I haven't had to give work a letter, instead I need to fill in a form toward the end of the pregnancy. HR have booked a meeting for mid April to see how I am travelling and to confirm when I wish to take leave and then I meet them for an exit interview in case I don't come back. All in all they were very easy going about it all and have a system in place for it. The only thing they said was I would need a medical certificate to work past 34 weeks but I am planning on finishing up at the end of 33 weeks so no worries there.