I'd second Cai's response there, so definitely ask your doctor. Eating yoghurt is perfectly fine in pregnancy and a good way to help with thrush which is common in pregnancy.

You can take acidophilus safely in pregnancy, you need to ask your pharmacist for it as it's a live good bacteria and needs to be kept in the fridge. Inner Health sell a good dose of it and I have found it really effective in fending off thrush when you get that early feeling that it's coming. Also ideal if you've had antibiotics (after taking them, not during), been on the pill or been through lots of stress, which tends to result in an imbalance of the good gut bacteria and bad.