Ammon Avalos Lyndsay, Galindo Claudia, Li De-Kun
Division of Research, Kaiser Permanente, Oakland, California, USA.
Birth Defects Res A Clin Mol Teratol. 2012 Jun;94(6):417-23. doi: 10.1002/bdra.23014. Epub 2012 Apr 18.
The objectives of the current study were to calculate: (1) the expected rates of miscarriage by gestational week; (2) the cumulative risk of miscarriage; and (3) the remaining risk of miscarriage for gestational weeks five through 20, through a systematic review of the literature. We searched MEDLINE for articles published in English through the end of 2009. References of articles were also searched. Four studies were identified to have the three necessary pieces of information for the proposed calculations: (1) gestational age at study entry, (2) pregnancy outcome; and (3) the gestational age at which the pregnancy outcome occurred. Data were extracted from each study and Life Table Analysis Methods were conducted. Weekly miscarriage rates varied in the early gestational weeks with the highest rate documented at >20 miscarriages per 1000 women-weeks at each week of gestation prior to week 13. By week 14, the rate for all studies became relatively comparable and fell below 10 miscarriages per 1000 woman-weeks at risk and fell even lower through week 20. The cumulative risk of miscarriage for weeks 5 through 20 of gestation ranged from 11 miscarriages per 100 women to 22 miscarriages per 100 women (11-22%). Based on data from comparable study populations, a range of background miscarriage rates by week of gestation for weeks 5 through 20, the cumulative risk of miscarriage, and the remaining risk of miscarriage are presented. Wider variation of miscarriage rates and risks occurred early in gestation (<14 weeks).
（1）按孕周计算的自然流产预期发生率；（2）自然流产的累积风险；以及（3）妊娠第5至20周的剩余自然流产风险。我们检索了MEDLINE数据库中截至2009年底发表的英文文章。还检索了文章的参考文献。确定有四项研究具备进行拟议计算所需的三条必要信息：（1）研究入组时的孕周；（2）妊娠结局；以及（3）发生妊娠结局时的孕周。从每项研究中提取数据并进行生命表分析方法。妊娠早期每周的自然流产率各不相同，在妊娠第13周之前的每一周，记录到的最高发生率为每1000妇女-周超过20次流产。到第14周时，所有研究的发生率变得相对可比，降至每1000处于风险中的妇女-周低于10次流产，并且在第20周时甚至更低。妊娠第5至20周的自然流产累积风险为每100名妇女中有11至22次流产（11%-22%）。基于可比研究人群的数据，给出了妊娠第5至20周按孕周划分的一系列背景自然流产率、自然流产累积风险以及剩余自然流产风险。自然流产率和风险的较大差异出现在妊娠早期（<14周）。
