Jennifer Lopez was performing and her costume appeared to reveal a bump.
An onlooker told the New York Post, "A definitive baby bump was there. She was very quick to push down her top. Then she talked about how this year is full of firsts for her… and every so often her dress would fly up and you would see her belly."
The Do It Well singer has denied reports that she is pregnant.
But a source told The Sun, "She will announce that she and Marc Anthony are expecting their first child on Saturday night at her Madison Square Garden concert."
Image: Daily Mail