"This Mother's Day will be the most special yet!" she said. "I still can't believe I'm a mom -- it feels like such an honor. Now it feels even more important to honor all the amazing women in my family!"
Kardashian gave birth to True on April 12 following reports Thompson cheated during her pregnancy.
The pair have yet to address their relationship status, although Kardashian's sister Kim Kardashian commented on the situation Monday.
"I don't even know how to describe it other than it's just so [expletive] up," Kim said on "The Ellen DeGeneres Show."
"We really were rooting for Khloe and we still are," she added.
"She's so strong and she's doing the best she can. It's a really sad situation all over. I kind of made this rule ... if there's a baby involved, I'm going to keep it cute, keep it classy and try not to say anything negative because one day True's going to see this."
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Kim said Khloe is focused on True and not her relationship with Thompson.
"I think she's not thinking of anything," the star shared. "I think she just wants a clear head and just wants to be alone with her baby and figure that out."
Kim herself is parent to 4-year-old daughter North, 2-year-old son Saint and 3-month-old daughter Chicago with husband Kanye West.
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