Characteristics and results of the present study compared with the former five meta-analyses.

Azoo-azoospermia; OAT-oligoasthenoteratozoospermia; Oligo-oligozoospermiaHB, hospital-based controls; PB, population-based controls+, positive result−, negative resultNA, not availableCharacteristics and results of the present study compared with the former five meta-analyses.无精子症（Azoo-azoospermia）、少弱畸精子症（OAT-oligoasthenoteratozoospermia）、少精子症（Oligo-oligozoospermia）；医院来源对照（HB, hospital-based controls）、人群来源对照（PB, population-based controls）；+ 代表阳性结果，− 代表阴性结果，NA 代表不可用（not available）。本研究的特征与结果与此前五项荟萃分析的对比。