Kate's severe morning sickness explained

While morning sickness in pregnant women is common, the problem the Duchess of Cambridge has been hospitalized with is not.

In a statement, palace officials said she was hospitalized with hyperemesis gravidarum, a potentially dangerous type of morning sickness where vomiting is so severe no food or liquid can be kept down.

Palace officials said the duchess was expected to remain hospitalized for several days and would require a period of rest afterward.

The condition most often affects women early in their pregnancy; the duchess is less than 12 weeks pregnant.

Doctors said the duchess would likely recover in a few days. Dr. Daghni Rajasingam, a spokeswoman for Britain's Royal College of Obstetricians and Gynecologists, said women with severe symptoms — including dehydration, dizziness and persistent vomiting — needed to be hospitalized for treatment, including being given fluids intravenously.

"However, this usually only means a few days in [the] hospital," she said in a statement. "The best advice for anyone suffering from [severe morning sickness] is to get plenty of rest and drink lots of fluid."

Severe morning sickness affects about one in 200 pregnant women, according to Britain's Department of Health. It is more common in young women, women who are pregnant for the first time and those expecting multiple babies.

Doctors aren't sure what causes it but suspect it could be linked to hormonal changes or nutritional problems.

If the problem is recognized and treated early, doctors say there are no long-term effects for either the mother or the child. Left untreated, the mother could be at risk of developing neurological problems — including seizures — or risk delivering the baby early.

Rajasingam said most pregnant women recover from the condition with no serious consequences.

"With early diagnosis and treatment, there is no reason why we shouldn't expect a healthy pregnancy," she said.