When we were ttc 1st time round, I couldnt bring myself to buy anything at all. With having fertility problems myself, and my mum having a history of many recurrent miscarriages - I just dare not buy anything.
DH bought 'The Baby' two bunny rabbits when I was about 8 weeks and I was so upset, incase it tempted fate
I think I was around 25+ weeks before we bought anything else.
We werent ttc 2nd time round (but also not doing anything active to not either ifkwim!) so didn't have the chance to think about buying anything before hand.
Although about 6 months before I found out I was expecting Eleanor, tots bots did have an amazing offer on their white cotton nippa nappies - which made them about £2 each, so bought a white bundle 'incase'
So I guess what Im saying is... Im on the fence & it really depends whether its baby #1 or #2/3+ or any history of problems.