In 1875, the excavator Guiseppe Fiorelli found the impressions of a man and a woman along the Stabian Way. It will never be known whether they were family members, or if they were fleeing together by coincidence. The woman, who fell face down as she suffocated, had pulled up her dress in an attempt to protect her face from the falling ash. The fabric of her garment, which bunched around her waist, gave her the appearance of being pregnant, and excavators and the public quickly came to identify her as the “pregnant woman.”

Casts such as this one had been made since 1863, when the Italian excavator, Giuseppe Fiorelli was said to have invented the technique of injecting plaster gesso into the cavities found in the ground throughout the site of Pompeii. These holes were produced when the bodies of the victims decayed and left “voids” in the earth.
The cast of this woman was particularly attractive, and projected the pathos of a death so horrible for one so young and beautiful of form. Excavators soon began to use images of this cast to promote their work at the site of Pompeii. The casting process, devised at the same time photography was emerging as a popular medium, spread images of this and other casts to a public that was interested in knowing more about archaeology and the classical world. The contortions of many of the casts brought home the horrible manner of death encountered by many of the Pompeian victims, previously viewed rather dispassionately through the filter of classical purity.
For more information about the body casts from Pompeii, please see an article by Professor Eugene Dwyer, “From Fragments to Icons: Stages in the Making and Exhibiting of the Casts of Pompeian Victims, 1863-1888” in the journal, Interpreting Ceramics.
http://www.uwic.ac.uk/ICRC/issue008/articles/06.htm