Induction of labour for improving birth outcomes for women at or beyond term

  • Review
  • Intervention

Authors

  • Philippa Middleton,

    Corresponding author
    1. Healthy Mothers, Babies and Children, South Australian Health and Medical Research Institute, Adelaide, South Australia, Australia
    • Philippa Middleton, Healthy Mothers, Babies and Children, South Australian Health and Medical Research Institute, Women's and Children's Hospital, 72 King William Road, Adelaide, South Australia, 5006, Australia. philippa.middleton@adelaide.edu.au. mpm@ozemail.com.au.

  • Emily Shepherd,

    1. The University of Adelaide, ARCH: Australian Research Centre for Health of Women and Babies, Robinson Research Institute, Discipline of Obstetrics and Gynaecology, Adelaide, South Australia, Australia
  • Caroline A Crowther

    1. The University of Auckland, Liggins Institute, Auckland, New Zealand

Abstract

Background

Beyond term, the risks of stillbirth or neonatal death increase. It is unclear whether a policy of labour induction can reduce these risks. This Cochrane review is an update of a review that was originally published in 2006 and subsequently updated in 2012

Objectives

To assess the effects of a policy of labour induction at or beyond term compared with a policy of awaiting spontaneous labour or until an indication for birth induction of labour is identified) on pregnancy outcomes for infant and mother.

Search methods

We searched Cochrane Pregnancy and Childbirth’s Trials Register, ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform (ICTRP) (9 October 2017), and reference lists of retrieved studies.

Selection criteria

Randomised controlled trials (RCTs) conducted in pregnant women at or beyond term, comparing a policy of labour induction with a policy of awaiting spontaneous onset of labour (expectant management). We also included trials published in abstract form only. Cluster-RCTs, quasi-RCTs and trials using a cross-over design are not eligible for inclusion in this review.

We included pregnant women at or beyond term. Since a risk factor at this stage of pregnancy would normally require an intervention, only trials including women at low risk for complications were eligible. We accepted the trialists' definition of 'low risk'. The trials of induction of labour in women with prelabour rupture of membranes at or beyond term were not considered in this review but are considered in a separate Cochrane review.

Data collection and analysis

Two reviewers independently assessed trials for inclusion, assessed risk of bias and extracted data. Data were checked for accuracy. We assessed the quality of evidence using the GRADE approach.

Main results

In this updated review, we included 30 RCTs (reporting on 12,479 women). The trials took place in Norway, China, Thailand, the USA, Austria, Turkey, Canada, UK, India, Tunisia, Finland, Spain, Sweden and the Netherlands. They were generally at a moderate risk of bias.

Compared with a policy of expectant management, a policy of labour induction was associated with fewer (all-cause) perinatal deaths (risk ratio (RR) 0.33, 95% confidence interval (CI) 0.14 to 0.78; 20 trials, 9960 infants; moderate-quality evidence). There were two perinatal deaths in the labour induction policy group compared with 16 perinatal deaths in the expectant management group. The number needed to treat to for an additional beneficial outcome (NNTB) with induction of labour in order to prevent one perinatal death was 426 (95% CI 338 to 1337). There were fewer stillbirths in the induction group (RR 0.33, 95% CI 0.11 to 0.96; 20 trials, 9960 infants; moderate-quality evidence); there was one stillbirth in the induction policy arm and 10 in the expectant management group.

For women in the policy of induction arms of trials, there were fewer caesarean sections compared with expectant management (RR 0.92, 95% CI 0.85 to 0.99; 27 trials, 11,738 women; moderate-quality evidence); and a corresponding marginal increase in operative vaginal births with induction (RR 1.07, 95% CI 0.99 to 1.16; 18 trials, 9281 women; moderate-quality evidence). There was no evidence of a difference between groups for perineal trauma (RR 1.09, 95% CI 0.65 to 1.83; 4 trials; 3028 women; low-quality evidence), postpartum haemorrhage (RR 1.09 95% CI 0.92 to 1.30, 5 trials; 3315 women; low-quality evidence), or length of maternal hospital stay (average mean difference (MD) -0.34 days, 95% CI -1.00 to 0.33; 5 trials; 1146 women; Tau² = 0.49; I² 95%; very low-quality evidence).

Rates of neonatal intensive care unit (NICU) admission were lower (RR 0.88, 95% CI 0.77 to 1.01; 13 trials, 8531 infants; moderate-quality evidence) and fewer babies had Apgar scores less than seven at five minutes in the induction groups compared with expectant management (RR 0.70, 95% CI 0.50 to 0.98; 16 trials, 9047 infants; moderate-quality evidence).

There was no evidence of a difference for neonatal trauma (RR 1.18, 95% CI 0.68 to 2.05; 3 trials, 4255 infants; low-quality evidence), for induction compared with expectant management.

Neonatal encephalopathy, neurodevelopment at childhood follow-up, breastfeeding at discharge and postnatal depression were not reported by any trials.

In subgroup analyses, no clear differences between timing of induction (< 41 weeks versus ≥ 41 weeks' gestation) or by state of cervix were seen for perinatal death, stillbirth, NICU admission, caesarean section, or perineal trauma. However, operative vaginal birth was more common in the inductions at < 41 weeks' gestation subgroup compared with inductions at later gestational ages. The majority of trials (about 75% of participants) adopted a policy of induction at ≥ 41 weeks (> 287 days) gestation for the intervention arm.

Authors' conclusions

A policy of labour induction at or beyond term compared with expectant management is associated with fewer perinatal deaths and fewer caesarean sections; but more operative vaginal births. NICU admissions were lower and fewer babies had low Apgar scores with induction. No important differences were seen for most of the other maternal and infant outcomes.

Most of the important outcomes assessed using GRADE had a rating of moderate or low-quality evidence - with downgrading decisions generally due to study limitations such as lack of blinding (a condition inherent in comparisons between a policy of acting and of waiting), or imprecise effect estimates. One outcome (length of maternal stay) was downgraded further to very low-quality evidence due to inconsistency.

Although the absolute risk of perinatal death is small, it may be helpful to offer women appropriate counselling to help choose between scheduled induction for a post-term pregnancy or monitoring without (or later) induction).

The optimal timing of offering induction of labour to women at or beyond term warrants further investigation, as does further exploration of risk profiles of women and their values and preferences. Individual participant meta-analysis is likely to help elucidate the role of factors, such as parity, in influencing outcomes of induction compared with expectant management.

Plain language summary

Induction of labour in women with normal pregnancies at or beyond term

What is the issue?

A normal pregnancy lasts about 40 weeks from the start of the woman's last menstrual period, but anything from 37 to 42 weeks is considered as being at term (within the normal range). If a pregnancy goes too long, a woman and her clinician may wish to intervene to bring the birth on, for example, by induction.

Why is this important?

Births after 42 weeks' gestation may slightly increase risks for babies, including a greater risk of death (before or shortly after birth). However induction of labour may also have risks for mothers and their babies, especially if women are not ready to labour. No tests can predict if babies would be better to stay inside their mother or if labour should be induced to make the birth happen sooner. Many hospitals therefore have policies for how long pregnancies should continue. This update (originally published in 2006 and subsequently updated in 2012) looks to see if inducing labour at a set time at or beyond term, could reduce risks for the babies.

What evidence did we find?

We searched for evidence up 9 October 2017 and identified 30 trials with over 12,000 women. The trials took place in Norway, China, Thailand, the USA, Austria, Turkey, Canada, UK, India, Tunisia, Finland, Spain, Sweden and the Netherlands. The evidence was mostly of moderate quality. The trials compared a policy to induce labour at or later than term (usually after 41 completed weeks of gestation (> 287 days)) with waiting for labour to start and/or waiting for a period before inducing labour.

We found that there were fewer deaths of babies in hospitals with a policy to induce when a pregnancy was continuing beyond term (moderate-quality evidence). Fewer caesarean births were required with induction compared with waiting, but more assisted vaginal births were required with induction. There were fewer admissions to the intensive care nursery and fewer low Apgar scores at five minutes after birth (a simple test to test babies' health) in the induction groups compared with waiting (moderate-quality evidence). We found that there were no clear differences between a policy to induce at or later than term or waiting in the risks of mothers having trauma to their perineum or bleeding after birth (both low-quality evidence), in the length of their hospital stay (very-low quality evidence), or in their babies having trauma (low-quality evidence), None of the trials provided information on breastfeeding at discharge from hospital, postnatal depression, or whether the babies had encephalopathy (early abnormal neurological function), or child development.

What does this mean?

A policy of labour induction compared with expectant management is associated with fewer deaths of babies and fewer caesarean sections; but more assisted vaginal births. Although the chances of babies dying are small, it may help to offer women appropriate counselling to make an informed choice between induction of labour for pregnancies at, or later than, term - or waiting for labour to start and/or waiting before inducing labour.

The best time to offer induction of labour to women at or beyond term is not yet clear and warrants further investigation. The risk profiles of women as well as their values and preferences could also be considered.

平易な要約

正期産期以降の正常妊娠の女性の分娩誘発

論点

正常な妊娠は女性の最後の月経の開始から約 40 週続き、妊娠37 ~42 週の期間は正期産(正常範囲内) とみなされる。妊娠期間が長くなると、女性や担当の臨床医は、分娩誘発など、分娩に至るための介入を考慮するかもしれない。

重要である理由

妊娠 42 週以降の出産は、より高い死亡の発生(出生前、または出生直後) を含む、児のリスクを高める可能性がある。しかしながら、特に分娩準備が整っていない場合は、分娩誘発も母児へのリスクがある。児が母体内に留まっていた方がよいか、すぐに出産となるよう分娩が誘発されるべきか、どちらが児にとって良いのかを予測できる検査はない。したがって、多くの病院では、妊娠期間はどのくらい継続させるべきなのかという方針を適用する。このアップデート版(2006年に最初に出版され、その後2012年に更新)は、正期産以降の分娩誘発は児へのリスクを減らすことができるかどうかを検討する。

どのようなエビデンスが得られたか?

2017 年 10 月 9 日までのエビデンスを検索をし、12,000 人以上を含む 30 試験を同定した。試験は、ノルウェー、中国、タイ、米国、オーストリア、トルコ、カナダ、英国、インド、チュニジア、フィンランド、スペイン、スウェーデン、オランダで行われた。このエビデンスの質はおおむね中等度だった。試験は、正期産期またはそれ以降(通常妊娠 41 週以降 (> 287 日))の分娩誘発と、自然な陣痛発来を待機、もしくは、分娩誘発開始前のある一定期間待機する方針を比較していた。

正期産期以降も妊娠継続している場合、分娩誘発を行う方針の病院での児の死亡が少ないことが分かった (中等度の質のエビデンス) 。待機と比較して分娩誘発の方が、帝王切開での出産は少なかったが、器械分娩は多かった。待機と比較して、誘発を行ったグループでは、新生児集中治療室入室は少なく、出生5分後のアプガースコア (児の健康状態を評価する簡単なテスト) は低かった (中等度の質のエビデンス) 。正期産期またはそれ以降に分娩誘発を行うか、待機するかという方針について、会陰裂傷や分娩後の出血の発生(低度の質のエビデンス)、入院期間(非常に低度の質のエビデンス)、児の外傷(低度の質のエビデンス)について、明確な差はなかった。病院から退院時の母乳育児や、産後うつ、児の脳症 (早期神経機能異常)、や小児の発達については、どの試験にも記載はなかった。

意味するもの

待機的な管理と比較して、分娩誘発の方針は、児の死亡や帝王切開の減少との関連がみられたが、器械分娩は増加していた。児が死亡する可能性は小さいが、適切なカウンセリングを提供することで、正期産期またはそれ以降に分娩誘発を行うか、分娩開始を待機または、分娩誘発を開始するまである一定期間待機することについて、女性のインフォームドチョイスを支援できる。

正期産期またはそれ以降の女性に対し、いつ分娩誘発を行うことが最も良い時期なのかについては、まだ明確でなく、さらなる調査が必要である。リスクの内容と同様に、女性の価値観や希望も考慮すべきである。

訳注

《実施組織》増澤祐子、杉山伸子 翻訳[2018.5.27] 《注意》この日本語訳は、臨床医、疫学研究者などによる翻訳のチェックを受けて公開していますが、訳語の間違いなどお気づきの点がございましたら、コクランジャパンまでご連絡ください。なお、2013年6月からコクラン・ライブラリーのNew review, Updated reviewとも日単位で更新されています。最新版の日本語訳を掲載するよう努めておりますが、タイム・ラグが生じている場合もあります。ご利用に際しては、最新版(英語版)の内容をご確認ください。   《CD004945》