Background

A recent randomised controlled trial (RCT) demonstrated that induction of labour at 39 weeks of gestational age has no short-term adverse effect on the mother or infant among nulliparous women aged ≥35 years. However, the trial was underpowered to address the effect of routine induction of labour on the risk of perinatal death. We aimed to determine the association between induction of labour at ≥39 weeks and the risk of perinatal mortality among nulliparous women aged ≥35 years.

Methods and findings

We used English Hospital Episode Statistics (HES) data collected between April 2009 and March 2014 to compare perinatal mortality between induction of labour at 39, 40, and 41 weeks of gestation and expectant management (continuation of pregnancy to either spontaneous labour, induction of labour, or caesarean section at a later gestation). Analysis was by multivariable Poisson regression with adjustment for maternal characteristics and pregnancy-related conditions. Among the cohort of 77,327 nulliparous women aged 35 to 50 years delivering a singleton infant, 33.1% had labour induced: these women tended to be older and more likely to have medical complications of pregnancy, and the infants were more likely to be small for gestational age.

Induction of labour at 40 weeks (compared with expectant management) was associated with a lower risk of in-hospital perinatal death (0.08% versus 0.26%; adjusted risk ratio [adjRR] 0.33; 95% CI 0.13–0.80, P = 0.015) and meconium aspiration syndrome (0.44% versus 0.86%; adjRR 0.52; 95% CI 0.35–0.78, P = 0.002). Induction at 40 weeks was also associated with a slightly increased risk of instrumental vaginal delivery (adjRR 1.06; 95% CI 1.01–1.11, P = 0.020) and emergency caesarean section (adjRR 1.05; 95% CI 1.01–1.09, P = 0.019). The number needed to treat (NNT) analysis indicated that 562 (95% CI 366–1,210) inductions of labour at 40 weeks would be required to prevent 1 perinatal death. Limitations of the study include the reliance on observational data in which gestational age is recorded in weeks rather than days. There is also the potential for unmeasured confounders and under-recording of induction of labour or perinatal death in the dataset.

Conclusions

Bringing forward the routine offer of induction of labour from the current recommendation of 41–42 weeks to 40 weeks of gestation in nulliparous women aged ≥35 years may reduce overall rates of perinatal death.

中文翻译：

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35 岁或以上未产妇的围产期死亡率与引产与期待治疗相关：一项英国全国队列研究

背景

最近的一项随机对照试验（RCT）表明，对于年龄≥35岁的未生育妇女，孕39周引产对母亲或婴儿没有短期不良影响。然而，该试验不足以解决常规引产对围产儿死亡风险的影响。我们的目的是确定年龄≥35岁的未产妇中≥39周的引产与围产期死亡风险之间的关系。

方法和结果

我们使用 2009 年 4 月至 2014 年 3 月期间收集的英国医院发作统计 (HES) 数据来比较妊娠 39、40 和 41 周引产与期待治疗（继续妊娠至自然分娩、引产）之间的围产期死亡率。 ，或妊娠后期的剖腹产）。通过多变量泊松回归进行分析，并调整母亲特征和妊娠相关条件。在 77,327 名 35 至 50 岁的未产妇生下单胎婴儿的队列中，33.1% 接受过引产：这些妇女往往年龄较大，更容易出现妊娠并发症，而且婴儿更可能小于妊娠期年龄。

40 周引产（与期待治疗相比）与院内围产儿死亡风险较低相关（0.08% 对比 0.26%；调整后风险比 [adjRR] 0.33；95% CI 0.13–0.80，P = 0.015）胎粪吸入综合征（0.44% vs 0.86%；adjRR 0.52；95% CI 0.35–0.78，P = 0.002）。40 周引产还与阴道助产（adjRR 1.06；95% CI 1.01–1.11，P = 0.020）和紧急剖腹产（adjRR 1.05；95% CI 1.01–1.09，P = 0.019）风险略有增加相关。 。需要治疗的数量 (NNT) 分析表明，需要 562 次 (95% CI 366–1,210) 40 周引产才能预防 1 例围产儿死亡。该研究的局限性包括依赖观察数据，其中胎龄以周而不是天为单位记录。数据集中还可能存在未测量的混杂因素以及引产或围产期死亡的记录不足。

结论

对于年龄≥35 岁的未产妇，将常规引产从目前建议的妊娠期 41-42 周提前至 40 周可能会降低围产期死亡率。