The 35-year-old, who stars on the family's reality TV show "Keeping Up With The Kardashians," is expecting another baby with her long-term partner Scott Disick.
A source tells Usmagazine.com, "She is only a few months along. Kourtney looked really pretty. She had a nice flush on her cheeks. ... It was planned. (Kourtney) wants to have a handful of kids."
The couple is already parents to 4-year-old Mason and his sister Penelope, who is 23 months old.
Kourtney was among the guests at her sister's wedding to Kanye West in Florence, Italy, last month.