Martina Eberl of Germany birdied six of the last seven holes for a 66, taking a one-shot lead in the 54-hole tournament. Melissa Reid of England (67) birdied three of the last four holes.
Sorenstam, who will retire at the end of the season, shot par through 14 holes before she birdied the next two.
Im not satisfied and it could have been better, Sorenstam said. I did what I could today but I didnt really get it together. I should have taken more advantage of two of the par 5s.
A winner of 10 majors and 72 LPGA titles, the 37-year-old Sorenstam plans to get married, start a family and focus on business and golf interests.
Nikki Garrett of Australia eagled the 18th for a 68 and shared third with Denise-Charlotte Becker of Germany. Laura Davies of England shot 73.
Eberl recently won the Italian Open for her first victory in six years on the Ladies European Tour.