Background: The impact children with complex healthcare needs have on the healthcare system is significant and requires a multidisciplinary response. Congenital anomaly (CA) is a group of conditions requiring complex and variable input from primary and secondary healthcare. This thesis explores the literature on health system preparedness for children with complex healthcare needs and quantitatively describes healthcare use for a population of children with CA, an exemplar for children with complex healthcare needs. Methods: Routine health data from primary care was explored to identify children with CA and linked to secondary care data, outpatient records, and questionnaire data from a multi-ethnic prospective birth cohort over a five-year period. Rates of CA were calculated and healthcare use for children with and without CA was analysed. Results: Out of a birth cohort of 13,857 children, 860 had a CA. Using primary care data for children aged 0 to 5 years, the number of children with CA was found to be 620.6 per 10,000 live births, above the national rate of 226.5 per 10,000 live births. Healthcare use was higher for children with CA than those without CA. Demand for use of hospital services for children with CA was higher (Incident rate ratio (IRR) 4.38, 95% confidence interval (CI) 3.90 to 4.92) than demand for primary care services (IRR, 1.27, 95% CI 1.20 to 1.35). Conclusion: These results suggest that using primary care data as a source of CA case ascertainment reveals more children with CA than previously thought. These results have significant implications for commissioning healthcare services for children with complex healthcare needs.