Babies, like adults, can just have “off” nights when it comes to sleeping. Maybe their tummy is upset or there is a noise that keeps waking them. These nights are not considered regressions, especially if they only occur a night here and a night there. Sleep regressions are prolonged and last from 2-4 weeks. Here are signs of a

sleep regression: Baby sleeping blanket

Crying when put down to bed
Trouble falling asleep
Frequent waking throughout the night
Short naps
Increased fussiness