Middleton And Prince William
Queen Elizabeth recently decreed that if Prince William and wife Kate's first child is a girl, she will be granted the title of "princess." Reuters

Excitement has been predictably high since news first hit on Monday that the Duchess of Cambridge, Kate Middleton, is pregnant, but new details about the medical condition the Duchess is suffering from could suggest that royalists will have even more to cheer about.

According to medical experts the condition Middleton is being hospitalized for, Hyperemesis Gravidarum, is a dangerous type of morning sickness that could be an indication the Duchess is pregnant with twins.

"Their Royal Highnesses the Duke and Duchess of Cambridge are very pleased to announce that the Duchess of Cambridge is expecting a baby," a rep for St. James’ Palace announced on Monday. "The Queen, the Duke of Edinburgh, the Prince of Wales, the Duchess of Cornwall and Prince Harry and members of both families are delighted with the news."

"The Duchess was admitted this afternoon to King Edward VII Hospital in Central London with Hyperemesis Gravidarum," the palace continued in a statement. "As the pregnancy is in its very early stages, Her Royal Highness is expected to stay in hospital for several days and will require a period of rest thereafter."

The potentially dangerous condition, characterized by severe vomiting that results in dehydration, reportedly affects only 2 percent of pregnant women, and less than 1 percent are ever hospitalized for it. Ashley Roman, an obstetrician and maternal-fetal medicine specialist at NYU’s Langone Medical Center, told ABC News that a study conducted on the condition found that women pregnant with multiple babies have an elevated chance of experiencing Hyperemesis Gravidarum; 7.5 percent higher than women pregnant with only one child.

The condition is also more likely to appear in women who are young, pregnant for the first time, and non-smokers. Roman added that the condition wasn’t likely to affect the health of the fetus and in most cases, the symptoms tended to resolve within 16 to 20 weeks into pregnancy. However, Roman added that in some rare cases the symptoms persisted throughout the entire duration of the pregnancy.

It’s not known exactly how far along Middleton’s pregnancy is, but Middleton is thought to be less than three months pregnant, because the palace suggested she had originally been planning to make an announcement at around that milestone.

Both the Duke and Duchess of Cambridge are 30; the child will be the first for both of them. While the palace has not released any official updates on Middleton's condition, Prince William was photographed by CBS visiting Middleton on her second day in the hospital.