Cartman's Mom is Still a Dirty Slut (2) - S2-E2
Corrected entry: When Mrs. Cartman goes in to ask for an abortion, the person at the counter claims that Cartman, at eight years old, is in the "fortieth trimester." Since a trimester is about three months long, 40 would mean about 10 years since conception, or a child of about 9 years and 3 months. An eight-year-old, plus three trimesters of development, would actually be in the thirty-fifth trimester.
Correction: It was a rough estimation.