最新研究揭示:双胞胎最佳分娩时间是37周
2016/09/10
最新研究发现,对于双卵双胎孕妇而言,最佳分娩时间应该是在妊娠的第37周,因为这个时间段胎儿出生会降低发生死胎、减少新生儿死亡的风险。而对于共享一个胎盘的双胞胎,分娩的时间应该在第36周。


我们常说的双胞胎,即双胎妊娠,可分为两种情况:一种是一次排出两个卵子并分别受精后发育成两个胚胎,即双卵双胎,约占双胎妊娠的70%,均为双绒毛膜双胎,两个胎儿各有各自的胎盘;另一种是由一个受精卵分裂形成的两个胚胎,约占双胎的30%,性别均相同,约有1/3(10%)为双绒毛膜双胎,2/3(20%)为单绒毛膜双胎。

与单胎妊娠相比,双胎发生死胎以及新生儿死亡的风险会相对较高。为了降低这种风险,双胞胎孕妇常常需要提前分娩。

然而,几乎没有科学证据去表明双胞胎最佳的出生时间。而且,医生对此观点也不尽相同,对于共享同一胎盘的双胞胎(单绒毛膜双胎),大家建议的分娩时间范围是34—37周,对于两个胎盘的双卵双胎(双绒毛膜双胎),他们认为分娩时间应该在37—39周内。

为了解决这一问题,来自于伦敦玛丽女王大学的研究团队筛查了针对双胞胎妊娠的32篇学术文章,对其中的数据进行汇总分析。这十年间发表的32篇文章共调研了35,171例双胞胎孕妇(29,685例双绒毛膜双胎、5,486单绒毛膜双胎)。相关研究成果发表于《BMJ》期刊。

妊娠周期对发生死胎、新生儿死亡的影响

研究人员选择分娩周期、死胎和新生儿死亡率作为分析指标,以便评估 “孕妇观察等待”与“发生死胎”以及“34周后出生”与“新生儿死亡率”之间的关联性,并希望找到降低风险的最佳时间点。

结果发现,对于双绒毛膜双胎而言,降低死胎、新生儿死亡风险的最佳妊娠周期是37周。如果延迟1周,即38周分娩,发生死胎的概率会上涨8.8‰。

对于单绒毛膜双胎,这种风险的增加发生在36周以后,但是,对于这一类别的双胞胎,研究人员表示,最佳出生时间还需要更多的研究数据才能够确定。

研究人员强调,实际的死胎风险或许高出预估值。他们的研究全面预估了不同妊娠周期、分娩时间对于双绒毛膜双胎发生死胎、新生儿死亡的风险影响,为双胞胎孕妇及相关医护人员提供了参考信息,以便他们规划合适的分娩时间。

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  • Prospective risk of stillbirth and neonatal complications in twin pregnancies: systematic review and meta-analysis

    Results 32 studies (29 685 dichorionic, 5486 monochorionic pregnancies) were included. In dichorionic twin pregnancies beyond 34 weeks (15 studies, 17 830 pregnancies), the prospective weekly risk of stillbirths from expectant management and the risk of neonatal death from delivery were balanced at 37 weeks’ gestation (risk difference 1.2/1000, 95% confidence interval −1.3 to 3.6; I2=0%). Delay in delivery by a week (to 38 weeks) led to an additional 8.8 perinatal deaths per 1000 pregnancies (95% confidence interval 3.6 to 14.0/1000; I2=0%) compared with the previous week. In monochorionic pregnancies beyond 34 weeks (13 studies, 2149 pregnancies), there was a trend towards an increase in stillbirths compared with neonatal deaths after 36 weeks, with an additional 2.5 per 1000 perinatal deaths, which was not significant (−12.4 to 17.4/1000; I2=0%). The rates of neonatal morbidity showed a consistent reduction with increasing gestational age in monochorionic and dichorionic pregnancies, and admission to the neonatal intensive care unit was the commonest neonatal complication. The actual risk of stillbirth near term might be higher than reported estimates because of the policy of planned delivery in twin pregnancies. Conclusions To minimise perinatal deaths, in uncomplicated dichorionic twin pregnancies delivery should be considered at 37 weeks’ gestation; in monochorionic pregnancies delivery should be considered at 36 weeks.

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