Meanwhile, in the men's singles, Parupalli Kashyap beat Rajiv Ouseph of England 21-15 21-18 to enter the second round of the competition.
It was a hard-fought contest for Saina, who had to stretch herself for a 12-21 21-10 21-12 win over Karin Schnaase of Germany in a match that lasted 49 minutes, while Sindhu took only 39 minutes to get the better of Hong Kong's Pui Yin Yip 21-13 22-20 at the Odense Sports Park here.
Saina will next take on winner of the match between Li Han and Minatsu Mitani.
In another women's singles match, Sindhu was at her dominating best in the first game as she did not allow the Hong Kong shuttler to settle down.
In the second game, Yin Yip fought back and it was a neck and neck battle throughout. But in the end, the world no. 10 Indian held on to her nerves to prevail over her rival.
Kashyap had an easy outing against his English opponent. After beating him comfortably in the opening round, he faced some competition from Rajiv, but the Indian had the last laugh.
Earlier, Ashwini Ponnappa, who paired up with Russia's Vladimir Ivanov in the mixed doubles event, was knocked out of the tournament after a 18-21 18-21 defeat in 30 minutes to Hong Kong pair Yun Lung Chan and Ying Suet Tse.
