The birth prevalence of each common autosomal trisomy (21, 18 and 13) increases with advancing maternal age and this is the most important epidemiological risk factor. Prevalence during pregnancy is also dependent on gestational age. Other factors claimed to influence prevalence include paternal age, ethnicity, family history, premature reproductive aging, parity, twinning, smoking, environmental exposures, maternal medical conditions, and predispositions. We review the evidence for these associations since they may provide insights into causal mechanisms. When investigating potential co‐factors it is important to adequately allow for maternal age and minimize its confounding contribution. This is well illustrated by reports of an inverse paternal age effect where there is strong correlation between parental ages. Gestational age at diagnosis, availability of prenatal screening, diagnostic testing, and elective termination of affected pregnancies and healthcare disparities also confound the studies on ethnicity, medical conditions, and predispositions or environmental factors. Data from twin zygosity studies demonstrate the importance of differences in fetal viability for affected pregnancies. We conclude that existing epidemiological evidence for most of the co‐factors discussed should currently be considered tenuous; history of Down syndrome, albeit biased, may be an exception. The co‐factors may yet provide clues to hitherto poorly understood causal pathways.

中文翻译：

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审查决定常见常染色体三体性流行的流行病学因素（母亲年龄除外）

每个常见的常染色体三体（21、18 和 13）的出生率随着母亲年龄的增长而增加，这是最重要的流行病学风险因素。怀孕期间的患病率还取决于胎龄。其他声称影响患病率的因素包括父亲年龄、种族、家族史、过早生育、胎次、双胞胎、吸烟、环境暴露、母亲的健康状况和倾向。我们回顾了这些关联的证据，因为它们可以提供对因果机制的见解。在调查潜在的共同因素时，充分考虑到母亲的年龄并尽量减少其混杂因素是很重要的。父亲年龄反向效应的报告很好地说明了这一点，其中父母年龄之间存在很强的相关性。诊断时的胎龄，产前筛查、诊断测试和选择性终止受影响妊娠的可用性以及医疗保健差异也混淆了关于种族、医疗条件、易感性或环境因素的研究。来自双胞胎接合性研究的数据证明了胎儿存活率差异对受影响妊娠的重要性。我们得出的结论是，目前讨论的大多数共同因素的现有流行病学证据应该被认为是微不足道的；唐氏综合症的病史虽然有偏见，但可能是个例外。辅助因素可能还提供了迄今为止知之甚少的因果途径的线索。和易感性或环境因素。来自双胞胎接合性研究的数据证明了胎儿存活率差异对受影响妊娠的重要性。我们得出的结论是，目前讨论的大多数共同因素的现有流行病学证据应该被认为是微不足道的；唐氏综合症的病史虽然有偏见，但可能是个例外。辅助因素可能还提供了迄今为止知之甚少的因果途径的线索。和易感性或环境因素。来自双胞胎接合性研究的数据证明了胎儿存活率差异对受影响妊娠的重要性。我们得出的结论是，目前讨论的大多数共同因素的现有流行病学证据应该被认为是微不足道的；唐氏综合症的病史虽然有偏见，但可能是个例外。辅助因素可能还提供了迄今为止知之甚少的因果途径的线索。