Hyperemesis gravidarum is a severe form of morning sickness that is most common during the first 3 months of pregnancy. It is related to the high level of hormones that are present in the mother's bloodstream during pregnancy.

In most cases, hyperemesis gravidarum causes only mild nausea with occasional vomiting. However, severe cases can result in dehydration and malnutrition. If left untreated, this can trigger a miscarriage.