Pregnancy does create an increased risk for gingivites and other issues. It's recommended you get your teeth cleaned even more regularly while pregnant. To technicaly it's normal to have tooth problems while pregnant, but you should still get it taken care of right away.
No - I'd define go to dentist to get it checked. I had to have several fillings during my pregnancies. You don't want a decaying tooth to decay so badly that it becomes infected - at any time, really, but especially during pregnancy.