This study was designed to track the developmental trajectory, during the first 24 months of life, of 335 low-risk infants later diagnosed with Autism Spectrum Disorder and identify early deviations observed in routine Well Care checkups. We compared their achievements to typically developing children and to children later diagnosed with non-autistic developmental impairments. The results show that in the first 6 months, the children with autism showed normal acquisition of milestones, whereas by 9 months of age they began to fail the language/communication, as well as motor items when compared to typical and delayed non-autistic children. Regular check-up visits may be useful in detecting early failure in achieving milestones, leading to earlier referral for further evaluation and treatment.