Sleep regression. It's a phrase you probably didn't know existed before you had a baby, but now? Now that your baby is waking every 20 minutes, and you are exhausted beyond all reason? Now that your toddler is waging a fierce anti-nap campaign? Yeah - it's a phrase you're probably familiar with! Sleep Regressions: What They Are A sleep regression describes a period of time (anywhere from 1 - 4 weeks) when a baby or toddler who has been sleeping well suddenly starts waking at night,