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Fourth Trimester Theory

The Fourth Trimester Theory proposes that human babies are born earlier than they should be, compared to other mammals. This is basically because their heads would grow too big for safe delivery if they stayed in the womb for much longer, so they are born before they are really ready. It means that they are, in essence, still more like a fetus than a baby when they are born.

If we compare human babies to other mammals, who are able to walk just a few hours after birth, we can see that our babies are born in a much higher state of helplessness and dependence.

In terms of sleep, this means that we need to try to recreate womb like conditions as much as possible. Otherwise, the baby will be distressed and may cry and fuss much more, or even suffer from colic type symptoms. Additionally, the baby may be having difficulty adjusting to being outside the womb. The fourth trimester theory can help us as parents to understand what they are going through.

Read more detail here about the Fourth Trimester Theory, or here, or the ‘second nice months’ here.

So what can we do?  Dr Harvey Karp suggests ‘5 S’s’, (five things beginning with S), as a way to soothe the baby.  These things will help recreate a womb environment.  As described on his website:

Swaddling: Tight swaddling provides the continuous touching and support your baby is used to experiencing within the womb. (Please check here for safe swaddling techniques, make sure the room is not too warm, and do not swaddle a baby over three months who has not been swaddled before).

Side/stomach position: The infant is placed on their left side to assist in digestion, or on their stomach to provide reassuring support. “But never use the stomach position for putting your baby to sleep,” cautions Karp. Sudden Infant Death Syndrome (SIDS) is linked to stomach-down sleep positions. When a baby is in a stomach down position do not leave them even for a moment.

Shushing sounds: These imitate the continual whooshing sound made by the blood flowing through arteries near the womb. (This can be created by a white noise app, YouTube womb noises or heartbeat, or other similar device. Be careful though, as many white noise machines and apps play a sound that is too hard and hissy – it should be quite low pitched. Dr Karp asked us to remind you that The Happiest Baby CD has sounds that are specially engineered to be more effective in calming crying and imitating the womb, to help babies sleep sweetly).

Swinging: Newborns are used to the swinging motions within their mother’s womb, so entering the gravity driven world of the outside is like a sailor adapting to land after nine months at sea. “It’s disorienting and unnatural,” says Karp. Rocking, car rides, and other swinging movements all can help. (Babywearing, when done safely, is a great way to recreate the swinging motion of the womb).

Sucking: “Sucking has its effects deep within the nervous system,” notes Karp, “and triggers the calming reflex and releases natural chemicals within the brain.” (Sucking can be on a breast or pacifier.)

Recreating a womb environment can help your baby sleep, as the baby will feel more rested and secure. It will reduce the shock of transitioning from inside the mother’s body to the outside world.  These techniques are really worth a try.

Dr Karp also says it’s important to mention that men do the 5 S’s great, and are often the best swaddlers in the family.

Read more about the Fourth Trimester Theory or Dr Harvey Karp‘s work here.

Dr Harvey Karp has published several books, CDs and DVDs.

He asked us to add this comment regarding his books and DVDS: “Dr. Karp’s book on sleep (The Happiest Baby Guide to Great Sleep: Birth to Five Years) has several gentle ways to prevent or resolve sleep problems from birth to five years.  The 5 S’s don’t just feel good, they also activate a reflex – a calming reflex – which can quickly calm a baby. However, like any reflex, it must be done correctly. That is why we made The Happiest Baby DVD, to help parents learn exactly how to do the correct techniques.”

Parent Reviews: One dad told us “We found out about these techniques before Jamie was born and they work like magic. I was surprised how loud the shushing sound had to be – I mean it’s really really loud. But they really work. Definitely worth finding out about these. I tell anyone I know who’s going to have kids.”

Acknowledgement: We thank Dr Harvey Karp for his generous time in helping us make sure this page is an accurate representation of his work. We hope you will find it helpful, and hope it will help to introduce more readers to him.