将下列内容翻译成完整的英语句子，保持原意不变，完整表达。先说一个重要的任务是观察儿童，接着说这时候很难识别自闭症状况，进一步说原因是因为自闭症之前多年没有明显的迹象，最后强调即使有经验的儿科医生也无法时刻察觉。
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A crucial task is to observe children, at which time it is challenging to recognize autistic conditions, further explained by the fact that years may pass with no apparent signs of autism before its onset, and even experienced pediatricians cannot always detect it.
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