Amber Portwood learned of Gary Shirley's baby news during filming on Teen Mom OG.

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In a sneak peek at the MTV reality series' April 13 episode, Shirley arrives to Portwood's home, where he fills her in on his and Kristina Anderson's exciting news.

“I just wanted to tell you something before you hear it from Leah,” Shirley tells Portwood in the sneak peek, which was shared by Wetpaint Entertainment on Thursday.

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Shirley began dating Anderson last year, and the pair revealed they were expecting several months later.

“Are you and Kristina getting married or something?” Portwood asks.

“Not for a while, if ever,” Shirley replies, explaining he and Anderson are “having a baby.”

“Kristina is pregnant and before Leah said anything I wanted to tell you,” Shirley explains. “So Leah is going to have a little brother or sister.”

As Shirley and Anderson prepare for the arrival of their baby girl, Portwood is busy planning her wedding to fiancé Matthew Baier, taking college classes and spending time with her and Shirley's daughter, 6-year-old Leah.

As fans of Teen Mom OG saw in the trailer, Baier proposed to Portwood during filming after several months of dating.

For more of Amber Portwood and Gary Shirley, tune into Teen Mom OG on Mondays at 10 p.m. on MTV.