A mummy previously thought to be a male priest was revealed to be female — and she was pregnant at the time of her embalming, making "the Mysterious Lady of the National Museum in Warsaw" the world's only known mummified pregnant woman.

The Warsaw Mummy Project is an archaeological effort revisiting the collection of ancient Egyptian mummies in Warsaw's National Museum, which, for the most part, have never been studied in detail. Among the collection is the Mysterious Lady, and nonintrusive CT scans of the mummy prove "the sex of the mummy is undoubtedly female" by confirming the presence of breasts, female genitalia and a fetus located in the woman's uterus, according to the authors of the study, published April 28 in the Journal of Archaeological Science. 

"I had a little baby at home, and I didn't go to sleep one night; I worked," Marzena Ożarek-Szilke, a lead author of the paper and a Ph.D. candidate at the University of Warsaw, told The Academic Times.

"I switched on my computer, and I look at the CT scans, and I saw something weird in the pelvis," she said. "And I thought it looked like a fetus, but then another thought was that there are no fetuses in mummies at all; it couldn't be a fetus. … We started work all the next half year with CT scanning because we wanted a good visualization, a good image of this fetus."

An examination of the mummy's molars and skull indicates that the embalmed woman died when she was between 20 and 30 years old; the fetus's estimated age is between the 26th and 30th week of fetal life, since its head circumference is 25 centimeters. 

Wojciech Ejsmond, a lead author of the paper and an assistant professor at the Polish Academy of Sciences, said this discovery brought wider attention "to the overlooked issue of pregnancy, prenatal health and miscarriages in ancient times, especially in ancient Egypt."

"Maybe there are more of such mummies, but they were not reported, or maybe they were not recognized as pregnant," he said, "because not enough attention was paid to the examination of the lower abdominal area, and especially ... on researching or looking for pregnancy in ancient times, or any kind of signs of pregnancy."

Despite these concrete discoveries, the case of the Mysterious Lady remains enigmatic in many ways — including her origins.

When the coffin first arrived in Warsaw in 1826, it was thought to be made for a woman, because the coffin was very colorful and contained a soft, female-like depiction of the face; jewelry was also depicted on the neck of the person painted on the coffin. But translating hieroglyphs written on the coffin revealed that the coffin and cartonnage case, made of papyrus, linen and plaster, were made for a male, so the female mummy is clearly in the wrong coffin. 

The name on the coffin translates to Hor-Djehuty, a male name, and the coffin's inscription says he was a "scribe, priest of Horus-Thoth worshiped as a visiting deity in the Mount of Djeme, royal governor of the town of Petmiten, Hor-Djehuty, justified by voice, son of Padiamonemipet and lady of a house Tanetmin," confirming the coffin was meant for a man.

It's unclear where the Mysterious Lady came from or how she ended up in the wrong coffin. The authors speculate that the mummy might have been placed in the wrong coffin by accident in ancient times, but they also suggest, since the wrappings on the mummy's neck are partly damaged, that a robbery may have resulted in the Mysterious Lady being placed into a random coffin. The most likely culprits are 19th-century antiquity dealers known to have been searching for precious objects.

The age and original location of the coffin itself also remain uncertain, although the craftsmanship and style of the coffin and cartonnage indicate that it most likely dates to the 1st century B.C. 

Although Jan Wężyk–Rudzki, the person who acquired the coffin in Egypt, claims it came from the royal tombs in Thebes, the researchers of the current study say this information should be treated with great caution, even though an investigation of the coffin and the titles of the person mentioned in the inscription indicate that the coffin is indeed from the Theban area. 

"We need to be very careful about such statements, and very critical," Ejsmond said, "because it was happening many times in the past that people are claiming famous find spots for such objects to increase their value and their splendor. So this might be only a made-up legend just to increase the fame of this object."

Even if the coffin came from the Theban area, it currently cannot be proved that the coffin or the Mysterious Lady came from the royal tombs or the nonroyal tombs of the Theban necropolis — it's an open question, the authors said. 

The final mystery is why the fetus was left inside the womb. Though ancient Egyptian mummification evolved over time, it was customary at certain points in time to extract, embalm and then return the lungs, liver, stomach and heart of the deceased. The CT scans of the Mysterious Lady show a vertical cut through the skin of the lower left abdomen, indicating that this is how she was mummified. 

"Why was this fetus not removed from the womb when usually the internal organs were removed to make the mummy?" Ejsmond said. It remains puzzling to researchers because there are other documented cases of independently mummified stillborn children. 

One explanation might be that it was too difficult to remove the fetus without destroying it because of the thickness and hardness of the uterus; another set of explanations might be religious, though the researchers say that's largely speculation at this stage of research.  

Ancient Egyptian beliefs held that a person's name gave them their distinctiveness, and a person couldn't go to the afterlife without a name. Thus, perhaps ancient Egyptians believed that the afterlife of an unborn, unnamed child "could only have happened if it had gone to the netherworld as part of its mother," the authors wrote. Another explanation could be that ancient Egyptians didn't believe unborn children had souls, so there was no reason to mummify them.

There are no other cases, reported or published, of a pregnant mummified individual, so the case of the Mysterious Lady is the first to posit a new discussion for ancient Egyptian religious studies: Could an unborn child go to the netherworld?

The Mysterious Lady also opens new possibilities for studying pregnancy in ancient times, as the study's authors look to examine the soft tissue of the mummy to gather more information about her health, especially right before her death.

"We will see how it will go," Ejsmond said, "because this mummy has already surprised us numerous times, and so we expect she will continue to be studied."

The study, "A pregnant ancient Egyptian mummy from the 1st century BC," published April 28 in the Journal of Archaeological Science, was co-authored by Wojciech Ejsmond, Polish Academy of Sciences; Marzena Ożarek-Szilke, University of Warsaw; Marcin Jaworski and Stanisław Szilke, independent scholars in Warsaw, Poland.