From the magazine "Baby Talk" (May 2009), which is quoting Steven Shelov, MD, editor-in-chief of the American Academy of Pediatrics' book "Caring for Your baby and Young Child".
"Unless you use well water, you don't have to sterilize bottles and pacifiers. Ever. Not before their first use. Not even for premies. 'It's an outdated practice held over from when we didn't have safe water supplies in this country (USA).'
You still have to clean the dishwasher or by hand...before every use, including the first. Bacteria can grow in liquid left at the bottom of bottles.
Go BPA-free.
Wash your hands. The biggest threats to the purity of bottles are your germy fingers. That's why, in neonatal intensive care units they don't sterilize,but they do scrub up often."