Karoline Leavitt announced on social media Thursday that Viviana, or "Vivi," joined her family on May 1.
Leavitt and her husband, Nicholas Riccio, have an older son, Nicholas (or "Niko").
"She is perfect and healthy, and her big brother is joyfully adjusting to life with his new baby sister," Leavitt wrote in the post, which also included a photo of her with Vivi in her nursery. "We are enjoying every moment in our blissful newborn bubble."
Leavitt has not indicated publicly how long she will take for her maternity leave. Other administration officials are expected to take the White House briefing room lectern in Leavitt's absence; Secretary of State Marco Rubio, who doubles as the president's national security adviser, held a press briefing at the White House earlier this week.