The 27-year-old star, who already has three-year-old son King Cairo with ex-boyfriend Tyga, announced last week she and fiance Rob Kardashian are expecting a baby together.
In an Instagram post, Rob wrote, "Chyna really wasn't feeling well last night, which fell over to this morning."
And Chyna apologised for missing the events and promised to reschedule.
In a message which she has also deleted, she wrote: "Sorry LA & Atlantic City. I really wasn't feeling well LAST night which fell over to this MORNING causing us to miss our flight..