Abstract：
Although the global population continues to increase, the total fertility rate in many high-income countries (HICs) is below replacement, a trend apparent over several decades. The timing and pace of this change will shape the age distribution in these countries, leading to an increasing proportion of older people. The well-established links of the \"demographic transition\" between improving female education and improved access to contraception continue to drive down the fertility rates in low-/middle-income countries. However, changes in the age distribution will not be as marked as in HICs in the coming decades. These relationships may now be changing in some HICs with greater prosperity at both the personal (in some sectors of society) and national levels, linked to an increase in the total fertility rates despite continuing trends toward older age at first birth. Key drivers in these countries include improved provision of free/low-cost childcare, paid parental leave, and higher paternal contributions to childcare. However, there is also an increase in the number of women who do not have children or who may be unable to complete their family plans. Coronavirus disease 2019 and environmental factors, including the increasing prevalence of obesity, add to pressures on the fertility rates. Variable knowledge of the realities of female reproductive aging, particularly by men, is also a contributing factor, and this complex mix has fueled the increase in the number of elective egg freezing.
摘要：
在全球人口持续增加的同时,许多高收入国家的总生育率低于更替率，几十年来明显的趋势。这种变化的时间和速度将决定这些国家的年龄分布，导致老年人比例越来越高，改善女性教育和改善避孕手段之间的“人口转变”的既定联系继续降低低收入/中等收入国家的生育率。然而，在未来几十年中，年龄分布的变化将不会像高收入国家那样明显。在一些高收入国家，这些关系现在可能正在发生变化，这些国家在个人层面(在社会的某些部门)和国家层面都更加繁荣，尽管第一胎的年龄持续增加，但与总生育率的增加有关。这些国家的主要驱动因素包括改善免费/低成本儿童保育的提供，带薪育儿假,和更高的父亲对儿童保育的贡献。然而，没有孩子或可能无法完成家庭计划的妇女人数也有所增加。COVID-19和环境因素，包括肥胖率的上升，增加了生育率的压力。对女性生殖衰老现实的可变知识，尤其是男人,也是一个促成因素，这种复杂的混合物也推动了选择性卵子冷冻的增加。
