Hoping to “crack the code” about how to best attract and retain women lawyers, Orrick, Herrington & Sutcliffe is rolling out what its leaders say is among the most generous parental leave programs at any major U.S. firm.

The program, which is available to all lawyers, including partners, and to both men and women, increases paid parental leave from 18 weeks to 22 weeks. Primary caregivers can take up to nine months’ unpaid leave, up from seven months. In addition, the firm is also strengthening its flexible work program, which allows lawyers working at least 60 percent of full time to continue to advance and receive proportionate pay. Some 40 women attorneys, or 17 percent of those at the firm, used flexible work arrangements last year, according to Orrick.