Currently the world number five, Pettersen has been in good form of late winning an LET event in China in March and finishing 3rd at the recent Kraft Nabisco Championship. She finished 6th in this event last year.
Three players are at 7 under and two behind Miyazato namely Beatriz Recari, Kim Hyo Joo and Seo Hee Kyung while world number two Stacy Keating is one shot further back again.
The group at 5 under and one behind Lewis includes first round leader Ariya Jutanugarn and So Yeo Ryu.
Lydia Ko is the best of the Australasians, the New Zealander in 28th position after consecutive rounds of 71.
Karrie Webb and Julia Boland lead the Australians after a disappointing day for both, Webb 74 and Boland, making her first cut on the LPGA Tour but slipping to a round of 75. The pair shares 37th position while Katherine Hull Kirk, Sarah Jane Smith and Lindsey Wright also made it through to the weekend but are well back.