Dear Rod, I am not a doctor or a professional, but I am a woman who is pregnant. I would say that what your wife is going through is normal.
Every pregnancy is different as is every woman with child is different.
I know that I did not feel like having sex at all during my first trimester. In my second trimester, the tables turned and I wanted to sex a lot more than usual. A lot of the time, these changes are hormonal. The one thing that turns me on, no matter what the case-is to be romanced. We really, really need it.