目前，生育率降低已是全球性现象，全球有一半的人口生活在时期总和生育率低于2.1的国家里。
这个数字是什么概念呢？
一般来说，只有总和生育率高于2.1，才能达到世代更替的水平。
然而，随着人们观念的转变、经济的制约、女性生育面临的挑战、生育年龄的推迟等因素的影响，全球范围生育率在不可避免地逐年下降。
在上面诸多因素中，生育年龄的推迟是不容忽视的影响因素。
过往的医学知识和社会舆论大多宣传女性的最佳生育年龄在25~35周岁之间。
研究表明：老年果蝇生殖系统
修复能力远不如年轻果蝇
高龄会降低男性生育力：
增加不良妊娠和子代缺陷风险
全球男性精子质量
45年间出现明显下跌
如何提高精子质量？
参考文献：
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