It may sound unbelievable to you but its true, its very rare fewer than 300 cases have been noted in 400 years of medical literature.
In Zahra case The doctors took out a calcified mass which bared a remarkably resemblance to a mummy. In order to protect itself, the mother’s organism encased the foetus in a calciferous substance so that the immune system does not start a reaction.
In 1955 a 26 year old woman named Zahra Aboutalib was rushed to the hospital to deliver her baby, but after and excruciating 48 hour labor, she still could not deliver the baby so she had to undergo a caesarean section but the thought of dieing in child labor terrified the woman and urged her to flee the hospital and hide in her home. After doing so, she gave birth nearly 50 years later to a mummy baby.
There is a specific term for this called Lithopedion is better known as a stone baby.
It is a rare phenomenon which occurs most commonly when a fetus dies during an abdominal pregnancy, is too large to be reabsorbed by the body, and calcifies on the outside, shielding the mother's body from the dead tissue of the baby and preventing infection.(wiki)
Here below picture of another case of 92-year-old woman who delivered a child (albeit not a live baby)