Prince William is expressing concern about his wife, Kate, as she struggles with her second pregnancy.
Kate is suffering from a condition known as Hyperemesis Gravidarum or HG.
ABC News Senior Medical Contributor Dr. Jennifer Ashton told INSIDE EDITION, "It is like morning sickness, like a tornado is like a little wind. This is a very different medical and obstetric picture."
On Monday, following the big pregnancy news, William’s worry about his wife was evident, saying, "She is feeling okay, thanks. It has been tricky few days, week or so. But, obviously we are immensely thrilled it is great news. Early days, I am hoping that things settle down and she is feeling a little bit better."
Dr. Ashton said, "You can get clinical, severe dehydration, malnutrition. In some cases, kidney and liver dysfunction as well, so, this is potentially a very severe situation for a pregnant woman."
Kate's condition is so severe that it forced the royal couple to reveal her pregnancy before she has even reached the important 12-week stage.
"When it became apparent that she was not well enough to join [William] on a joint engagement today [William and Kate] have taken the difficult decision to be fully open about the pregnancy," a source close to Kate said.
Britain's Got Talent judge Amanda Holden spoke to INSIDE EDITION's Megan Alexander.
Alexander asked, "This is an early announcement. She hasn't made the 12-week mark yet, has she?"
Holden said, "No, I think she is about nine weeks. So, of course, every woman knows that it is an unfortunate thing to have to announce something like that when you are not over the 12-week safety period."
Watch More of Amanda Holden's Interview
William's brother Prince Harry will be bumped from fourth in line to the throne to fifth. He spoke about the pregnancy on Monday, saying, "It is very exciting news. I hope my sister-in-law gets better soon."
How bad can Hyperemesis Gravidarum get? One mom-to-be went on YouTube to talk about her pregnancy woes.
In one post, the woman said, “I'm 17 weeks and I still feel like I am going to die every day.”
A photo of Kate was taken on August 5 could possibly show the beginning of a baby bump.
Alexander asked, "Is this a surprise?"
Holden said, "I think it is a surprise to the U.K. because Prince George is only just celebrated his first birthday. Then of course, Prince William and Harry are very close in age. She is following a royal tradition."