My MIL had severe m/s and had to be hospitalised a couple of times during her 4 PG's. She also had a light period every month. Not sure if it's related to the m/s or not.
One thing I remember her saying is that she is sure that the stomach acids destroyed her teeth so she was onto me when I was PG and vomiting to constantly swish water in my mouth JIC. Thankfully I had nowhere near as a bad a time as that.