Pregnancy and medication is a complicated issue at the best of times. There was quite some time that pregnant mothers were discouraged from getting the vaccine due to the unknown affect on the fetus. It was just last month when the CDC said it was safe for pregnant women to get vaccinated.
Now I'm in no way shape or form excusing nutjob anti-vaxxers, but in the case of pregnant women it was pretty acceptable for them to forgo vaccination, at least earlier this year.
Now there is no excuse unless you are also immunocompromised or have other complicating factors.