She doesn't. She suspects that she might be, but it later turns out to have been a false alarm.
At one point in the story, she tells Kenickie he's not the father, but it's strongly implied that she's lying to him because she's mad at him and that, despite her "reputation", Kenickie is the only boy she's actually had sex with.
it is my understanding that Rizzo was the girl who got pregnant in Grease.
Risso. Risso.
in a ferris wheel
it was Marty who spread the rumour in the Drive-in scene shortly after Rizzo tol her. hope this helps
ferris wheel
Rizzo from Grease? She's at school on the last day where they are having the carnival thing on the track & she yells down to Kenickie from the ferris wheel
It was Marty that spread the rumour Rizzo was pregnant
Rizzo
Rizzo
PBR
Rizzo
Rizzo