title: VA to study twins.
mesh_terms: D003130:Combat Disorders / Q000453:epidemiology; D005260:Female; D006801:Humans; D008297:Male; D008887:Military Medicine; D011247:Pregnancy; D014427:Twins; D014481:United States; D014493:United States Department of Veterans Affairs; D014728:Veterans; D014744:Vietnam; D014857:Warfare