Bertens, one of the favourites for the title, was 3-1 behind in the first set when she called for the doctor, saying she had no energy and felt shaky.

The Dutchwoman won the Madrid Open on 11 May, beating 2018 French Open champion Simona Halep in the final.

Kuzmova will play either Britain's Johanna Konta or Lauren Davis of the United States in the third round.

"Yesterday I felt good. No problems at all. I was practising, resting, and I felt really well - ready for today," said Bertens.

"This morning I woke up at 3am and felt really sick. Vomiting, diarrhoea all night long, all day long. I felt a little bit better before the match.

"I had some sleep and I wanted to give it a try but then, as soon as I started warming up right before the match, it started again.

"There was not any energy left. I just wanted to give myself the chance to play and see what's happening. But it was better maybe not to step on the court today."

Earlier, world number two Karolina Pliskova continued her bid for a first Grand Slam with a routine win over Kristina Kucova.

The big-serving Czech won 6-2 6-2 against the world number 203 in just 56 minutes.

Karolina Pliskova's best Grand Slam performance came in 2017 when she was runner-up at the US Open

Pliskova hit 25 winners and six aces as she maintained the strong clay-court form that saw her win the Italian Open in the run-up to Roland Garros.

Sloane Stephens and Garbine Muguruza also both progressed to the third round with straight-set wins.

American seventh seed Stephens, last year's runner-up, beat Spanish world number 75 Sara Sorribes Tormo 6-1 7-6 (7-3).

Muguruza, the 2016 French Open champion, won 6-4 6-1 against 172-ranked Johanna Larsson of Sweden.

The Spaniard will play ninth seed Elina Svitolina in the third round after the Ukrainian received a walkover when compatriot Kateryna Kozlova pulled out.

Pliskova meets Petra Martic while Stephens plays Polona Hercog.

Elsewhere, 22nd seed Bianca Andreescu of Canada pulled out for her second-round match with American Sofia Kenin, scheduled for Thursday, because of injury.

Kenin will meet the winner of Thursday's second-round match between Serena Williams and Kurumi Nara.