Doris Ayling is nearly 100 years old and has received a letter from the hospital saying she was pregnant.
Baffled Doris Ayling was given an antenatal appointment and told to provide a urine sample.
The mum of three, whose children are pensioners, says her correct date of birth was on the letter from Fareham Community Hospital in Hampshire.
Portsmouth Hospitals NHS Trust admitted the blunder and apologised to her son Brian, 76.
Former school cook Doris, of Bognor Regis, West Sussex, said: “I’m almost 100 so how can I be expecting? But Doris took hospital blunder in good humour.
“I have three children and 20 grandchildren but I haven’t been pregnant for 70 years.”
A hospital trust spokesman said: “It was a rare administrative error and we have apologised for any unnecessary anxiety this may have caused.”