Kylie shared the news that her and Travis Scott had welcomed their second child on Instagram, along with a picture of what appears to be the new baby's hand captioned, "π 2/2/22." Sounds like she gave birth to the baby on February 2.
Kylie confirmed she was pregnant with baby #2 in September of last year β so she was probably around four months along at that point, and she'd been apparently dropping clues for weeks before the world found out.