My 4-week old daughter struggles to go longer than 3 hours between feeds at night and its very tiring. I've been told that introducing a late night forumla feed (say 11pm) at 6 weeks will help her sleep through the night, or at least only wake once. As the advice is all about 'exclusive' breast feeding, does anyone know how this feed will affect the benefits she gets from breast milk? I would express at this time to keep my supply up, but like the idea of getting more sleep!