The child is the first for Kardashian, 32, who still married to her estranged husband, pro basketball player Kris Humphries, and her beau, rapper Kanye West, 35. Kardashian filed for divorce 72 days after tying the knot with Humphries.
"They're over the moon!" the insider said of Kardashian and West. "Kanye always wanted a girl."
The baby is expected to be born in July, UsMagazine.com reported.