Results: A total of 17 newborns and 11 mothers were confirmed to have inborn errors of metabolism, including 5 primary carnitine deficiency, 1 citrullinemia, 1 MMA; 2 MSUD, 2 GA I, 1 GA II, 2 IVA, 1 PA, 1 VLCAD deficiency, 1 CPT I deficiency, 8 maternal primary carnitine deficiency, 2 maternal beta-ketothiolase deficiency and 1 maternal GA I. The overall incidence of IEM in Bangkok identified by expanded newborn screening was approximately 1:9,697 live births or 1: 5,888 including mothers. The gene discussed is CPT1A; the disease is systemic primary carnitine deficiency disease.