"There's been an outpouring of support for the couple that made them feel, perhaps, a little bit more positive about the whole thing," said Victoria Murphy, a royal correspondent with the Daily Mirror.
William left King Edward VII Hospital at around 5:45 p.m. local time Tuesday after spending more than six hours at Kate's bedside. He appeared more relaxed than he did Monday, when Kate was admitted.
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"The Duchess of Cambridge is continuing to feel better," a St. James Palace spokesman said Monday. "She and the duke are immensely grateful for the good wishes they have received. She will remain in hospital at present and will continue to be treated for hyperemesis gravidarum."
William can relax, as Kate seems to be in good hands -- she is reportedly being treated by the queen's doctors. The couple is set to move into a newly renovated Kensington Palace early next year, which might make the pregnancy easier.
Kate's parents, Carole and Michael Middleton, were spotted leaving their home in Bucklebury Tuesday. They will reportedly make the 50-mile trek to London to visit their daughter. Other than William, no other member of the royal family has been spotted entering or leaving the hospital.
Speculation is still in overdrive on exactly how far along the pregnancy is, as the palace would not comment.
"The royal family would not normally want to announce a pregnancy before the 12-week mark, and we understand it's quite a substantial way before the 12-week mark," said Murphy. "We believe she's about seven to eight weeks pregnant at the moment."
ABC News' Sydney Lupkin, Carolyn Durand, Amanda Keegan and Kelly Hagan contributed to this report.