An obviously ill animal, pregnant or not, would be a target for predators, so a nauseous pregnant animal wouldn’t last very long, and also compromise the species if this happened too frequently.
However, I have heard that it’s not uncommon for cats, who are notorious pukers anyway, to do so more frequently in early pregnancy, and newly freshened goats often have a reduced appetite right at first.
I don’t think it’s as serious a problem for predators in general, and I’m not positive vomiting is the best attractor for predators. I recall some big cats have been noticed avoiding sick prey, although I’m sure a lot of predators would zero in on pregnant prey. I don’t know this for a fact, but urine might give away a pregnant female more than vomiting would.
But puking may appear in pregnant humans but the same conditions exhibit differently in other animals.