Wie, at 4-under 136, holds a three-shot lead on Lexi Thompson, who made a late-day charge to 1-under after matching Wie's 68.
Wie is halfway to winning her first major. The 24-year-old has seven top-10 finishes in tournaments this year.
Wie's latest 68 came without much drama as she put together a steady round. Starting on the 10th hole, she didn't have a bogey until reaching the par-4 first hole and she closed the round with back-to-back birdies.
Her 15-foot putt for par on the second hole and a 24-footer on the sixth hole allowed her to escape trouble.
Thompson wrapped up her second round on the front side and it was a good stretch. She had birdies on three consecutive holes (Nos. 3-5).
Wie completed her round before afternoon rains. Only three golfers who began in the morning recorded a score under par, with Yang and Scotland's Catriona Matthew joining Wie. Yang and Matthew had 69s.
Lewis, who had the only bogey-free round in the entire tournament Thursday, started with a bogey on the first hole. She had an erratic opening stretch, with only two pars across her first eight holes while playing the front nine in 2-over.
Lewis pulled it together later, playing the last five holes in 1-under.Copyright © 2015, The Baltimore Sun