Like Kate, William's mother, Diana, also reportedly suffered from morning sickness for months, and was the subject of constant media attention after she became pregnant just four months after her wedding to Prince Charles.
"The whole world is watching my stomach," Diana once said.
According to Britain's Department of Health, severe morning sickness most often affects women early in their pregnancy, and is more common in young women, women who are pregnant for the first time and those expecting multiple babies.
Dr. Daghni Rajasingam, a spokeswoman for Britain's Royal College of Obstetricians and Gynaecologists, said women with severe symptoms -- including dehydration, dizziness and persistent vomiting -- need to be hospitalized for treatment, including being given fluids intravenously.
"However, this usually only means a few days in (the) hospital," she said in a statement. "The best advice for anyone suffering from (severe morning sickness) is to get plenty of rest and drink lots of fluid."
William is second in line to the throne after his father, Prince Charles, so the couple's first child would normally become a monarch - eventually.
The confirmation of Kate's pregnancy caps a jam-packed year of highs and lows for the young royals, who were married in a lavish ceremony at Westminster Abbey last year.
They have travelled the world extensively as part of Queen Elizabeth II's Diamond Jubilee celebrations and weathered the embarrassment of a nude photos scandal, after a tabloid published topless images of the duchess.
