The Harpers previously welcomed son Krew Aron - whom Bryce honors on his headband underneath his helmet - to the world in August 2019.
The couple announced they were expecting baby No. 2 in July, just before the 2020 MLB season got underway.
Harper just completed Year 2 of a 13-year, $330-million contract with the Phillies. He hit .268/.420/.542 with 13 home runs and 33 RBIs while leading the majors with 49 walks in 58 games this summer.