Objective: We aimed to examine the long-term effects of parity, age at first childbirth, and age at last childbirth on mortality in postmenopausal women.

Methods: The data was from the Women's Health Initiative involving 106,760 postmenopausal women. We used propensity score matching to create matched samples, where each exposure group was matched with a reference group based on their propensity scores. We employed multilevel Cox proportional hazard models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) to examine the associations of parity and age at childbirth with mortality. We conducted multiple mediation analyses to estimate the effects of potential mediators on the associations.

Results: Compared to parity of 2, the HRs (95% CIs) for the association of all-cause mortality with parity of 0, 1, 3, 4, and 5+ were 1.09(1.05-1.13), 1.11(1.06-1.16), 1.01(0.99-1.04), 1.00(0.97-1.03), and 1.00(0.96-1.03), respectively. Age at first childbirth of <20, age at last childbirth of <25, and age at last childbirth ≥40 years were associated with increased mortality risks, with the corresponding HRs (95% CIs) of 1.14(1.09-1.19), 1.06(1.02-1.11), and 1.07 (1.00-1.15). Women with parity of 0, 4+, or age at first childbirth <25 years had shorter lifespans than the reference groups. Premature menopause was a significant mediator in the associations of parity and age at first childbirth with mortality.

Conclusions: We found long-term adverse impacts of nulliparity and young age at first childbirth on women's mortality risk and lifespan. Premature menopause may operate as a critical intermediate between childbirth and later-life mortality, underscoring the importance to identify at-risk women early.

Keywords: Pregnancy; Women’s Health Initiative; age at childbirth; lifespan; mediation analyses; mortality; parity; propensity score matching.

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目标： 我们的目的是探讨生育次数、初产年龄和末次分娩年龄对绝经后妇女死亡率的长期影响。

方法： 数据来自涉及106,760名绝经后女性的“女性健康倡议”项目。我们使用倾向评分匹配来创建配对样本，其中每个暴露组根据其倾向评分与参考组相匹配。我们采用多水平Cox比例风险模型估计危险比（HRs）和95%置信区间（CIs），以考察生育次数及分娩年龄与死亡率之间的关联。我们进行了多次中介分析来估算潜在中介因素对这些关联的影响。

结果： 相比生育两次，生育零次、一次、三次、四次和五次及以上与全因死亡率的HRs（95% CIs）分别为1.09(1.05-1.13)、1.11(1.06-1.16)、1.01(0.99-1.04)、1.00(0.97-1.03)和1.00(0.96-1.03)。初产年龄小于20岁，末次分娩年龄小于25岁及大于等于40岁的女性与较高的死亡风险相关，相应的HRs（95% CIs）分别为1.14(1.09-1.19)，1.06(1.02-1.11)和1.07 (1.00-1.15)。生育零次、四次及以上或初产年龄小于25岁的女性寿命较参考组短。早绝经是连接生育次数及初产年龄与死亡率关联的重要中介因素。

结论： 我们发现，无生育史和年轻初产对女性的死亡风险及预期寿命有长期不利影响。早绝经可能在分娩与晚年死亡之间起着关键的作用，这强调了早期识别高危女性的重要性。

关键词： 妊娠；女性健康倡议；分娩年龄；预期寿命；中介分析；死亡率；生育次数；倾向评分匹配。