Comparison of NSCH Study sample with US population data on adverse perinatal outcome for same birth cohorts^*

Perinatal outcome	US natality data from published reports						Current NSCH study sample (birth cohorts include 1994 to 2008)
	1994	1998	2001	2004	2006	2008	Total study sample (weighted), n = 74,565	Sample limited to children without DDs (weighted), n = 64,478
% PTB	11.0	11.6	11.9	12.5	12.8	12.3	11.5	10.5
% LBW	7.3	7.6	7.7	8.1	8.3	8.2	9.3	7.5
% VLBW	1.0	1.5	1.4	1.5	1.5	1.5	1.5	1.2

^*There are some known differences in populations represented by NSCH and birth cohorts. NSCH data do not represent US children who died or migrated out of the country shortly after birth. Conversely, US birth cohort natality data do not include children who were born outside the United States and subsequently migrated into the United States.