Morning sickness

Morning sickness is nausea, sometimes accompanied by vomiting, during pregnancy. It commonly begins early in pregnancy and can occur at any time of day.

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Human chorionic gonadotropin: A hormone produced mainly by the placenta that supports early pregnancy and is measured by pregnancy tests. Its rapid rise in early pregnancy is associated with nausea, though it does not explain every case.
Pyridoxine: Vitamin B6, a water-soluble vitamin involved in metabolism and nervous-system function. It is commonly used as an initial medicine for pregnancy-related nausea.
Hyperemesis gravidarum: A severe form of pregnancy-related nausea and vomiting that can cause dehydration, weight loss, or metabolic disturbance. Unlike typical morning sickness, it can seriously impair hydration and nutrition and may require medical treatment.
Dehydration: A deficit of body water that can impair normal physiological function. Repeated vomiting can reduce fluid levels, especially when drinking is difficult.
Placental growth factor: A protein involved in placental blood-vessel development and function. Research examines placental signals as possible contributors to differences in pregnancy nausea.
Estrogen: A group of hormones involved in reproductive development and function. Changing estrogen levels may contribute to nausea and heightened sensitivity to smells during pregnancy.
Doxylamine: An antihistamine that can cause drowsiness and is used in some combination medicines. Combined with pyridoxine, it is an established treatment for nausea and vomiting in pregnancy.
Gastroenteritis: Inflammation of the stomach and intestines, commonly causing vomiting and diarrhea. Infection can cause similar symptoms, but often includes features such as diarrhea or fever.
Electrolyte imbalance: An abnormal concentration of charged minerals in body fluids. Prolonged vomiting can disturb potassium, chloride, and other electrolyte levels.
GDF15: A stress-response hormone that can act on brain pathways involved in appetite and nausea. Its role in pregnancy vomiting is an active area of research into biological susceptibility.