when I was pregnant, my husand and I were aprehensive about me masturbating, because I normally masturbate laying face down in bed, and hump my pillow. I was particularlly concerned how putting my weight on my stomach and bucking back and forth might might harm my baby. It was a nurse practitioner who specialized in women's health who assured me all the humping I did wouldn't rupture the protective wall of the uterus. So, to make a long story short, I masturbated all through my pregnancy, and even humped my pillow the night before my caesarian. And so, if all my pumping up and down on my stomach didn't hurt my baby, I think your baby will be safe, no matter how much your wife masturbates.

Did her doctor say no sex?

I would think not. In fact, sexual energy can enhance and energize the whole body, as blood flow increases during orgasm. Plus, she'll be more relaxed.