@MsFrog
I posted at the end of my tether the other night asking for advice, so I am glad to have had some! But I am confused about it being inherently "unhealthy" to cuddle him and put him down if he then sleeps (assuming the waking after 30mins thing has stopped, it's only been 2 nights!) - is it likely to cause problems later on?
FATEdestiny- you seem to have done a lot of research in to baby sleep
It's my day job. I'm a baby sleep consultant.
OK - The unhealthy sleep habit comes specifically from being got to sleep one way, and waking elsewhere. So there is nothing (zero, nada, zilch) "unhealthy" about cuddling baby to sleep.
The healthy way to approach that would be to properly embrace cosleeping. So baby goes to sleep cuddling you, moves around in the night cuddling you, wakes cuddling you. All good.
Now for the more detailed explanation I need to back up a bit....
Babies in the womb sleep passively. By that I mean as long as all needs are met, baby will be asleep. There are no sleep cycles. This continues through the "Fouth Trimester", the first 3-4 months of life when sleep is very womb like and passive.
Past about 4 months, sleep irreversibly progresses. It changes to be a more active endeavour with cycles of deep sleep and light sleep. Sleep is no longer passive, it takes active effort to get baby to sleep. (This is sometimes called the 4 month sleep regression).
Why do humans sleep in cycles and not just have continuous sleep? The answer is evolutionary, it's a left over from cavemen times. Mammals are at risk to preditors, even when sleeping. To keep themselves safe we developed cycles of sleep which include an "environment check". This is a largely unconscious, but partially semi-concious period check throughout our sleep to ensure we continue to be safe.
This is why humans sleep in cycles. There will be a period of light sleep when its/easy to be woken, a period of deep sleep when vulnerable to dangers, and interspersed, brief environment checks between cycles.
In modern day adults this environment check may take the form of rolling over, pulling the duvet up/down, changing positions. Semi-concious few seconds that you don't actually wake up for and barely notice.
Now imagine you want to bed as normal and at 2am you want to roll over and suddenly realised you were no longer in bed, you're now in the back seat of a car. You wouldn't just roll over and go back to sleep. You'd be immediately sat up, disoriented, thinking WTF!?, and be wide awake pretty damn fast. That's the whole purpose of the environment check, it's what it's for. Most of the time you roll over and think nothing of this pause in sleep. But when it's needed, you wake up FAST.
From 4 months onwards, baby is learning to deal with these changes in sleep. From passive sleep to active sleep and learning to deal with sleep cycles, light sleep phase and environment checks - all of this is new.
As baby gets older, if baby is triggered to wake more fully than is necessary regularly between sleep cycles, it's going to be harder for them to learn to link consecutive cycles and in the mean time sleep will be more disruptive than it needs to be.
You child will, ultimately learn to go to sleep where they stay asleep. It's a necessary skill for an older child to learn (be it preschool, school age, teenager, adult). Now that might always be going to sleep with mum in mum's bed. That's ok, nothing wrong in that. But it will not be helpful for, say, a 10yo/15yo/5yo/3yo (whatever) to be falling asleep on the sofa in front of the TV every night and being carried to bed already asleep. That is not a healthy sleep habit. That child would have an unhealthy sleep habit, that will disturb their normal natural bodily sleep cycles.