If the original/source text is this one:

The U.S. Department of Agriculture (USDA) prohibits discrimination
in all its programs and activities on the basis of race, color,
national origin, age, disability, and where applicable, sex, marital
status, familial status, parental status, religion, sexual orientation,
genetic information, political beliefs, reprisal, or because all or part
of an individual’s income is derived from any public assistance
program. (Not all prohibited bases apply to all programs.) Persons
with disabilities who require alternative means for communication
of program information (Braille, large print, audiotape, etc.)
should contact USDA’s TARGET Center at (202) 720–2600 (voice
and TDD). To file a complaint of discrimination, write to USDA,
Director, Office of Civil Rights, 1400 Independence Avenue, S.W. ,
Washington , D.C. 20250–9410 , or call (800) 795–3272 (voice) or
(202) 720–6382 (TDD). USDA is an equal opportunity provider and
employer.

Taken from:

http://www.aphis.usda.gov/publications/biotechnology/content...

I believe that "estado paternal/maternal" is the correct option.

Another example:

(...) sin distinción de raza, religión, color de piel, sexo, edad, origen nacional o descendencia, estado matrimonial, estado paternal o maternal, orientación sexual, discapacidad o estado como veterano militar (...)

Taken from: http://www.ces.purdue.edu/hancock/

And:
... national origin, sexual orientation, marital or parental status, age, or ancestry. ... orientación sexual, estado civil o paternal, edad, o ascendencia. ...

From: http://www.nebraskaadvocacyservices.org/what_we_do/index.htm...


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Note added at 6 days (2009-01-19 16:41:01 GMT) Post-grading
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Un placer! Gracias! :)