Written informed consent will be obtained from the parents or guardians of the participants at the time of enrolment. Prospective and retrospective data will be collected. Complete family and medical history, physical examination and laboratory findings will be recorded on standard case report form. Disease activity will be scored using the Paediatric Crohn's Disease Activity Index for children with CD and the Pediatric Ulcerative Colitis Activity index for those with UC. Endoscopic data will be reviewed and disease location will be classified according to Paris classification. Puberty will be assessed based on the development of secondary sexual characteristics. At the time of enrollment and after 1 year, anthropometric measurements including height, weight, triceps skin fold thickness, middle arm circumference and assessment of body composition by bioelectrical impedance will be performed for each child. Anthropometric data will be standardized by generation of z-scores for height and weight based on age and gender. Growth deficiency for height and weight measurements will be defined as a z-score\-2.