I'm going to bartending school in about a year, this situation made me think.

In conclusion to that, I've made my decision.

No, I wouldn't serve the stupid bitch.
There are other bars and other bartenders. I'm not going to waste my time with a drunk pregnant women and I'm not going to be at risk to be sued when the baby comes out with Fetal Alcohol Syndrome. While it won't be my fault the dumbass drank, it's not mcdonald's fault the fatass ate. No reason to risk it.

While a part of my motherly instincts cares for the baby-to-be, the rest of me doesn't. I just want to keep my ass innocent.

UNLESS I would get fired.
That might be a different story.

Edit:
I would have to be 100 percent sure she's pregnant. Only after the words "im pregnant" or "the baby's due on..." come out of her mouth would I rethink serving her.