I get this question all the time – you may have heard of the dreaded “4 month sleep regression”, where any decent sleep your baby’s been having goes completely out the window. I put it in quotes because a) it doesn’t happen at 4 months – it can and often does start as early as 12 weeks! And 2) it’s not exactly a regression.
What happens is two things – first, some brain development changes around the 3-4 month mark mean their sleep cycles become more distinct and more like adults’, light followed by deep etc. So they wake at the transition between cycles and the second thing happens – they’re more engaged, interested, and active, so they want to see you. They rouse a little and think, “Hey, my parents are cool, I want to see them!” and the parents, who’ve up til this point had a baby who did a 6-10 hour stretch overnight, are like “Oh, the baby’s awake! Is something wrong? Are you hungry? Hi Sweetie! <all smiles>” and they pick up, change, even feed the baby, who LOVES this. “Party with Mom/Dad at 3 am? Don’t mind if I do!” This is where it becomes a REGRESSION, because we re-introduce new habits that we previously lived without, eg multiple feeds a night. This can continue for MONTHS, even though Baby is more than capable of sleeping through the night, because parents just don’t know what it means or how to fix it.
BUT, if you understand this period, and your baby has the skills to put themselves to sleep at bedtime and during the night (ie, is sleep trained), this period just cruises by without even much notice, because if you hear the baby rouse during the night (usually just with some movement and chatty noises), you know they’ll resettle themselves quickly and you don’t create new issues.
A baby who is NOT sleep trained, and needs to be put down fully asleep, wakes during the sleep cycle cross confused and concerned that the cozy arms they fell asleep in are gone – just like if you fell asleep in your bed and woke up in the bathtub.
Giving your baby the gift of the skill of putting themselves to sleep is an amazing thing, not just for you but also for THEM. Take away that nightly anxiety of waking up in a strange place that’s not where they fell asleep, give them the security of knowing that they’ll wake up exactly where they fell asleep and feel safe enough to resettle peacefully instead of screaming for you to come in and re-create the conditions they need to fall asleep.