Dr. James Parenti was Dana Scully's gynecologist during her first two trimesters. He was killed by Billy Miles in and was later found by Mulder and Dogget. (TXF: "Essence")
Dr. Parenti was contributing towards experiments to create babies that seemed alien but were actually other clone hybrids; the experiments were part of an effort to ensure humanity's survival of imminent alien colonization and had originally been initiated under orders from the Syndicate, a group that had been destroyed by the aliens in 1999. (TXF: "Essence", "One Son")