29 C.F.R. § 1604.7

Pre-employment inquiries as to sex.

        A pre-employment inquiry may ask “Male........., Female.........”; or “Mr. Mrs. Miss,” provided that the inquiry is made in good faith for a nondiscriminatory purpose. Any pre-employment inquiry in connection with prospective employment which expresses directly or indirectly any limitation, specification, or discrimination as to sex shall be unlawful unless based upon a bona fide occupational qualification.

Official source