1. Royal College of Obstetricians and Gynaecologists (RCOG). Tocolysis for women in preterm labor. Green-top Guideline No. 1B; 2002.
2. Lawn JE, Cousens SN, Darmstadt GL, et al. 1 year after the Lancet neonatal survival series—was the call for action heard? Lancet. 2006;367:1541–7.
3. Arisoy R, Yayla M. Transvaginal sonographic evaluation of the cervix in asymptomatic singleton pregnancy and management options in short cervix. J Pregnancy 2012;2012:201628:doi: 10.1155/2012/201628.epub.2012 .
4. Norwitz ER, Caughey AB. Progesterone supplementation and prevention of preterm birth. Rev Obstet Gynecol. 2011;4(2):60–72.
5. Romero R, Yeo L, Miranda J, et al. A blueprint for the prevention of preterm birth: vaginal progesterone in women with a short cervix. J Perinat Med. 2013;41:27–44.