Lydia Ko has had an up and down opening round but is well in the hunt for a third straight major championship title in women's golf.

The world number one carded an even par 71 at the women's PGA Championship in Washington State.

Ko had two birdies and two bogeys to be twos shots off the pace set by Norway's Suzann Pettersen, American Christina Kim and In-Kyung Kim of South Korea.