RT Journal Article SR Electronic T1 Guidelines for the management of extremely preterm deliveries in the grey zone of viability between 23 and 24 weeks’ gestation vary widely in developed countries JF Evidence Based Medicine JO Evid Based Med FD BMJ Publishing Group Ltd SP 227 OP 227 DO 10.1136/ebmed-2015-110288 VO 20 IS 6 A1 Berger, Thomas M YR 2015 UL http://ebm.bmj.com/content/20/6/227.abstract AB