Keulen Judit K J, Bruinsma Aafke, Kortekaas Joep C, van Dillen Jeroen, van der Post Joris A M, de Miranda Esteriek
Department of Obstetrics and Gynaecology, Amsterdam UMC, University of Amsterdam, Meibergdreef 9, Amsterdam, The Netherlands.
Department of Obstetrics and Gynaecology, Amsterdam UMC, University of Amsterdam, Meibergdreef 9, Amsterdam, The Netherlands.
Midwifery. 2018 Nov;66:111-118. doi: 10.1016/j.midw.2018.07.011. Epub 2018 Aug 11.
Postterm pregnancy is associated with increased perinatal risk. The WHO defines postterm pregnancy as a pregnancy at or beyond 42 weeks + 0 days, though currently labour is induced at 41 weeks in many settings. Guidelines on timing of labour induction are frequently based on the Cochrane systematic review 'Induction of labour for improving birth outcomes for women at or beyond term' in which is concluded that a policy of induction of labour is associated with fewer adverse perinatal outcome and fewer Caesarean sections. However, the included trials differed regarding the timing of induction, ranging from 39 to beyond 42 weeks while the upper limit of expectant management exceeded a gestational age of 42 weeks in most studies.
to evaluate perinatal mortality, meconium aspiration syndrome and Caesarean section rate of trials comparing a policy of elective induction of labour and expectant management according to timeframes of comparison with a focus on studies within the 41-42 weeks' timeframe.
Review.
The systematic review of Cochrane was used as a starting point for assessing relevant trials and a search was performed for additional recent trials. We evaluated incidence and causes of perinatal mortality, incidence of meconium aspiration syndrome and Caesarean section according to three time frames of comparison. We pooled estimates and heterogeneity was tested. The quality of the included trials was assessed using the Quality Assessment Tool for Quantative Studies (EPHPP).
In total 22 trials were included which had all different timeframes of comparison. Only one trial compared induction of labour at 41 weeks + 0-2 days with induction at 42 weeks + 0 days, three other trials compared induction of labour at 41 weeks + 0-6 days with induction at 42 weeks + 0-6 days. In 18 trials the comparison was outside the 41-42 weeks' timeframe: in six trials induction was planned ≤ 40 weeks and in another 12 trials expectant management was beyond 43 weeks. The incidence of potentially gestational age associated perinatal mortality between 41 and 42 weeks was 0/2.444 [0%] (induction) versus 4/2.452 [0.16%] (expectant management), NNT 613; 95%CI 613 - infinite. Two trials in the timeframe of comparison 41-42 weeks were available for evaluation of meconium aspiration syndrome (6/554 (induction) versus 14/554 (expectant management), RR 0.44; 95%CI 0.17-1.16). Three trials in the timeframe 41-42 weeks could be evaluated for Caesarean section, with different inclusion criteria regarding Bishop score. There was no significant difference in the Caesarean section rate 93/629 (induction) versus 106/629 (expectant management), RR 0.88; 95%CI 0.68-1.13.
Evidence is lacking for the recommendation to induce labour at 41 weeks instead of 42 weeks for the improvement of perinatal outcome. More studies comparing both timeframes with an adequate sample size are needed to establish the optimal timing of induction of labour in late-term pregnancies.
过期妊娠与围产期风险增加相关。世界卫生组织将过期妊娠定义为妊娠达到或超过42周+0天，不过目前在许多情况下，在41周时就会引产。引产时机的指南通常基于Cochrane系统评价“引产以改善足月及过期妊娠妇女的分娩结局”，该评价得出结论，引产政策与较少的不良围产期结局及较少的剖宫产相关。然而，纳入的试验在引产时机方面存在差异，范围从39周至超过42周，而在大多数研究中，期待管理的上限超过了42周的孕周。
根据比较时间框架，评估比较择期引产政策与期待管理的试验的围产期死亡率、胎粪吸入综合征和剖宫产率，重点关注41 - 42周时间框架内的研究。
综述。
以Cochrane系统评价作为评估相关试验的起点，并搜索近期的其他试验。我们根据三个比较时间框架评估围产期死亡率的发生率和原因、胎粪吸入综合征的发生率以及剖宫产情况。我们汇总估计值并检验异质性。使用定量研究质量评估工具（EPHPP）评估纳入试验的质量。
共纳入22项试验，其比较时间框架各不相同。只有一项试验比较了41周+0 - 2天引产与42周+0天引产，另外三项试验比较了41周+0 - 6天引产与42周+0 - 6天引产。在18项试验中，比较超出了41 - 42周时间框架：在6项试验中，计划引产≤40周，在另外12项试验中，期待管理超过43周。41至42周之间潜在与孕周相关的围产期死亡率发生率为0/2444[0%]（引产）对4/2,452[0.16%]（期待管理），需治疗人数613；95%置信区间613 - ∞。在41 - 42周比较时间框架内有两项试验可用于评估胎粪吸入综合征（6/554（引产）对14/554（期待管理），相对危险度0.44；95%置信区间0.17 - 1.16）。在41 - 42周时间框架内有三项试验可用于评估剖宫产情况，关于 Bishop评分的纳入标准不同。剖宫产率无显著差异，93/629（引产）对106/629（期待管理），相对危险度0.88；95%置信区间0.68 - 1.13。
缺乏证据支持在41周而非42周引产以改善围产期结局的建议。需要更多比较这两个时间框架且样本量充足的研究，以确定晚期妊娠引产的最佳时机。
