Treating morning sickness PRN?

Question I received a telephone call from my sister who lives in the United States. She is experiencing moderate symptoms of morning sickness, but she tells me that she was advised to treat her symptoms only pro re nata- meaning, when symptoms re-emerge. Does this make sense? Answer No, it does not. Typically, nausea and vomiting of pregnancy continue for weeks and months, and in some cases until labour. It is critical to treat symptoms consistently so the woman can maintain adequate fluid and calorie intake. When symptoms improve, the dose of antiemetic medication should be decreased gradually.