Babies are not designed to sleep ‘through the night’ Now I know what you’re thinking: You’re saying, “She’s rationalizing. She’s making excuses.” I can hear you saying, “She’s wrong.” And that’s because I’ve heard it all. Of infants who began sleeping through the night by their 16th week or, in some cases, their 12th. Further, a 2018 study showed that 57 percent of 6-month-olds were not “sleeping through the night” for 8 hours. Even toddlers who wake early or in the middle of the night are developmentally normal.