Kourtney, 34, who has two children with partner Scott Disick, wanted to make sure that Kim should be aware of the changes she is about to experience after giving birth on June 15, reported Hollywood Life.
"(Kim) has no idea what she's in for as a mom. (She told Kim) her life is going to completely change and she's going to be totally surprised at everything. Kim is about to be shocked at all the changes, and Kourtney knows this because she has been going through it for years," a source said.
"Even though we're sure Kourtney is ecstatic for Kim and Kanye, the insider also said Kourtney has said Kim isn't prepared for the totally change her life will be," the source added.