The 35-year-old 'Keeping With The Kardashians' star already has a son Mason, 4, and daughter Penelope, 23 months, with Disick, reported Us magazine.
"She is only a few months along. Kourtney looked really pretty. She had a nice flush on her cheeks," a source said.
During a double date with Disick, sister Khloe, and rapper French Montana in NYC, Kardashian abstained from drinking wine and sipped ginger ale instead.
"It was planned. Kourtney wants to have a handful of kids," the source added.
"They don't know the gender yet. They just want the baby to be healthy," the source said.