Hi Doctors, My Wife Is 29 Weeks Pregnant. Since Last

Hi doctors, my wife is 29 weeks pregnant. Since last week she has started lot of vomiting. We admitted her to a nearby hospital. Treatment was given to her for 3 days. Vomiting stopped, but again after 3days vomiting started. The doctor suggested to take Ondem and Vominos.
Please advise whether vomiting is normal in 29th week? Note : its twin pregnancy case.