Found this tidbit on the Salus site. It is a letter from Transport Canada stating that since there is no standard for PFD's for infants under 20 lbs, they are not required to wear one. Salus does make one they claim to have tested successfully but TC doesn't approve them. I'd put one on a baby anyway whether approved or not.....:
http://www.salusmarine.com/wp-content/uploads/2014/06/Bijoux-Baby-Vest-Letter-from-TC.jpg
http://www.salusmarine.com/?products=bijoux-baby-vest