I had a cousin in law with Down's because his mother had been a lush all during the pregnancy..
It's hardly worth it to risk your baby's health over a drink. If you need one that bad, you have more problems than you know.
You are in the stone age dear. Down's syndrome is a chromosomal aberration that has absolutely NOTHING to do with alcohol consumption. It's more dependent on simply the age of the mother. the condition of her eggs with age or sometimes just the hand nature deals you.
As far as I know, science has never found a link to pregnant based alcoholic behavior and Downs. S##t happens.
Alcohol abuse is harmful to a fetus but Down's syndrome isn't the outcome.