将所有的研究的数据合成，对于分类变量效应指标为风险比，对于连续型变量效应指标为加权均数差，根据研究样本的大小来加权。

Data were pooled across studies, and relative risks for categorical outcomes and weighted mean differences for continuous outcomes, weighted according to study sample size, were calculated.

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新生儿评价组的标准方法，使用相对危险度(RR)，风险差(RD)和加权均数差(WMD)。

Standard methods of the Neonatal Review Group with use of relative risk (RR), risk difference (rd) and weighted mean difference (WMD).

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