I can't imagine wanting to go to a hens night that close or going to a wedding 4 days ODor 4 days post birth (eg I have had c/sect so 4 days post birth would not have been possible anyway) but in saying that would the option of going (with bubs in tow given so young) if bubs came early (eg a couple of weeks) be worth considering??? Maybe if you broach it from that respect it might show that you really want to go but the practicalities at that stage of pregnancy just don't allow. If late numbers aren't flexible then you probably need to say no I can't come but know I'm thinking the best for you.