Morning sickness is extremely common during pregnancy -- up to 80% of people report experiencing it. It's not as severe as hyperemesis gravidarum and doesn't cause dehydration or weight loss.You might need treatment in a hospital with IV fluids (fluids given intravenously, or through your vein) if you become dehydrated.Morning sickness may cause occasional vomiting and nausea, but you should still be able to keep food and liquids down most of the day.It tends to subside or disappear completely after 12 weeks of pregnancy (the first trimester).Hyperemesis gravidarum causes you to vomit several times per day.This can eventually lead to weight loss and dehydration.Symptoms of HG often last longer than morning sickness.