Expectant mothers’ illness

Anybody heard of a family member (in the same house) falling sick due to the presence of a pregnant mum? Currently staying with my MIL and she hasn’t been well for the past week. Kept saying it’s because of me as I don’t have any morning sickness, only fatigue; so it kind of “passed it on” to her instead. I find this rather hurtful as I don’t believe in such nonsense.