65427ca9_by___Toddler_Sleep_Consultants__Impact_on_Sleep
[Week] 15-19 Weeks [Name] Events [Description] Baby is learning to recognize cause and effect, and to predict outcomes (i.e. ‘If I drop this toy, it will fall to the ground, and dad will come and pick it up’). [Impact on Sleep] 
Welcome to the 4 month sleep regression! If baby’s sleep was predictable up to this point, it may all fall apart now. Continue to work on building consistent sleep routines; this will help baby learn that certain events mean sleep is coming. You may also want to work on identifying any sleep associations baby may have; that will help with sleep training. There’s also another growth spurt that happens around 4 months.
Baby Sleep Chart | The Baby Sleep Site - Baby / Toddler Sleep Consultants
Impact on Sleep