Her growing bundle of joy may be causing Kate Middleton a bundle of pain just about now.

"Groin sensitivity caused by the stretching of the round ligaments that surround the uterus is very common in the second trimester," said Dr. Jennifer Ashton, ABC News senior medical contributor and a practicing OB-GYN. "This is normal pain, especially during a first pregnancy, because those ligaments are being stretched in ways they never have been before."

A pregnant Kate might feel a stabbing pain on one or both sides of the abdomen. The pain can be so severe that some women mistake it for appendicitis. While a discussion with the doctor is definitely in order, Ashton said the only thing that will ease round ligament discomfort is time and Tylenol.