Nausea and Vomiting of Pregnancy: Causes and Potential Benefits

Nausea and vomiting of pregnancy (NVP) affects up to 85% of pregnant women, and while commonly referred to as “morning sickness,” most affected women experience symptoms throughout the day.1 While the condition is usually mild and transient, peaking at around 9 weeks gestation and resolving by 16 weeks gestation, some cases can last longer and/or be quite severe. The most serious cases, called hyperemesis gravidarum, can lead to fluid, electrolyte, and acid-base imbalances, as well as nutritional deficiencies, weight loss, and the need for hospitalization.

Researchers have been investigating why nausea and vomiting arise so often and usually at such a predictable time during pregnancy. “The cause is not known, but it may result from a hormone secreted by the placenta. In women who suffer throughout the entire pregnancy, there’s total relief the minute the placenta is ejected from mom’s body,” says Gideon Koren, MD, director of the Motherisk Program at the University of Toronto’s Hospital for Sick Children.