The 3-4-5 month sleep regression is a period when your baby's sleep patterns change and causes baby to wake frequently at night and take short naps. Sleep regressions are exhausting but you can help your baby sleep better! Learn 20 tips based on my 10+ years as a sleep consultant to get through this frustrating and exhausting period. What is The 4 Month Sleep Regression? The 4 month sleep regression means your baby is likely waking up excessively in the middle of the night and/or taking