Have you ever heard a story about a woman who goes to her doctor for a routine checkup only to find out she is pregnant and wonder how something like that could go unnoticed? Thanks to advancements in modern medicine, accidental medical discoveries are few and far between. However, it is still possible for doctors and surgeons to stumble upon an abnormality without meaning to. For example, the surgeons who went to perform a Cesarean section and found no baby, or a man who saw his doctor to be treated for stomach pain and found out he was actually a woman. Here are four unbelievable medical cases that were discovered by accident:

1. Surgeons Find 9-Pound Baby Inside Woman Who Was Having Her Ovaries Removed

After severe bouts of stomach pain that had lasted a couple of months, 25-year-old Rebecca Oldham underwent two blood tests, three scans, and six pregnancy tests to no avail. In hopes of alleviating her agonizing cramps, Oldham had surgery scheduled to remove her ovaries, but during the operation doctors discovered the actual root of her pain: a 9-pound baby at 36 weeks. Doctors say the baby was not detected during all the usual pregnancy tests due to its positioning inside of her womb. Although surprised, Oldham turned out to be excited over the discovery, since she had long been under the impression that she was unable to become pregnant.

2. Man Goes To His Doctor To Be Treated For Stomach Pain And Finds Out He’s A Woman

Doctors at First People’s Hospital of Yongkang, China, were positive a 44-year-old patient was a man due to his appearance, and so did he. The married man from Zhejiang went in to be treated for stomach pain and blood in his urine, but ended up finding out he was on his period. As doctors noted, the man had a deformed penis.

A CT scan also showed female reproductive organs, including a uterus and ovaries. Further blood test results and a chromosome examination revealed the man had two X chromosomes, meaning he is genetically a woman. The doctors diagnosed the man with congenital adrenal hyperplasia, a genetic disease that causes swelling in the adrenal glands as the result of a decrease in stress hormones and an increase in male sex hormones, which caused him to look like a man.

3. 40-Year-Old Fetus Discovered In 82-Year-Old Woman

Imagine the surprise of Colombian doctors who discovered a 40-year-old calcified fetus hiding in the abdomen of an 82-year-old woman. There are only 300 recorded medical cases of lithopedion, a Greek word meaning “stone baby.” Stone babies usually occur as the result of an ectopic pregnancy where the fetus develops in the mother’s abdomen instead of the uterus. However, most ectopic pregnancies occur in the fallopian tubes. After the baby dies in the abdomen, the body works to protect itself from infection by calcifying the dead fetus. While stone babies are extremely rare, they are potentially life-threatening due to infernal hemorrhaging.

4. Doctors Performing A C-Section Find No Baby

Doctors at Cape Fear Medical Center in North Carolina were issued “letters of concern” after performing a C-section on a woman who wasn’t pregnant. The hospital’s head resident made the pregnancy diagnosis, and after two days of trying to induce labor the medical team decided on a C-section. When the doctors made the unnecessary incision only to find an empty uterus, they reportedly “closed her back up.” Although rare, pseudocyesis, also known as false or hysterical pregnancy, does happen and is usually the result of a soon-to-be-parent who is overzealous about becoming pregnant. While it is a diagnosed psychiatric condition, women with pseudocyesis often experience normal pregnancy symptoms such as swollen breast, a halt in menstruation, and stomach pain.