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The 411 on baby onesies: Everything you need to know



Brought to you by the Kiindred Editors. Our team are committed to researching and writing on all the things we know you will want to know about, at each stage of your pregnancy and parenthood journey.
Created on Oct 22, 2023 · 5 mins read

Onesies are the MVP of your newborn’s wardrobe. Forget all the frills, buttons and don’t even get us started on tulle.

In those early weeks and months with a newborn, onesies are your best friend. You’re all about survival, so do yourself a favour and save the fancy outfits for down the track. There will be plenty of time for that, but what other time in a human’s life is it acceptable, nay, encouraged, to spend all day in a onesie?

For those first few weeks and months, your baby will be sleeping around the clock. And when they’re not sleeping they’re feeding, cuddling or ‘playing’, aka tummy time, or chilling. So, comfort really is key.

We’ve broken down everything you need to know about buying onesies for your little one.


Onesies are the foundation of every good baby wardrobe. They are your go-to every day – simply vary the fabric and style for the weather, and layer accordingly. Opt for thicker fabrics with long sleeves in winter, and then you can add singlets, bodysuits or cardigans as you need.

In the warmer months, you can go for lighter fabrics and short sleeve styles for keeping cool.


It can be so tempting as a parent-to-be with a shopping list of items as long as your arm for your new baby, to opt for cheaper garments. However, the problem with cheaper clothing is that they are typically made from cheap fabrics that are not ideal for your baby’s delicate skin (nor the environment). They often don’t last as long either which means you are spending more money in the long run, replacing them.

When you opt for good quality, 100% organic cotton onesies, you know that you are not only caring for your baby’s skin but you are also buying a product that will stand the test of time. Not only will it last for this baby, but it will also still be as good as new if you have more babies (or to pass on to friends.)

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Buttons and press studs need not apply. We cannot stress this enough. When you are changing countless nappies a day and often in the dark of night, you do not want to be fiddling with buttons or studs. You can 100% guarantee they will NEVER match up. We recommend zips all the way.

Newborn babies don’t have control over their little hands and can often scratch themselves accidentally with their fingernails. So, optional inbuilt mittens are a great way to help your little one stay scratch-free – because we know mittens and socks never stay on. And just like us adults, there the first thing to go missing in any laundry.

Sizing guides

Baby sizing is confusing, so we’ve helped break it down for you.

As a general rule, sizing for babies goes:

  • 0000 = Newborn
  • 000 = 0 – 3 months
  • 00 = 3 – 6 months
  • 0 = 6 – 12 months

Age is a great starting point but the best gauge is to go off your baby’s weight and height.


Washing instructions

Make sure you only opt for onesies that are machine washable. This is non-negotiable.

You are going to be washing A LOT with a baby, there’s no avoiding it, so the last thing you want is to be hand washing. Vomit, poo explosions and leaking nappies are all part and parcel of having a tiny baby, and so you need durable fabrics that can be thrown into the washing machine and will come out looking and feeling exactly like they did when they went in (minus the 💩).

How many should you buy?

This is the big question and many parents will have an opinion on this one. But, before you go buying dozens of outfits, stop and think. Your baby is likely to grow out of the newborn size fairly quickly (normally 2-6 weeks after birth), and some bigger babies don’t even fit in them at all! Or, if your baby comes earlier than expected and is premature, you are going to need to buy some smaller onesies.

So that’s why it’s best to show restraint in this department. We know it’s in our DNA to want to buy ALL the cute things before our baby is born, but instead opt for around 6-10 onesies in 0000 (newborn) and 000 (0-3 months).

That way, once your baby is born and you have an idea of their sizing, you can adjust accordingly. Once upon a time, parents scrambled to get everything they needed before the baby arrived. However, these days with online shopping and Click and Collect, if you decide you need more – or if your baby doesn’t fit the ones you bought them – you can easily grab more.

Have fun!

Now, even though earlier we said to be practical and opt for onesies over tutus and elaborate outfits (for now), that doesn’t mean you can’t still have some fun! Because, after all, dressing your precious bundle in adorable outfits is one of the most exciting parts of new parenthood after, you know, the cuddles and those adorable baby smiles…

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