Policy Memorandum: Adjudication of Immigration Benefits for Transgender Individuals; Addition of Adjudicator's Field Manual (AFM) Subchapter 10.22 and Revisions to AFM Subchapter 21.3 (AFM Update AD12-02) [open pdf - 313KB]
"This Policy Memorandum (PM) and accompanying revisions to the AFM [Adjudicator's Field Manual] articulate USCIS [United States Citizenship and Immigration Services] policy regarding assigning appropriate gender designations on documents issued to transgender individuals and the adjudication of benefits applications involving the marriage of transgender individuals."
Policy Memorandum: PM-602-0061
U.S. Citizenship and Immigration Services: http://www.uscis.gov/