Importance  Autism spectrum disorder (ASD) is known to be more prevalent among males than females in the general population. Although overall risk of recurrence of ASD among siblings has been estimated to be between 6.1% and 24.7%, information on sex-specific recurrence patterns is lacking.

Objective  To estimate high-confidence sex-specific recurrence rates of ASD among siblings.

Design, Setting, and Participants  This observational study used an administrative database to measure the incidence of ASD among children in 1 583 271 families (37 507 with at least 1 diagnosis of ASD) enrolled in commercial health care insurance plans at a large US managed health care company from January 1, 2008, through February 29, 2016. Families in the study had 2 children who were observed for at least 12 months between 4 and 18 years of age.

Main Outcomes and Measures  The primary measure of ASD recurrence was defined as the diagnosis of ASD in a younger sibling of an older sibling with an ASD diagnosis.

Results  Among the 3 166 542 children (1 547 266 females and 1 619 174 males; mean [SD] age, 11.2 [4.7] years) in the study, the prevalence of ASD was 1.96% (95% CI, 1.94%-1.98%) among males and 0.50% (95% CI, 0.49%-0.51%) among females. When a male was associated with risk in the family, ASD was diagnosed in 4.2% (95% CI, 3.8%-4.7%) of female siblings and 12.9% (95% CI, 12.2%-13.6%) of male siblings. When a female was associated with risk in the family, ASD was diagnosed in 7.6% (95% CI, 6.5%-8.9%) of female siblings and 16.7% (95% CI, 15.2%-18.4%) of male siblings.

Conclusions and Relevance  These findings are in agreement with the higher rates of ASD observed among males than among females in the general population. Our study provides more specific guidance for the screening and counseling of families and may help inform future investigations into the environmental and genetic factors that confer risk of ASD.

重要的  自闭症谱系障碍（ASD）被称为是男性比女性在一般人群中更为普遍。尽管据估计兄弟姐妹中ASD复发的总体风险在6.1％和24.7％之间，但缺乏有关性别特异性复发方式的信息。

目的  评估兄弟姐妹中ASD的高置信度性别特异性复发率。

设计，环境和参与者  本观察性研究使用行政数据库来衡量在美国一家大型医疗机构参加商业医疗保险计划的1 583 271个家庭（37 507个，至少诊断出ASD）的儿童中ASD的发生率。护理公司从2008年1月1日至2016年2月29日。研究中的家庭有2个孩子，在4至18岁之间被观察至少12个月。

主要结果和措施  ASD复发的主要指标定义为对ASD进行诊断的年轻同龄兄弟姐妹的ASD诊断。

结果  研究中的3 166 542名儿童（女性1 547 266名和男性1 619 174名；平均[SD]年龄为11.2 [4.7]岁）中，ASD的患病率为1.96％（95％CI，1.94％-1.98）男性）和女性的0.50％（95％CI，0.49％-0.51％）。当男性与家庭中的风险相关时，女性兄弟姐妹中有4.2％（95％CI，3.8％-4.7％）和男性兄弟姐妹中12.9％（95％CI，12.2％-13.6％）被诊断为ASD。当女性与家庭中的风险相关时，女性兄弟姐妹的7.6％（95％CI，6.5％-8.9％）和男性兄弟姐妹的16.7％（95％CI，15.2％-18.4％）被诊断为ASD。

结论与相关性  这些发现与一般人群中男性比女性中更高的ASD发生率相符。我们的研究为筛查和咨询家庭提供了更具体的指导，并可能有助于将来对引起ASD风险的环境和遗传因素进行调查。