The Slatest

Kate Middleton Has Been Hospitalized With “Hyperemesis Gravidarum.’ What Is That?

Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge receive a gift during an official visit to the Guildhall on Nov. 28, 2012, in Cambridge, England

Photo by Arthur Edwards/WPA Pool /Getty Images.

The Royal Palace announced Monday that Prince William and Kate Middleton are expecting their first child. The royals aren’t saying exactly how far along the Duchess of Cambridge is, but the pregnancy has reportedly not yet passed the 12-week mark, the point at which most people wait to go public with the news.

While tabloids have been speculating for weeks that Kate was pregnant, St. James Palace appears to have been more or less forced to confirm the news earlier than they would have wanted because on Monday the duchess was admitted to the hospital, an event that was sure to have reporters on both sides of the Atlantic speculating. The official reason for her trip to the hospital: hyperemesis gravidarum. What the heck is that? Basically, a severe form of morning sickness.

Here we’ll let the U.S. National Library of Medicine explain:

Hyperemesis gravidarum is extreme, persistent nausea and vomiting during pregnancy that may lead to dehydration. …

Nearly all women have some nausea or vomiting, or “morning sickness,” particularly during the first 3 months of pregnancy. The cause of nausea and vomiting during pregnancy is believed to be rapidly rising blood levels of a hormone called HCG (human chorionic gonadotropin), which is released by the placenta.

Extreme nausea and vomiting during pregnancy can happen if you are pregnant with twins (or more) or if you have a hydatidiform mole.

And that last thing we can’t pronounce?

A hydatidiform mole is a rare mass or growth that forms inside the uterus at the beginning of a pregnancy. It is a type of gestational trophoblastic disease (GTD).

Kate is expected to stay in the hospital for several days and will likely be put on some form of bed rest afterward. In the meantime, let the speculation about the twins (or more!) begin.