Les Femmes Enceintes Devant le Tribunal Révolutionnaire is an amazing resource if you are interested in the processes of the Tribunal during the Terror and the treatment of prisoners in the prisons. I came across it while researching the story of Princesse Joseph de Monaco and found it packed with information about what actually happened to female prisoners who claimed to be pregnant, including, rather unpleasant details of the horrible internal examinations that they were forced to undergo in the presence of a doctor and a midwife.
I had had a romantic idea that they were left to their own devices and, like Rosalie Lubomirska, only turfed out when they failed to appear pregnant over a period of time but no, this really was a matter of life or death and was treated very seriously by the authorities.
Despite the unpleasantness though, it was clearly worth taking a gamble. If the Princesse Joseph de Monaco had managed to keep up the pretence for just one more day then she would have saved her life.