

event. A total of nine perinatal deaths occurred

among 6,617 newborns. Some studies included

perinatal deaths where the child had a severe

congenital malformation, while other studies ex-

cluded these newborns. It is clear that an additional

few perinatal deaths in either group may reverse the

risk. It can be noted that observations from a large

registry study from Sweden (4) indicated an in-

creased risk for stillbirth with gestational age for

primiparous but not for multiparous women. No

Figure 5. Labour induction versus expectant management at �41weeks: Outcome Meconium aspiration.

Figure 6. Labour induction versus expectant management at �41weeks: Outcome Asphyxia.


subgroup analysis for parity was performed in the

studies included in this systematic review depending

on the limited number of perinatal deaths.

In this meta-analysis, we also found that induction

of labor compared with expectant management was

associated with a significantly lower risk of meco-

nium aspiration syndrome. However, meconium

aspiration syndrome is a poor indicator of neonatal

stress, and most newborns with meconium aspira-

tion syndrome recover and remain healthy.

The finding that the cesarean delivery rate was

significantly lower in the induction group might be

unexpected. In the largest trial in this meta-analysis,

the Canadian Multicenter Post-term Pregnancy

Trial (21), a significantly lower cesarean delivery

rate was also seen in the induction group, probably

Figure 7. Labour induction versus expectant management at �41weeks: Outcome Apgar score B7 at 5 min.

Figure 8. Labour induction versus expectant management at �41weeks: Outcome Admission to neonatal intensive care unit.


owing to different types of management of pregnan-

cies in the two groups, as discussed by the authors.

No prostaglandin was used in the expectant manage-

ment group. When we did a sensitivity analysis from

which the Canadian trial was excluded, a significant

difference in cesarean delivery rates between the two

groups was no longer detected.

Only one recent study investigated maternal

satisfaction (29). Women preferred induction of

labor to serial antenatal monitoring beyond 41 weeks

(74 vs 38% of the women said they would prefer the

same management in a subsequent pregnancy).

The main strength of this study was the restriction

to trials that only included pregnancies of 41 weeks

or more, which is a time point where neonatal

problems are known to arise. The weaknesses of

our conclusions are closely linked with the weak-

nesses of the individual trials, e.g. the poor quality of

Figure 9. Labour induction versus expectant management at �41weeks: Outcome: Birth weight.

Figure 10. Labour induction versus expectant management at �41weeks: Outcome: Caesarean section.


most of the studies included, owing to shortcomings

in external and internal validity and small sample

sizes.

In conclusion, the present meta-analysis did not

demonstrate that there is a significant difference in

perinatal mortality when comparing a strategy of

elective induction with one of expectant manage-

ment. A change in attitudes encouraging more

induction may therefore be questionable from a

scientific point of view when the aim is to offer

women treatment according to the best available

evidence. Since no particular management has been

found to be superior from a medical point of view, a

strategy involving either induction or active expecta-

tion could be regarded as relevant and with possibi-

lities for individualization. The number of women

reaching 41 weeks is quite substantial. A change in

policy encouraging induction of labor would require

a huge increase in resources in the delivery wards.

Before advocating such a change in management,

the possibility of performing an adequately powered

randomized trial should be discussed.

Acknowledgements

We thank Anders Flisberg, Lars Ladfors, Therese

Svanberg, Margareta Wennergren and Anna Wess-

berg for their contributions. The study was funded

by grants from Sahlgrenska University Hospital.

Declaration of interest: The authors report no

conflicts of interest. The authors alone are respon-

sible for the content and writing of the paper.

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Figure 11. Labour induction versus expectant management at �41weeks: Outcome: Assisted vaginal delivery.

Figure 12. Labour induction versus expectant management at �41weeks: Outcome: Maternal satisfaction.


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