‘Pregnancy test’ for skeletons could help reveal ancient mothers

Scientists are studying a pregnancy test for women who lived hundreds or even thousands of years ago.

For the first time, researchers have discovered levels of estrogen, progesterone and testosterone in the skeletal remains of women from the 1st to 19th centuries AD, some of whom were buried with fetuses. The results show that ancient bones and teeth retain telltale traces of certain sex hormones, which could help determine which people in archaeological sites were pregnant or had just given birth when they died, he says. Aimee Barlow at the University of Sheffield in the UK.

“The physiological and emotional experiences of pregnancy, pregnancy loss and childbirth are profound for women, but until now they have remained largely invisible in the archaeological record,” she says. “This method could revolutionize the way we study the reproductive history of past populations. Frankly, I'm excited.”

Pregnancy is difficult to detect in ancient individuals, especially if the fetus did not yet have a visible skeleton. Even fetuses in the second and third trimester may be overlooked as their bones may resemble those of the mother's arms, which are often placed on the abdomen for burial.

Modern pregnancy tests measure levels of hormones such as hCG in the blood or urine. But hCG quickly disintegrates, leaving no traces of its presence in the body.

However, progesterone, estrogen and testosterone can remain in tissues longer. Recent research shows that these steroid hormones can be found in people's blood, saliva and hair – even long-buried strands of Egyptian mummies.

To evaluate the possibility of detecting early pregnancy, Barlow and her colleagues took samples of rib fragments and one neck bone from two men and seven women buried in four English cemeteries. They also took samples of the people's and a third man's teeth.

Two women were found to have fetal remains in their stomachs, and two others were buried with their newborn babies. The sex of the remaining people was determined using DNA testing.

The team ground each sample into powder and used chemicals and other methods to isolate any steroid hormones. Lab tests then determined how much estrogen, progesterone and testosterone were in each of the 74 samples.

Estrogen was detected in only four samples, with no clear pattern—possibly because it breaks down faster than progesterone and testosterone and may not be stored well in tissue.

However, progesterone was particularly high in the vertebrae of a young woman who died while carrying a full-term fetus between the 11th and 14th centuries. Another woman in her third trimester of pregnancy, buried in the 18th or 19th century, had elevated levels of progesterone in her rib. Moderate levels of progesterone were also found in the dental deposits of two women buried with their infants in the 5th or 6th century.

Remarkably, these four women had no traces of testosterone in their bones or any part of their teeth, although one of the women buried with a premature baby had small amounts of testosterone in her plaques. In contrast, in three women not associated with fetuses or infants who were buried in an 8th-12th century cemetery and a Roman-era tomb, testosterone was found in the ribs and in all layers of the teeth.

Testosterone at low levels plays an important role in women's health, so its presence in these samples is not surprising, Barlow says. “But perhaps the absence of testosterone indicates a recent or ongoing pregnancy at the time of death,” she says.

“This is a fascinating and unexpected intersection of archeology and hormone science,” says Alexander Komninos at Imperial College London. “These methods could be used to more reliably detect pregnancy in skeletal remains and thus give us a more accurate understanding of ancient pregnancy.”

While the results are promising, further research needs to clarify the details, Barlow says. Men's bones and internal teeth often show moderate levels of progesterone, for example, for reasons that remain to be understood, she said. “Interpretations are very cautious at this point.”

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