To understand SIDS, you need to know that it is NOT a disease or a condition. Rather, SIDS is a diagnosis thats made when an infant dies suddenly and an exact cause CANNOT be found. Most SIDS deaths transpire during the first year of a babys life, with 90% of cases occurring BEFORE the sixth month. The peak age is 2-4 months, and there is a male preponderance, as well as higher occurrence in winter.