Department of Obstetrics and Gynecology, McGill University Health Centre, Montreal, Canada.
Department of Epidemiology, Biostatistics, and Occupational Health, McGill University, Montreal, Canada.
Hum Reprod. 2022 Jul 30;37(8):1896-1906. doi: 10.1093/humrep/deac086.
Is parents' age at birth associated with daughters' fecundability?
Daughters born to mothers <25 years or fathers ≥35 years had slightly lower fecundability.
Two recent studies reported lower fecundability in women born to mothers <20 years, which may be partly due to daughters of young mothers being less likely to plan their pregnancies.
STUDY DESIGN, SIZE, DURATION: A retrospective cohort study of 58 496 pregnancy planners (4290 of whom conceived with treatment) and 14 194 non-planners enrolled in the Norwegian Mother, Father and Child Cohort Study (MoBa) between 2000 and 2008, linked with the Medical Birth Registry of Norway.
PARTICIPANTS/MATERIALS, SETTING, METHODS: Participants were born in Norway between 1967 and 1990. We estimated fecundability ratios (FRs) and 95% CI as a function of both parents' (F1) age at the daughter's (F2) birth among non-treated planners and the relative risk of time to pregnancy (TTP) ≥12 months or treatment among all planners. We explored whether daughters of young mothers were under-represented among planners, compared with the underlying population. Finally, we estimated FRs after adding non-planners, randomly assigned to conceiving in the first cycle with probabilities of 0.60 and 0.70.
For both mother and father, the reference category was 25-29 years. Fecundability was slightly lower among daughters of older fathers (FRs (95% CI): 0.95 (0.92, 0.98) for F1 father's age 35-39 years and 0.93 (0.89, 0.97) for ≥40 years) and daughters of young mothers (0.92 (0.89, 0.96) for F1 mother's age <20 years and 0.97 (0.95, 0.99) for 20-24 years). Results were similar for the composite outcome TTP ≥ 12 months or treatment, although driven by TTP ≥ 12. Compared with Norwegian-born women with ≥1 pregnancy, planners born to mothers <20 years were underrepresented. Including non-planners with very high fecundability weakened the association with mother's age <20 years.
LIMITATIONS, REASONS FOR CAUTION: This was a pregnancy cohort with retrospectively reported information on planning and TTP. Selection bias appears unlikely to fully explain the association with mother's age <20 years.
Daughters of young mothers or older fathers may have slightly lower fecundability. If corroborated, the finding about older paternal age is relevant, given the widespread tendency to delay childbearing.
STUDY FUNDING/COMPETING INTEREST(S): This work was partly funded by the Research Council of Norway (project no. 320656), and through its Centres of Excellence funding scheme (project no. 262700). M.C.M. has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement no. 947684). No competing interests.
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父母的生育年龄是否与女儿的生育能力有关？
母亲年龄<25 岁或父亲年龄≥35 岁的女儿生育能力略低。
最近的两项研究报告称，母亲年龄<20 岁的女性生育能力较低，这可能部分是因为年轻母亲的女儿不太可能计划怀孕。
研究设计、大小、持续时间：这是一项回顾性队列研究，涉及 58496 名妊娠计划者（其中 4290 名通过治疗怀孕）和 14194 名非计划者，他们于 2000 年至 2008 年期间在挪威母亲、父亲和儿童队列研究（MoBa）中注册，并与挪威医学出生登记处相关联。
参与者/材料、设置、方法：参与者于 1967 年至 1990 年期间在挪威出生。我们估计了非治疗计划者中父母（F1）年龄与女儿（F2）出生之间的生育能力比（FR）和 95%置信区间（CI），以及所有计划者中怀孕时间（TTP）≥12 个月或治疗的相对风险。我们探讨了年轻母亲的女儿是否在计划者中代表性不足，与基础人群相比。最后，我们在添加了非计划者后估计了 FRs，非计划者随机分配到第一个周期的受孕概率为 0.60 和 0.70。
对于母亲和父亲，参考类别均为 25-29 岁。父亲年龄较大（FRs（95%CI）：35-39 岁为 0.95（0.92，0.98），≥40 岁为 0.93（0.89，0.97））和母亲年龄较小（FRs（95%CI）：F1 母亲年龄<20 岁为 0.92（0.89，0.96），20-24 岁为 0.97（0.95，0.99））的女儿生育能力略低。复合结局 TTP≥12 个月或治疗的结果相似，尽管这是由 TTP≥12 驱动的。与有≥1 次妊娠的挪威出生女性相比，母亲年龄<20 岁的计划者代表性不足。包括生育能力非常高的非计划者，削弱了与母亲年龄<20 岁的关联。
局限性、谨慎的原因：这是一项妊娠队列研究，回顾性报告了计划和 TTP 信息。选择偏差似乎不太可能完全解释与母亲年龄<20 岁的关联。
年轻母亲或年长父亲的女儿生育能力可能略低。如果得到证实，关于父亲年龄较大的发现是相关的，因为普遍存在延迟生育的趋势。
研究资金/利益冲突：这项工作部分得到了挪威研究理事会（项目编号 320656）的资助，并通过其卓越中心资助计划（项目编号 262700）。M.C.M. 收到了欧洲研究理事会（ERC）的资助，该理事会是欧盟地平线 2020 研究和创新计划的一部分（授予协议编号 947684）。没有竞争利益。
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