Researchers have discovered the world’s first-known pregnant mummy, dating from the first century in Egypt. The find was unexpected, as inscriptions on the mummy’s coffin suggested the remains inside belonged to a male priest, according to a new study.

The mummy was donated to the University of Warsaw in Poland in 1826; only recently did archaeologists with the Warsaw Mummy Project conduct a detailed analysis of the mummy while studying the National Museum in Warsaw’s collection of animal and human mummies.