Czech Karolina Muchova overcame illness to reach her second consecutive US Open semi-final with a 6-1 6-4 win over Beatriz Haddad Maia.

Muchova left the court after wrapping up the first set with ease, ran off court at 2-1 and again at 3-2 in the second and was seen by the doctor and physio at 4-3.

The unseeded 28-year-old, who only returned to action in June after having wrist surgery in February, will face either top seed Iga Swiatek or American sixth seed Jessica Pegula for a place in Saturday's final.

"It was a weird match," said Muchova. "I had some problems I don't want to comment on but I had to keep running to the bathroom and back.

"Sorry if it disturbed anyone but I had no other choice."

Haddad Maia also had problems and seemed to be in tears before receiving treatment from the doctor at 5-3 down in the second set.