z codes that can only be used as primary diagnosis?
['Z33.2 Encounter for elective termination of pregnancy.', 'Z31.81 Encounter for male factor infertility in female patient.', 'Z31.83 Encounter for assisted reproductive fertility procedure cycle.', 'Z31.84 Encounter for fertility preservation procedure.', 'Z51.0 Encounter for antineoplastic radiation therapy.']