title: Possible changes in male fertility over a 15-year period.
mesh_terms: D006801:Humans; D007248:Infertility, Male / Q000453:epidemiology* / Q000473:pathology / Q000503:physiopathology; D008297:Male; D009845:Oligospermia / Q000453:epidemiology; D044469:Racial Groups; D013019:South Africa; D013076:Sperm Count; D013081:Sperm Motility; D013094:Spermatozoa / Q000473:pathology