Green’s Dictionary of Slang

p.g. adj.

also pee-gee
[abbr.]

pregnant.

[US](con. 1950s) Jacobs & Casey Grease II iv: You think maybe you’re p.g.?
[US]S. King Gerald’s Game (1993) 199: The fact that he hadn’t put his thing in her thing still might not mean she was safe from being what some of the girls [...] called ‘pee-gee’.