Personally I don't think it's ever ok to drink alcohol while pregnant.

BUT

I didn't know I was pregnant with my 3rd so for almost 7 mths, I had cravings for alcohol so I drank a bottle of wine a night and binged (like got blotto) on weekends. I wouldn't have done it had I known. I had to see a specialist at the Royal Womens Hosp who couldn't confirm whether I had done any damage to the baby or not until she was born. I stopped as soon as I found out I was pregnant. Luckily she is a healthy 6 year old now, there was no damage done. I would NEVER be able to forgive myself had there been something wrong. I still to this day feel guilty over it.