Unseeded Bulgarian Tsvetana Pironkova has stunned former Wimbledon and French Open champion Garbine Muguruza in the second round of the US Open.

The 32-year-old, who gave birth to a son in April 2018, is playing in her 12th Open but her first tournament since Wimbledon in 2017, prevailed 7-5 6-3 over the Spanish 10th seed.

Pironkova has no world ranking because of her lay-off, but she was a 2010 Wimbledon semi-finalist, and the victory was her 22nd against a top-20 player.

“If you make a good schedule and have the right motivation, you can combine the two things, motherhood and being a professional tennis player,” Pironkova said.

“It takes a lot of work but, you know, everything takes work.”

“It’s just great to be playing without that extra pressure I had on myself before,” she said.

“Before it was almost like a life and death situation for me to win a match. Right now it’s not really like that. It’s enjoyment to be on the court.”

“It’s not something super new,” Pironkova said. “I was moving well and hitting the ball well. Why not win?”

Australian Open champion Sofia Kenin advanced to the third round by beating unseeded Leylah Fernandez 6-4 6-3.

Amanda Anisimova won a match-up of American teenagers, rallying past wild card Katrina Scott 4-6 6-4 6-1.

Sorana Cirstea rallied from a set down to upset ninth-seeded Briton Johanna Konta 2-6 7-6 (7-5) 6-4.

The unseeded Romanian sent down 37 winners and won 13 of 16 points at the net to advance to the third round at Flushing Meadows for the third time in her career.