Overall, it was pretty tasteless and just about as crude as I expected it to be. I thought the abortion remark she made was simply disgusting...
"Don’t knock it ‘til you try it — and when you do try it, really knock it. You know, you’ve got to get that baby out of there."
I think whether you're pro-life or pro-choice, we can all agree that abortion is not something to celebrate as good, in and of itself. Not saying she shouldn't have been allowed to say it, just saying that it's sad that this is what passes for humor.
I don't know, maybe you were so disgusted you missed the second half of this joke, otherwise you clearly missed the complications in her routine. She was not just telling a collection of ad-libbed jokes as some slow on the uptake people here have suggested. To me, this was the best part of her routine, not for this line you've quoted here, which is tasteless, but because it was a set up. I was like you, initially thinking to myself "oh dear, has she finally gone over the edge?"
But, she soon made it clear that joke was meant to be unfunny and in poor taste when she quickly followed up by saying (this isn't her exact line but it's very close) "A lot of groans. Much of the audience here is clearly anti abortion...except when they ask their mistresses to have one." (And the aside: "different standards for different times.")
She laid the trap for them, and they fell in it. That's about as brilliant as a comedian can get.