haven't had time to read all the responses, but left my dd first overnight at 4 months.... its up to you, but can i just say, the younger they are the EASIER it is for them to be left with another care giver.... as babies all they need is someone to care for them, keep them warm, fed and safe.... its when they become toddlers that they are alot more aware of where mum and dad are (or aren't) and it is a hell of a lot harder for everyone involved to leave them..... especially if they go through a period of anxiety at being left.......

make sure you get some time to yourself while your little one's needs are basic.... honestly its harder as they get older!!!!!!!!!!!!!!