Kardashian first learned the news herself from sister Kylie Jenner, who for some reason was determined to be the first to know her sister's baby's sex. Jenner is also a new mom after giving birth a month ago to her first child, daughter Stormi.
"Kylie was like, 'I want to be the first phone call!'" Kardashian told her doctor in last week's episode. "And I was like, 'Why?' I want to know why she wants to know so badly." The doctor then clarified by asking Khloé: "Oh, for me to call her? If you give me permission, I can."
Prior to the big reveal in Sunday's finale, Khloé was "pretty much convinced" that she was having a boy, she said in a confessional.
"I kind of am too," sister Kim Kardashian agreed.
"I have such anxiety and nerves to find out what I'm having, but I just need Kylie to f—ing call me," Khloé admitted.
The good news came in the form of a phone call from Jenner while Khloé was on vacation with sisters Kim and Kourtney Kardashian to San Francisco.
"I'm dying to know the gender of my baby," Khloé told her little sister.
"Okay, are you sitting?" she responded.
"Kylie! Just say it!" Khloé shouted.
"You're having a girl!" she said.
"You're lying," Khloé responded.
"I don't feel like I'm having a girl," Khloé said, adding she was "in a state of shock."
"When you have your mind made up as to what you're having ... and then when you find out it's the complete opposite, it's just a bit of a shock," she says in a confessional.
Moments later, when Khloé told Kourtney, the mother-of-three said she was "shocked" by the news.
The E! family also marked the occasion with a speciality cake, Khloé revealed on Instagram at the start of the episode.
"How cute is Kylie for getting me this cake?!?! Tune in to tonight‘s episode to find out what’s inside!" she captioned the photo of the ornate cake, white with flowers and "Congratulations, it's a..." written on the top.
Photo credit: Instagram/@khloekardashian