Babyworld , Babycentre , & BabyGenius all recommend eating live yogurt for pregnant women who suffer from thrush.
To be honest, I am struggling to find any other links that even mention mixing live yogurt and pregnancy, which pretty much suggests to me that it's never been credibly raised as a safety issue. All foods contain bacteria, it's just that "live" yogurt contiains an very high amount of the bacteria that are actively good for people.