1. Said M, Rais-Bahrami K . Umbilical artery catheterization and umbilical vein catheterization. In: MacDonald M, Ramasethu J, Rais- Bahrami K (eds). Atlas of Procedures in Neonatology, 5th edn. Wolters Kluwer Lippincott Williams & Wilkins: Philadelphia, PA, USA,, 2013, pp 156–179.
2. Dunn PM . Localization of the umbilical catheter by post-mortem measurement. Arch Dis Child 1966; 41: 69–75.
3. Shukla H, Ferrara A . Rapid estimation of insertional length of umbilical catheters in newborns. Am J Dis Child 1986; 140: 786–788.
4. Wright IM, Owers M, Wagner M . The umbilical arterial catheter: a formula for improved positioning in the very low birth weight infant. Pediatr Crit Care Med 2008; 9: 498–501.
5. Sritipsukho S, Sritipsukho P . Simple and accurate formula to estimate umbilical arterial catheter length of high placement. J Med Assoc Thai 2007; 90: 1793–1797.