In the womb of a 2,000-year-old ancient Egyptian mummy, researchers have discovered a fetus that’s been surprisingly well-preserved like a “pickle”.

The incredible discovery of the first known pregnant Egyptian mummy was presented by a team from the Warsaw Mummy Project last year. Intrigued by this so-called “Mysterious Lady,” the researchers used CT scans to get a deeper look inside this unique mummy. 

“[There is] No other case of a pregnant ancient mummy, especially no such case from Egypt, that the scientific community knows of,” Dr Wojciech Ejsmond from the Polish Academy of Sciences and lead author of the research told IFLScience, so there is much to learn here. 

From the CT scans, they found further evidence that the body’s pelvis cavity contained a fetus. But the question remained, how did the fetus remain intact after 2,000 years? In a new paper in the Journal of Archaeological Science, the team explained that the fetus was preserved in a very similar way to “bog bodies.”

Bog bodies are human cadavers that have been naturally mummified in the highly acidic and low oxygen environment of a peat bog. It appears that a similar process occurs to a fetus that’s left inside a mummy preserved using traditional ancient Egyptian embalming processes. The pH of blood in a person naturally falls significantly after death, becoming significantly more acidic with concentrations of ammonia and formic acid increasing over time. Further, the fetus is hermetically sealed inside the womb, similar to the hypoxic (low oxygen) conditions of a peat bog. 

“The fetus remained in the untouched uterus and began to, let's say, ‘pickle.’ It is not the most aesthetic comparison, but conveys the idea,” the Warsaw Mummy Project said in a blog post. 

Just like a bog body, the outside of the fetus is remarkably well-preserved, but their bones have almost completely disappeared. This is because the bone undergoes a process of demineralization in a highly acidic environment. However, since the fetus doesn’t have any hint of bones — a key feature that’s often picked up on X-rays and other scans — it had previously not been spotted. 

“Usually, researchers are looking for bones when examining X-rays and CTs,” Dr Ejsmond told IFLScience.

“We had very high-quality equipment for our research, which allowed us to see many details,” he added. “Our research showed that fetuses may have very poorly preserved bones due to specific taphonomic processes that took place during embalming, and thus may not be visible in CTs and X-rays.”

This raises some interesting possibilities. Since conventional techniques would not have picked up on the fetus, this means that it's possible there could be other ancient mummies in other museum collections that also died with unborn children still intact throughout the ages. 

“We've been contacted by some scholars who think that the mummies that they found or are researching may be pregnant," Dr Ejsmond said. " We will see about that and study more mummies. For sure, there are more such cases, but so far people are not focussing on this."

In the meantime, this remains the only known pregnant mummy, and presents more questions than can be currently answered: why was the mummy's fetus left but other organs removed, was this a rare practice, and what does this mean for Egyptian views of the afterlife in regards to children?