From the International Business Times:
The Duchess of Cambridge’s condition was revealed after she checked into King Edward VII Hospital to be treated for acute morning sickness. The royal family confirmed the pregnancy in a statement on Monday and said Kate was about 12 weeks along.
While most pregnant women will experience nausea at some point during gestation, mostly during the first trimester, in a fraction of cases the vomiting becomes so severe that the mother must be hospitalized. This more severe form of morning sickness is known as hyperemesis gravidarum. Sometimes severe vomiting is accompanied by other symptoms, like dark urine or little urination, dizziness and vomiting blood.
Hyperemesis gravidarum can be risky if left untreated. The uncontrolled vomiting can cause severe dehydration, muscle wasting, imbalanced electrolytes and weight loss of more than 5 percent of a mother’s body weight. Other possible complications include jaundice, kidney failure and other serious adverse events, including death.