Khloe posted a shot of her belly with her and Tristan Thompson's hands wrapped around it. She says, "I know we've been keeping this quiet but we wanted to enjoy this between our family and close friends as long as we could privately."

We broke the news back in September that she and Tristan were expecting their first child together.

As for those bands on Khloe's left ring finger -- don't get too excited.

She wears 'em all the time -- has been for more than a year now. Despite some reports Tristan and Khloe secretly got married ... we're told no dice! They're not husband and wife yet.

Baby steps, people.