1. World Health Organization: Preterm birth: fact sheet. 2014, [ http://www.who.int/mediacentre/factsheets/fs363/en/ ]. Accessed April 27
2. Goldenberg RL, Culhane JF, Iams JD, Romero R: Epidemiology and causes of preterm birth. Lancet. 2008, 371: 75-84. 10.1016/S0140-6736(08)60074-4.
3. Lumley J: Defining the problem: The epidemiology of preterm birth. B J Obstet Gynaecol. 2003, 110 (Suppl 20): 3-7.
4. Institute of Medicine (US) Committee on Understanding Premature Birth and Assuring Healthy Outcomes: Preterm Birth: Causes, Consequences, and Prevention. Edited by: Behrman RE, Butler AS. 2007, Washington, D.C: The National Academies Press
5. Baig SA, Khan N, Bagai T, Fatima A, Karim SA, Aziz S: Preterm birth and its associated risk factors. A study at tertiary care hospitals of Karachi, Pakistan. J Pak Med Assoc. 2013, 63: 414-418.