"OK, well, his name, we haven't said anything, my husband hopefully won't kill me for saying it, but his name is Rennie David Foster," she told co-hosts Hoda Kotb and Jenna Bush Hager during a virtual chat, which will air on March 19. "We picked Rennie because I had actually been in labor for a while, we didn't have a name picked out."
McPhee explained that, at the time, Foster was on a text chain with his sisters, one of who suggested an "old family name."
"It was his great-grandfather's name, his great-uncle's name," she explained, "so it has a long history in his family. My husband said, 'Hi, Ren Foster,' and so we said, 'That's a good name. It's a strong name.'"
In early March, McPhee, 36, shared their first photo of her newborn son. "Just in case you were wondering, I love being a mommy," she wrote alongside a photo with her baby boy.
A source also shared insight on McPhee and Foster's first few weeks with their son. "Katharine, David and the baby are all doing great," the insider told E! News in early March. "Katharine is so excited that the baby is finally here. She had been waiting to be a mom for a long time, and couldn't be any happier that the time has come."
Another source also added that McPhee, who tied the knot with Foster in 2019, is having a "wonderful" time as a new mother. While this was the first child for McPhee, Foster is also dad to five daughters: Erin Foster, Amy Foster, Sara Foster, Allison Jones Foster and Jordan Foster.
(E! and NBC are both part of the NBCUniversal family.)