Royal Pregnancy: One Wash U Professor Weighs In

News that England's Prince William and his wife, Catherine, Duchess of Cambridge, are expecting their first child spread like wildfire today.

According to the Guardian (UK) newspaper, the news that the duchess is in the "very early stages" of pregnancy with the third-in-line to the throne was officially released after she was taken to the King Edward VII hospital in central London, suffering from hyperemesis gravidarun, very acute morning sickness.

Washington University's George Macones told USA Today that less than 1% of all pregnant women are hospitalized for vomiting.

Quoting from the USA Today story:

In most cases, nausea and vomiting go away by the second trimester, or about 13 or 14 weeks into the pregnancy, Macones says. A few unlucky women may have severe vomiting throughout pregnancy, and require intravenous nutrition.

There's no reason to believe that excessive vomiting is caused by a problem with the baby, Macones says. However, the condition can be more common in women carrying twins or triplets. Doctors believe the cause of nausea and vomiting during pregnancy to be rapidly rising blood levels of a hormone called HCG, or human chorionic gonadotropin, which is released by the placenta, according to the National Institutes of Health.