Serena Williams began her bid to make history at the US Open in bizarre fashion as her opponent Vitalia Diatchenko retired after 30 minutes.
The world number one dropped just five points against a clearly injured opponent at Flushing Meadows.
Williams, 33, is hoping to complete the first tennis calendar Grand Slam in 27 years.
Men’s top seed Novak Djokovic made swift progress, but fourth seed Kei Nishikori was beaten.
The Japanese player, last year’s runner-up, went down 6-4 3-6 4-6 7-6 (8-6) 6-4 to Frenchman Benoit Paire.
“It’s always very sad to lose in the first round, but I think he was playing good tennis so I don’t think I played bad,” said Nishikori.
Djokovic swept past Brazil’s Joao Souza 6-1 6-1 6-1 to reach round two, but there were a host of upsets in the women’s draw.
Ivanovic, the seventh seed, was beaten 6-3 3-6 6-3 by Dominika Ciblukova of Slovakia, and she was followed out of the tournament by five more seeds.
Source: bbc sport