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A Guide To The 'Fourth Trimester'

Your baby doesn’t want to be put down, cries for you constantly, feeds very often, and you’re not sure what to do, or what on earth is going on. This behaviour is explained by the theory of the ‘fourth trimester’.

We see so many new mummies asking the very same questions in our online community, so we decided to put together a guide to help reassure and advise any parent who isn’t sure if this behaviour is normal, or needs specific action. You may be asking questions like;

  • What is the fourth trimester?
  • Why do babies go through the fourth trimester?
  • How can we help our baby through the fourth trimester?
  • Which books can I read on the fourth trimester?

Don’t worry, we’ve got you covered, mummies & daddies! We will take a look at each question as we go forth.

We’ll start off by looking at the question; “what is the fourth trimester”?

Pregnancy itself consists of three trimesters, right? Think of the fourth trimester as the newborn period. How long it lasts will vary, but the average duration is considered to be around three months. The fourth trimester encompasses a period of huge changes and developmental leaps for your baby!

The NHS states that; “By the end of pregnancy most women and partners are aware of the 3 trimesters of pregnancy – often simplified to early, middle and late pregnancy, times you are careful to help your baby stay safe and comforted so they can develop into healthy term babies. However, most parents do not think of the first 3 months with a newborn baby in the same respect.”

It’s easy to forget that they’ve just come from nine months of being constantly held in your warm, snug womb, with your heartbeat comforting them and no hunger, and are now in the big wide world with an empty belly and open space, so it’s understandable that it’s a daunting time for the little mites and they will need your physical comfort to reassure them as they find their place in their brand new world. There are also scientifically proven benefits of merely holding and cuddling your baby, so it is actually no longer medically advised to ‘leave them to cry’ these days. It doesn’t spoil a child to nurture them.

You may find that the washing up gets left a while longer, the ironing might go undone for a while, but you know what? It’s such a vulnerable, intimate time for you and your baby – enjoy the cuddles.

Why do babies go through the stage of the ‘fourth trimester’?

As we discussed above, it’s a vital developmental period for your tiny tot, on top of adjusting to their new environment. Rapid physical growth, huge brain development, increased sense development – it’s all rapid, and it’s a lot for such a small person to endure! Picture your baby’s brain like a sponge – during the fourth trimester, this sponge soaks up a lot more during the fourth trimester when compared to other developmental stages due to how much growth of neural pathways that occurs.

How can I help my baby through the fourth trimester?

Fundamentally, the best thing you can do for your baby during the fourth trimester is to cuddle and hold them. Anyone telling you that you’ll make a rod for your own back’ is giving you outdated and debunked guidance, so follow your instincts and relish your baby.

We love this guide on ‘The 5 S’s’ by Happiest Baby. I found it really handy, and it’s simple, easy to follow advice that doesn’t over complicate matters. These 5 steps trigger what is known as ‘the calming reflex‘, which Happiest Baby also describes well here.

  • Swaddle – this keeps baby snug, much like your womb.
  • Side or stomach (in your arms that is – don’t put a newborn to sleep on their stomach!) – this is a great position to calm fussiness. The ‘tiger hold’ is a popular hold that goes along these lines.
  • Shush – white noise mimics the noise your baby was soothed by in your womb.
  • Swing – your baby was rocked to sleep by your movements during the first three trimesters, so a swing is a natural choice for soothing a baby during the fourth trimester, at least when you need to nip to the loo or grab some food!
  • Suck – how you go about this is your choice. You may wish to avoid a dummy, especially if breastfeeding. You may also find that this ‘S’ applies to you if your baby enjoys comfort nursing!

Product Recommendations To Help During The Fourth Trimester

With the 5 S’s above in mind, we knew these three products would be perfect!

  • The Gro Company products are safe sleep approved by The Lullaby Trust, which is always reassuring as they’re a leading voice when it comes to safe infant sleep. Find their 2 pack of swaddles* here.
  • Ewan the Dream Sheep* is a white noise plush, and our mummies RAVE about him – just keep him out of the cot as The Lullaby Trust advise a safe cot is an empty cot.
  • One of the most highly recommended swings amongst our parenting community is the Ingenuity Swing-2-Seat* as it lasts through different stages of your little one’s growth and is super comforting.

Are there any good books about the fourth trimester?

There are LOADS of amazing reads by experts in the field on the topic of the fourth trimester. These are the top four we’ve spotted recommended in our parenting community by real mummies, and the reviews are very promising too! I personally enjoyed How To Grow a Baby when my little one was a newborn, it really helped to clarify so many things for me and my husband. The Fourth Trimester by Kimberly Ann Johnson is a particularly good read too as it also focuses on you as a new mummy – it’s too easy to forget to look after ourselves when baby arrives!

Find How To Grow a Baby by Clemmie Hooper here*.

Find The Fourth Trimester by Kimberly Ann Johnson here*.

Find Your Baby Skin to Skin by Rachel Fitz-Desorgher here*.

Find The Fourth Trimester: Through The First Three Months by Susan Brink here*.


With all these tips and recommendations, it’s also important to remember the following…

  • This behaviour is normal! If your baby seems in pain beyond the realm of normal newborn behaviour, however, please see your GP to check for colic/reflux.
  • You are your baby’s entire world, the most special title anyone could be bestowed. Enjoy it!
  • The tiredness WILL pass, we promise.
  • Disregard anyone who tells you you’re ‘spoiling’ your baby.
  • Don’t worry about the housework. Time for that will come.
  • YOUR health and well being is important too. We know the fourth trimester can be taxing on a tired new parent…

This infographic from Carrying Matters is a really useful way to get to grips with the fourth trimester.

Are there any tips on the fourth trimester that you’d like to share with new mummies? Let us know in the comments!

Love from Katie. Xx

The fourth trimester is the 12 weeks after your baby is born.

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