Em, when I fell pg with my DS, DD was only 7mths. She was onto solids but still having 4-6 feeds during the day and 1-2 overnight. I fed her right through til she was 15mths, so about 6wks before DS was due.

I never noticed a drop in supply - or I must have had a really patient baby who just kept feeding without getting upset if my supply had dropped.

And don't forget one of the best ways to increase your supply is to just let baby feed as much as they want