Source: Arch Internal Med,
Date published: 14/02/2012

Source: Cochrane Library,
Date published: 05/02/2012

Source: Medusa,
Date published: 23/12/2011

Source: JAMA,
Date published: 13/10/2011

Source: American Journal of Obstetrics and Gynecology,
Date published: 10/08/2011

Source: Lancet,
Date published: 04/08/2011

Source: Cochrane Library,
Date published: 20/05/2011

Source: Circulation,
Date published: 12/04/2011

Source: UK Teratology Information Service,
Date published: 29/03/2011

Source: PLoS One,
Date published: 07/02/2011