9,000-Year-Old Remains of Pregnant Woman With Remarkably Preserved Fetus Found in Sweden

Ancient remains on Lilla Karlsö

A tragedy has remained concealed for millennia inside a secluded cave on a small Swedish island.

Beneath layers of ancient sediment, archaeologists have uncovered the bones of a young woman and a fetus thought to have been at around 32 to 34 weeks of gestation.

The remarkable find came from Suder Vagnhus cave on Lilla Karlsö, an uninhabited Baltic Sea nature reserve off the coast of Gotland.

If the archaeologists’ estimates prove accurate, the bones may have remained there for between 8,000 and 9,500 years.

That would place the discovery among the oldest known burials of a pregnant woman whose fetal remains are still in situ.

The woman and fetus may not be the island’s sole archaeological discovery. Although only wildlife now lives on Lilla Karlsö, evidence indicates that they may not have been interred there alone.

"We do have one or possibly two more individuals identified in the cave (at least one young child), though only from a few individual bone elements, indicating that the cave had been used as a burial site or something similar," archaeologist Alexander Sjöstrand of Uppsala University in Sweden told ScienceAlert.

"This also corresponds with the sister island of Stora Karlsö and cave Stora Förvar, where they had approximately 15 individuals from the same time period in a similar cave excavated during the late 1880s."

Sjöstrand holding the fetus’s parietal skull bone. (Alexander Roesen Sjöstrand/Uppsala University)

Suder Vagnhus cave and its hidden chamber

The entrance to Suder Vagnhus has long been familiar. Positioned above sea level on the island’s shoreline, its 18 by 18-metre opening looks out over the Baltic Sea like a huge, hollow eye socket.

A hidden feature was found in 1992, however. At the base of the eastern wall, obscured by rubble, was a narrow opening into a side cave, only large enough for a person to squeeze through.

The first exploration revealed a small cavern containing numerous animal bones. Radiocarbon dating of one sheep skull placed it in the 14th century, indicating that the chamber might have remained untouched for roughly 700 years.

The entrance was sealed again with limestone blocks to keep out animals and inquisitive visitors. It remained closed until Sjöstrand and his colleagues began excavating the site in 2023.

The remains were found within this concealed side chamber.

The arrangement of the minute bones gave archaeologists little reason to doubt that the woman had been pregnant at the time of burial.

Some of the recovered fetal bones, together with further fragments that probably belonged to the woman. The fetus’s arm has been partially reconstructed on the left. (Alexander Roesen Sjöstrand/Uppsala University)

"The fetus was located in the abdominal area with some of the mother's ribs found strongly indicating the fetus was inside," Sjöstrand told ScienceAlert.

"The fetus is also positioned head towards the mother's feet, and as far as we've been able to tell on the mother's position, face towards the spine, which aligns with the age of the fetus having turned in the stomach, getting ready for birth."

The woman seems to have been a teenager, aged around 14 to 19. The bones recovered so far indicate that she may have been laid to rest in the “Hocker” position, curled on her side. Sjöstrand said this posture matches burials typical of the period and supports the interpretation that she was deliberately buried.

Because the fetal bones were exceptionally well preserved, researchers could measure them, especially the long bones. Their dimensions are consistent with development during the third trimester.

It remains unclear how the woman died, or whether her pregnancy played any part in her death.

"We have some thoughts on it, but it's to early to speculate publicly," Sjöstrand said.

The woman’s rib, labelled “mother’s rib”, and the fetus’s skull fragment, labelled “fetal skull”, as they were found during excavations in the cave. (Alexander Roesen Sjöstrand/Uppsala University)

Why pregnant woman burials with fetal remains are rare

Pregnant women’s remains containing fetuses are uncommon in the archaeological record, despite pregnancy and childbirth having posed dangers throughout much of human history.

One important explanation is that human remains themselves are relatively scarce: only a tiny proportion of any living population becomes part of the archaeological record. Organic matter, including bone, readily decomposes.

Smaller and more fragile bones have an even lower chance of surviving.

"Fetus and infant bones are very small and very fragile; there aren't that many places in the world where the environment in which the bones are buried is conducive to preservation, especially for anything close to this timeframe," Sjöstrand explained.

Another possible reason is that many maternal deaths took place during childbirth. In such cases, a baby may have survived or been buried separately.

The excavated side-cave entrance, with Sjöstrand inside carrying out the dig. (Alexander Roesen Sjöstrand/Uppsala University)

In rare instances, a pregnant woman can seem to give birth after her death. This phenomenon, known as coffin birth, happens when decomposition gases accumulate within the body and force the fetus out.

A burial more than 8,000 years old in which the fetus remains inside the mother’s body could therefore be an especially significant discovery.

"From what I've found so far, it's not unheard of to find pregnant women, but it's quite rare," Sjöstrand said.

"Cases that are 8,000 years and older are extremely rare, with only a few examples where the fetus is well preserved. So this find seems to be one of the few finds of this type and quality."

Further research will be required to establish a precise date.

At present, archaeologists estimate the remains to be between 7,000 and 10,000 years old, based on the cave’s stratigraphy, or rock layers, and comparisons with discoveries from neighbouring Stora Karlsö. The most probable range is 8,000 to 9,500 years.

Radiocarbon dating is expected to give a more exact age.

Related: A Fetus Was Preserved Within an Egyptian Mummy Because It 'Pickled', Scientists Say

DNA analysis may also verify a genetic link between the woman and fetus. That is before considering the remains of the other people found in the cave.

For now, excavation work is continuing. The cave sediment may still contain the most valuable information.

"The mother is fragmented but well preserved, and we still have not excavated her completely," Sjöstrand said.

"If we could find more of the hip, legs, and shoulder, that would go a long way to see her exact burial position and confirm how she was buried."

This article was fact-checked and edited by Clare Watson. Although we take pride in our process, we are only human. If you notice an error, please let us know.