Duchess Kate hospitalized for hyperemesis gravidarum: What is it? Hyperemesis gravidarum, the type of morning sickness that Duchess of Cambridge is hospitalized with, is rarer than the condition that's experienced by many pregnant women, according to experts. In a statement Monday, palace officials said Duchess Kate was hospitalized with hyperemesis gravidarum, an extreme, potentially dangerous type of morning sickness where vomiting is so severe that no food or liquid can be kept down. Palace officials, who announced the upcoming birth of the first child between the duchess and Prince William, said the 30-year-old is expected to remain hospitalized for several days and would require a period of rest afterwards. The announcement has put the spotlight on the rare pregnancy complication. "It's not unusual for pregnant women to get morning sickness, but when it gets to the point where you're dehydrated, losing weight or vomiting so much you begin to build up (toxic) products in your blood, that's a concern," said Dr. Kecia Gaither, director of maternal fetal medicine at Brookdale University and Medical Center in New York. Nearly all women have some morning sickness during the first three months of pregnancy, according to the National Institutes of Health, which is caused by rising levels of the HCG hormone, which is released by the placenta. However hyperemesis gravidarum is thought to affect about one in 50 pregnant women, and tends to be more common in young women, women who are pregnant for the first time, those expecting multiple babies, non-smokers and women with a hydatidiform mole, a rare growth that forms inside the uterus at the beginning of pregnancy. Gaither said that fewer than one percent of women with the condition need to be hospitalized. Doctors aren't sure what causes it but suspect it could be linked to hormonal changes or nutritional problems. Women admitted to the hospital with hyperemesis gravidarum are usually treated with nutritional supplements and given fluids intravenously to treat dehydration. Dr. Dagni Rajasingam, a spokeswoman for the Royal College of Obstetricians and Gynaecologists, said most women hospitalized with the condition are discharged within several days. "It depends on how well the woman is keeping fluids down," she said. 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. A pregnant woman may be diagnosed with the condition if she vomits more than four times per day -- so much so that she loses more than 10 pounds - or feels dizzy, lightheaded, or dehydrated from vomiting, according to the Cleveland Clinic. Gaither said the condition usually subsides by the second trimester. "The rest of the pregnancy could be entirely uneventful," she said, adding that pregnant women treated for the condition are usually advised to avoid fatty foods that could aggravate the problem. Gaither said the duchess would probably be able to meet her usual royal obligations by her second trimester. "She should be able to meet all her public obligations soon," she said, advising her to take her vitamins and ensure there are no other underlying health problems. She should just be looking forward to having a healthy little plump person.