Mom making rude comments about husband

My husband is in remissions after 4 years of chemotherapy. Hes gained quite a bit of weight but he's only overweight by 3 pounds when he used to be underweight by 20! He is eating much more lately. I'm currently pregnant which I was worried about because chemo damages sperm but we got pregnant quickly. My mom keeps making comments saying "Why are you eating so much? My daughter is pregnant. You aren't." "You're not the pregnant one. You shouldn't be gaining weight." "There is no reason for you to still be this hungry."

It's really taking a toll on his mental health. What can I say to set boundaries with my mother.