To gain a holistic approach for parental help-seeking behavior and ASD diagnosis, this study aimed to use two national birth cohort study datasets to investigate the pathway relationship between personal and social/environmental factors, including maternal perceived childcare pressure, maternal level of education, urbanization at age 3, and the chance of receiving a autism spectrum disorder (ASD) diagnosis at when children are aged 5.5years (2.5years later). The 2003 Taiwan Birth Cohort Pilot Study (TBCS-p; N = 1618) and 2005 Taiwan Birth Cohort Study (TBCS; N = 19,183) datasets were used. The TBCS-p and TBCS both showed similar prevalence of ASD (0.3-0.4%). Children with ASD characteristics, as measured using the Modified Checklist of Autism in Toddlers, had 8.27-18.20times increased likelihood of receiving ASD diagnosis [TBCS confidence interval (CF) of 5.32-12.86; TBCS-p CF of 2.03-163.46]. Pathway analysis showed that, although having a mother with higher education or who lived in a city decreased the chance for ASD diagnosis, the interactive effect of a maternal higher level of education and living in a city led to an increased likelihood for ASD diagnosis. Additionally, mothers who perceived a higher level of childcare pressure were also more likely to seek medical assistance and diagnosis. Access to healthcare (living in the city), maternal level of awareness (level of education), and perceived childcare pressure are all factors that influence help-seeking behavior and diagnosis. Therefore, medical professionals should pay special attention to the developmental condition of children in underserved backgrounds and rural areas to prevent delayed diagnosis.