This retrospective study aims to describe head circumference (HC) developmental course during the first year of life in 50 Italian children with autism spectrum disorder (ASD) and in a control group of 100 typically developing children (TD). To this end, we use anthropometric measurements (HC, body height, body weight) obtained at birth (T0), 1-2 months (T1), 3-5 months (T2) and 6-12 months (T3) from paediatricians and reported in the infant's "baby book". Data indicate that at T2 and T3 HC was significantly greater in ASD group compared to TD, while from T1 weight was significantly smaller in ASD subjects compared to healthy infants. After controlling for weight and height, ASD HC shows an excessive rate of growth from birth. The abnormal HC growth is present in the majority of infants with ASD and could represent a biomarker that together with other clinical signs might promote an early ASD identification. (Contains 3 tables and 1 figure.)