Mary Hendershot was an unwitting part of experiments to birth alien fetuses.
Hendershot came to believe that she had become pregnant from an alien abduction, and was seen by Dr. Lev at Zeus Genetics. When the time approached to have the baby delivered, she became extremely concerned and left the facility. She found Dana Scully to warn her about what was happening. She went with Skully to a different facility, Walden Freeman Army Hospital, to deliver the baby. However, Skully realized they were being deceived and tried to get Hendershot out. They were supposedly rescued by Knowle Rohrer and a team, but Hendershot delivered the baby during the escape and came unconscious. She woke in a different hospital and given her healthy baby. Skully, however, believed it was not the one delivered. (TXF: "Per Manum")