International Society of Andrology and International Union of Pure and Applied Chemistry, Chemistry and Human Health Division, Clinical Chemistry Section, Commission on Nomenclature, Properties And Units (C-NPU) and International Federation of Clinical Chemistry Scientific Division, Committee on Nomenclature, Properties And Units (C-NPU)2: Properties and units in the clinical laboratory sciences XIII. Properties and units in reproduction and fertility (IUPAC–IFCC technical report 1997)