My MIL told me to forget about taking a shower or washing my hair one month after giving birth or I will be plagued by headaches and rheumatism for the rest of my life. Any truth to this?

I take at least 3-5 showers a day in this weather, I can't imagine not being able to shower or wash my hair during confinement. Everytime someone tells me that. My response was, "not Gg to happen to me", ESP when I am planning to breast feed, I have to be clean at all times. However, I will take extra care to keep dry and avoid catching a cold.