MIL always on me about my weight

Y’all this is my fifth baby. I’ve had them back to back.6,4,3,1 and every time I’m pregnant my MIL has to say something about how big I am. With my last pregnancy which was in the summer she told me I looked like a whale. My husband never hears her comments because she’s stealthy like that. I love food don’t get me wrong but I’m pre baby a size 6 at the smallest she’s a 0. It disgusts her that my hubby loves my body while pregnant. I plan on talking with her but wanted some advice on the most straightforward way without being rude to her.