Table 1. Coverage of HES birth cohort compared to national statistics published by the ONS for England.

Year of birth	HES birth cohort	England (according to ONS)*	coverage
1998	546,804	584,928	93.5%
1999	542,734	572,611	94.8%
2000	526,254	556,172	94.6%
2001	527,602	547,292	96.4%
2002	540,030	549,003	98.4%
2003	554,104	572,711	96.8%
2004	571,530	589,248	97.0%
2005	577,964	595,019	97.1%
2006	592,768	616,588	96.1%
2007	602,801	635,561	94.8%
2008	631,027	652,280	96.7%
2009	630,170	649,416	97.0%
2010	649,431	665,746	97.5%
2011	650,223	666,320	97.6%
2012	653,116	672,505	97.1%
2013	626,619	646,941	96.9%
2014	614,637	640,663	95.9%
2015	616,184	643,363	95.8%
total	10,653,998	11,056,368	96.4%

HES = Hospital Episode Statistics. ONS = Office for National Statistics.

*We estimated the number of singleton live births in England based on the number of total births in England [34, 35] and assuming that the ratio of singleton live births to all live births was the same in England as in England and Wales (97.0% in 1998–2015) [37–39].