Your teeth/gums do become more sensitive during pregnancy. no sugesstions, but it is common.
There is no real way to stop it. I've always taken really good care of my teeth and still do. once I was around 15 weeks they became very sensitive to heat+cold and pressure. I'm 35 weeks now and nothing has changed and my teeth still are having problems. my dentist tried having me change to a softer tooth brush and toothpaste for sensitive teeth and it has not helped at all. :(