Labor Unions: Organizations comprising wage and salary workers in health-related fields for the purpose of improving their status and conditions. The concept includes labor union activities toward providing health services to members.Labor, Obstetric: The repetitive uterine contraction during childbirth which is associated with the progressive dilation of the uterine cervix (CERVIX UTERI). Successful labor results in the expulsion of the FETUS and PLACENTA. Obstetric labor can be spontaneous or induced (LABOR, INDUCED).Labor, Induced: Artificially induced UTERINE CONTRACTION. Generally, LABOR, OBSTETRIC is induced with the intent to cause delivery of the fetus and termination of pregnancy.