This book changed my life!! New mommies, please get this book. You can start sleep training starting at 8-12wks. I started right at 12wks (3wks before I went back to work) and I'm so happy. If you're a nursing mom, you will have to pump and bottle feed in order for the training to work. If you're like me, and don't really care to pump, at least try it out for a week. It took Baby 4 days! To sleep through the night after only sleeping for 2-3hrs at a time!