But what should be a happy occasion for Kardashian comes amid reports in recent days that Thompson has been mingling with another woman.
After the Daily Mail published video of Thompson and a woman getting close at a party, the Shade Room obtained footage of the Cleveland Cavaliers player entering and leaving a New York hotel with a woman.
Just the day before, Kardashian published a romantic photo of her and Thompson on Instagram with the caption, "We are ready whenever you are little mama 🦋"
A source told E!, the network that airs Keeping Up With the Kardashians, that Khloé had wanted to fly from Cleveland to LA to be with her family after the reports broke, but her doctor wouldn't let her fly due to her pregnancy.
"Her entire world has been turned upside down," the source told E! "She cried hysterically all night."
"She will obviously never be able to trust Tristan again or look at him the same way," the source said. "Her world is shattered. She is in complete disbelief that this is happening."
However, a source familiar with the matter confirmed to BuzzFeed News that Thompson was present for the birth of their daughter.
Kardashian began dating Thompson in late 2016, with the reality star confirming the relationship during an appearance on Jimmy Kimmel Live in November of that same year.
BuzzFeed News confirmed Kardashian was pregnant via an independent source last September, and the youngest Kardashian daughter then publicly announced the news herself on Instagram in December.
Newborn Chicago West is Kim's third child with rapper Kanye West, and Stormi Webster is Kylie Jenner's first child with rapper Travis Scott.