Did you start yours as soon as you started TTC or did you wait til you got your BFP, if you were closely monitoring the situation with TTC? I took the vits for the first month of TTC and when nothing happened I realised that I could be months and months at this TTC game and the vits are expensive (and make me feel nauseaus and stop me sleeping!). As far as I am aware they can only really help with development once the baby is attached to you which happens around week 6 I think... I could be opening myself up for a slating here I guess but I read reports on alcohol consumption prior to week 6 of pregnancy wasnt a problem as prior to that there is no direct absorbsion from the mother by the baby.
I have a good balanced diet and do not consider taking vitamins normally.