By Lisa Flam, NBC News
With the bombshell news that Duchess Kate is pregnant with a royal heir and has been hospitalized with a rare pregnancy complication called hyperemesis gravidarum, there is one thing that Ann Marie King wants to make clear.
"This is not morning sickness," says King, who suffered from the condition during her pregnancy and later started a support group for sufferers. "This is times a thousand morning sickness."
"Everything makes you sick," she added. "It's like your senses are multiplied by 1,000. Even movement can make you sick, like trying to get out of bed. It's debilitating."
Hyperemesis gravidarum (HG) is vomiting during pregnancy that is so excessive that women can become dehydrated and start to lose weight because of inadequate nutrition, said Dr. Amos Grunebaum, director of obstetrics at New York Presbyterian/Weill Cornell Medical Center. If not treated properly with intravenous fluids and anti-nausea medicine, it can be life-threatening to pregnant women and their fetuses, he said.
"Morning sickness is normal," he said. "Hyperemesis gravidarum is not."
"Women with hyperemesis gravidarum are sick, they're physically sick and they need to be taken care of," Grunebaum said. "They need medication and often they need to get admitted to get hydrated," though some women can be treated at home.
Grunebaum said about half of 1 percent of American pregnant women suffer from the condition. The American Journal of Perinatology says it strikes roughly two percent of pregnant women. "We don't know the cause," said Grunebaum, a maternal-fetal medicine specialist. "It's very rare."
The condition is related to the pregnancy hormone human chorionic gonadotropin, or HCG, which increases in early pregnancy. Hyperemesis gravidarum usually starts early in pregnancy, peaking in severity around week 12. It's not known why it makes some women so sick, he said.
"Some women react to it more than others," he said of the hormone. Because women carrying more than one fetus produce more HCG, they are more likely to develop hyperemesis gravidarum, as are women whose mothers had the condition, he said.
The condition has been around for a long time. Author Charlotte Bronte is thought to have died from it after a four-month bout of extreme nausea that left her dehydrated and emaciated. Today, there's still no cure for HG, but it can be treated using a variety of medications, including some super-strong anti-nausea drugs developed for chemotherapy patients.
Because the condition is so easily treated, only in very rare cases is it life-threatening, Dr. Peter Bernstein, a maternal-fetal medicine specialist at Montefiore Medical Center in New York.
"It's an extremely uncomfortable and unpleasant condition but it's not typically dangerous," he said.
And as bad as it can be, HG can be the mark of a healthy pregnancy.
"It's a sign that the placenta is making more hormones," he said. "The mother may be miserable but [she's] less likely to have a miscarriage."
While Kate-watchers may be quick to think she's carrying more than one heir, simply having hyperemesis gravidarum is not a sign that a woman is carrying twins, Bernstein said. "We see it commonly in women carrying singletons," he said.
King suffered from hyperemesis gravidarum for her entire pregnancy and required a feeding tube and several hospitalizations. During that awful time, she found no fellow sufferers or resources to help her.
After King gave birth to a healthy boy in 2003, she co-founded the HER Foundation, an education and research group dedicated to HG.
King believes the numbers are much higher than the estimated 1 to 2 percent of women affected by the condition.
The condition is not always diagnosed, King said, adding that she hopes news of Kate's hospitalization, though an unfortunate development, will raise awareness worldwide.
"Hopefully it will educate the public and these women will start being treated seriously," King says. "Pregnancy should be the happiest time. But you just feel like you're dying. You can't control it."
One thing women suffering from HG or extreme morning sickness don't want to hear is to try saltines, which are often recommended for more typical, milder nausea and vomiting.
"'Just try some crackers,' that's one of the worst things we like to hear," King said.