Prince William arriving at King Edward 7th Hospital in London on December 4, 2012. Credit: XPOSUREPHOTOS.COM

What a prince!

On Tuesday, Dec. 4, Prince William returned to Kate Middleton's side at London's King Edward VII hospital, where the pregnant Duchess, 30, was admitted Dec. 3 for hyperemesis gravidarum, an acute form of morning sickness. (Less than 1% of pregnant women suffer from the condition, which can cause severe nausea, vomiting, weight loss, dehydration, lightheadedness and fainting.)

Wearing a purple sweater, pale-blue collared shirt and dark jeans, the doting dad-to-be, 30, arrived at the hospital just before noon and headed directly inside to be with his wife.

A palace spokesperson confirmed to Us Weekly that Middleton's condition will be monitored closely at the hospital for the next several days, after which time she will be released and require a period of rest. (On Monday, the mom-to-be canceled three upcoming public appearances to accommodate her recovery.)

The Duke, meanwhile, will "continue the current tour of duty with the Search and Rescue Force" through next summer, a rep told E! News, but the health of his wife and unborn child remain a top concern.

"Trying for a baby has been their priority," a royal confidant told Us just prior to the couple's Dec. 3 announcement. "They're both excited to be focusing on a new chapter in their lives."