A crucial and very overlooked factor in your baby's sleep habits is temperament. Temperament determines how predictable and adaptable your baby is, how intensely they feel and react to their emotions, and how much support they need to settle.
Temperament is largely genetically determined although environmental factors also play a part. A very well known study has identified three major temperamental groups: easy going, high needs/sensitive/difficult, and slow-to-warm.
Roughly 40% of babies have the easy temperament, 10% difficult, and 15% slow to warm temperament. 30% of children do not fall into any of the three identified types.
If you have an easy going baby, then you are likely to find that they settle into fairly regular routines with ease, adapt fairly easily to separate sleep, and "self settle" from very young (this just means that they tend to be less disturbed by environmental or emotional change, so don't signal for parental assistance so frequently at night).
If you have a baby with a difficult temperament, then they will likely be very irregular in their routines, need much more closeness, and signal to you often at night.
Slow-to-warm babies need to take things at their own pace and may take a long time to adapt to changes. Introducing changes in sleep will be a very different process with these babies than it might be with easy babies.
As temperament is largely genetically determined, there is nothing you can do about it as a parent except get to know and understand your child, and adapt your parenting to suit their needs. Working with your child's temperament, not struggling against it, will make much happier times for all.
There's a frustrating pattern in which many of the behaviours parents take up in order to meet the needs of their sensitive babies get blamed for baby's regular wakings. For example, parents of sensitive babies are more likely to bed-share and respond quickly at night, because of the speed and intensity with which sensitive babies escalate their reactions. They are then made to feel responsible for their baby's frequent waking.
But it's real chicken and egg stuff - bed sharing babies *may* wake more often, but that's likely because they are more likely to be sensitive, and parents begin bed sharing to make things easier for everyone.
When you are thinking about your baby's sleep, and particularly when you are thinking about making changes, it is crucial to understand your baby's temperament so that you can work on changes in ways that are most likely to be successful. I've said it before and I'll say it again: there really are no one-size-fits-all solutions when it comes to infant sleep.
Where do you think your baby falls in the temperament spectrum? Can you see how it might impact their sleep and the choices you make around it as a parent?