Is she pregnant?这个英语笑话怎么理解?

Is she pregnant?这个英语笑话怎么理解?A woman went to the doctor's office where she was seen by one of the new doctors ...but after 4 minutes in the examination room,she burst out,screaming as she ran down the hall.An older doctor stopped her and asked what the problem was,and she told him her story.After listening,he had her sit down and relax in another room.The older doctor marched down the hallway to the back where the first doctor was and demanded,"What's the matter with you?Mrs.Terry is 63 years old,she has four grown children and seven grandchildren,and you told her she was pregnant?" The new doctor continued to write on his clipboard and without looking up said,"Does she still have the hiccups?"哪点好笑?打嗝跟怀孕,