Sleep regressions occur at many ages usually around 6 weeks, 4 months, 8 to 9 months, 15 months, 18 months, and 2 years old. It's a phrase you probably didn't know existed before you had a baby, but now? Now that your baby is waking frequently, and you are exhausted beyond all reason? Now that your toddler is waging a fierce anti-nap campaign? Yeah - "sleep regression" is a phrase you're probably familiar with! Sleep Regressions: What They Are A sleep regression describes a period of time