title: Letter: Seasonal variation in incidence of ventricular septal defect.
mesh_terms: D005260:Female; D006345:Heart Septal Defects, Ventricular / Q000453:epidemiology* / Q000401:mortality; D006801:Humans; D007223:Infant; D008297:Male; D009864:Ontario; D012621:Seasons; D012744:Sex Ratio