Prevalence of childhood autism (n = 18). Dots indicate prevalence estimates in reviewed studies. Horizontal lines indicate 95% CIs. Vertical line indicates pooled prevalence estimate in the meta-analysis. The heterogeneity of 18 studies was high (I2 = 83.7%). Prevalence estimates were presented for each reviewed study on childhood autism with 95% CIs. Reviewed studies were divided into three groups according to publication period: 2000 to 2004, 2005 to 2009 and 2010 to 2011. The pooled prevalence estimates for all reviewed studies and studies in each period were generated by a random effect meta-analysis model. There is an increase in the pooled prevalence estimates of childhood autism over time. CIs, confidence intervals.