What is a sleep nest and do you really need it? There are a few great options on the market now, most notably the DockATot (aka Sleepyhead in some markets) and the Cocoonababy - which one should you choose?
A sleep nest is a sleeping aid that aims to mimic the comfort and positioning that your baby experienced while in the womb, to help him or her sleep longer and prevent the startle (moro) reflex from waking them. While it's not intended to be a co-sleeper, some parents do use it to co-sleep with the baby more safely than without. They can also be used as a comfy lounger or play mat with a play gym with stimulating shapes and colors over top.
You've probably seen the raving reviews that babies have sometimes slept through the night simply by introducing a baby nest, and it very well could be true, because babies wake periodically (we all do) and when they are sufficiently comfortable they will simply slip into their next sleep cycle. Because the surface is soft, it also prevents flat head from developing.
Ultimately, the preference is very personal for you and your baby, but here are some similarities and differences to help you decide!
The Cocoonababy helps baby lie in a semi-fetal position on their backs, which both trains them to sleep comfortably on their backs and feel the familiar position of being in your womb at the same time. It comes with a belt to keep your baby from moving and falling (though it doesn't replace the need to supervise them in one!) and you can also buy an optional Cocoonacover during the winter or if your baby is sleeping in an air-conditioned room. It's more compact but cannot be folded, and still suitable to bring with you while traveling with baby.
The DockATot allows your baby to lie more freely on a flat surface and roll if they wish, so when they are newborns you may still need to swaddle them for that same "in-womb" feeling. Your baby may have a preference to sleep on their side or roll, which is less safe before they have the strength to lift their neck and head, and could lead to flat head on one side or the other if there is a strong preference. The DockATot Grand for toddlers is also a great option for helping to transition to a big cot, when the sudden increase in surrounding space can be a little unsettling.
Both the DockATot Deluxe and Cocoonababy can be used from newborn to about the same age, when they need to be transitioned to a bigger sleep space. Prices are similar and both have excellent resale value. They both come with a carrying case and can be taken with you on family travel.
Good night, sleep tight!