‘Pregnancy test’ for skeletons could help reveal ancient mothers

Researchers are making strides towards developing a pregnancy test for women from centuries past.

This groundbreaking investigation has revealed the presence of oestrogen, progesterone, and testosterone in the skeletal remains of women dating from the 1st to the 19th century AD, including some who were buried alongside fetuses. Such findings indicate that old bones and teeth retain discernible traces of specific sex hormones, potentially aiding in the identification of individuals at archaeological sites who were pregnant or had recently given birth, according to Aimée Barlow from the University of Sheffield in the UK.

“The deep emotional and physiological experiences surrounding pregnancy and childbirth are significant to women, yet they have largely gone unrecorded in archaeology,” she explains. “This innovative technique stands to transform our understanding of the reproductive histories of ancient societies. I am genuinely excited about it.”

Tracing pregnancy in historical individuals proves challenging, particularly when the fetus is too young to have formed a skeleton. Even fetuses from the second or third trimester can be difficult to identify since their bones may closely resemble those of the mother’s hands, often placed over their abdomen during burial.

Contemporary pregnancy tests analyze hormone levels such as hCG in blood or urine, but hCG degrades rapidly, leaving little trace behind.

In contrast, progesterone, oestrogen, and testosterone can persist in body tissues for longer periods. Previous studies demonstrate that these steroid hormones can be detected in blood, saliva, and even hair – including ancient strands from Egyptian mummies.

To explore the possibility of detecting ancient pregnancies, Barlow and her team collected samples from rib fragments and one neck bone of two men and seven women buried in four English cemeteries. They also examined the teeth of an additional man.

Among the women, two had verified fetal remains in their bodies, while two others were interred with newborns. The sexes of other individuals were determined through DNA analysis.

The research team ground each sample into a powder and employed various chemicals and techniques to extract any steroid hormones. Subsequent laboratory analyses revealed the concentrations of oestrogen, progesterone, and testosterone in the 74 samples tested.

Oestrogen was identified in only four samples, without a consistent pattern – this may be attributed to its quicker breakdown rate compared to progesterone and testosterone, making it less reliable for preservation in tissues.

In contrast, progesterone levels were particularly elevated in the vertebrae of a young woman who died carrying a full-term fetus in the 11th to 14th centuries. Another third-trimester woman from the 18th or 19th century exhibited high progesterone levels in her rib, while moderate levels were found in the dental plaque of women buried with infants in the 5th or 6th centuries.

Interestingly, these four women showed no detectable testosterone in their bones or teeth, although one buried with a premature baby had a slight presence in her plaque. Conversely, the three women buried without any fetal or infant associations, interred in an 8th to 12th-century cemetery and a Roman-era grave, did exhibit testosterone in their ribs and teeth.

Low levels of testosterone are important for women’s health, making its detection in these samples expected, Barlow notes. “However, the absence of testosterone may suggest a recent or ongoing pregnancy at death,” she added.

According to Alexander Comninos from Imperial College London, “This is a fascinating and unprecedented confluence of archaeology and hormone science. These methodologies could facilitate more reliable detection of pregnancy in skeletal remains, yielding deeper insights into ancient pregnancy experiences.”

Nonetheless, despite the encouraging results, Barlow emphasizes the need for further investigation to clarify the nuances. For instance, men’s bones and inner teeth often demonstrate moderate progesterone levels for reasons that remain unclear, she explains. “We approach interpretations with great caution at this stage.”