. Author manuscript; available in PMC: 2017 Feb 1.

Published in final edited form as: Am J Perinatol. 2016 Jan 22;33(3):318–328. doi: 10.1055/s-0035-1571202

Table 1. Characteristics of Select Cohort Studies Reporting Gestational Age Specific Survival for Extremely Preterm Infants.

Study	NICHD NRN	EPIPAGE-2	NRN	PBFT	EPICure	EXPRESS	KKH
Country	United States	France	Japan	Taiwan	United Kingdom	Sweden	Singapore
Year(s)	2008-2011	2011	2003-2005	2007-2012	2006	2004-2007	2000-2009
Sample size	7124	1911	1057	1718	2034	707	887
Gestational ages	22⁰/₇-28⁶/₇ wk	22⁰/₇-28⁶/₇ wk	22-25 wk	<29 wk	<27 wk	<27 wk	<29 wk
Numerator	Survival to discharge	Survival to discharge	Survival to discharge	Survival to discharge	Survival to discharge	Survival to 1 year	Survival to discharge
Denominator	Live births (inborn)	Live births	Live births	Live births admitted to centers	Live births	Live births	Live births admitted to center
Study cohort	25 academic medical centers	Population-based cohort	48 tertiary centers	5 centers part of PBFT	Population-based cohort	Population-based cohort	Single large tertiary referral center
Reference	⁵	⁷	¹⁰	¹¹	¹²	¹³	¹⁴

Abbreviations: NICHD, National Institute of Child Health and Human Development; NRN, Neonatal Research Network; EPIPAGE-2, Etude Epidémiologique sur les Petits Ages Gestationnels 2; PBFT, Premature Baby Foundation of Taiwan; EXPRESS, Extremely Preterm Infants in Sweden Study; KKH, KK Women's and Children's Hospital.