Phantom pregnancy is a well known condition which can make a woman not only convinced she is expecting, but can also fool her body into thinking she is, too. It most often occurs in women in their 30s and 40s who desperately long to have a child.
But doctors are baffled by the case of a woman in Brazil who arrived at hospital with sharp pains and a large bump.
When the 37-year-old showed them proof of her pre-natal treatment, they believed that her labour was real and checked for signs of the baby's heartbeat.
When they couldn't detect one, they immediately performed an emergency Caesarean - only to find there was no baby in the woman's womb.
Rosalice Almeida, the hospital's director in Cabo Frio, south-east Brazil, told the country's Globo G1 website: "She'd done her whole pre-natal and was already overdue. Because the doctors couldn't pick up the heartbeat, they decided there wasn't time to request an ultrasound.
"They did the surgery then had the great shock of not finding any baby at all."
The woman's husband, 23, told doctors this was the second 'pregnancy' his wife had in a year.
Last year she claimed she got pregnant only to go the hospital and lose the child, but she never showed him a death certificate. The case was registered as a phantom, or false pregnancy.
The rare condition occurs when a non-pregnant woman convinces herself she is pregnant, often even exhibiting all the classic symptoms of pregnancy. She was released from the hospital and referred to psychiatric care.