What to choose between size 1 or 2 diapers when baby is born?

In collaboration with Rokiyah Hosen

Relecture professionnelle

There's a lot to think about when you're expecting a baby, especially when it's your first! Among these many supplies are the famous diapers. Figuring out how many diapers you're going to need, how many packages, what to stock up on in advance, etc. can be a real headache... And that's not counting the diaper size thing! In this article, we explain what you need to bear in mind when choosing the right size for baby's birth!

What are the differences between size 1 and 2 diapers?

There are two different diaper sizes to suit the birth of your baby: size 1 and size 2.

Size 1 diapers

The size 1 diaper is designed for newborns weighing from 2 to 5 kg, up to around two months of age. This is the smallest diaper size available.

Size 2 diapers

The size 2 diaper is suitable for babies weighing between 3 and 6 kg, and can be used up to 3 to 4 months. However, depending on the baby's weight and size at birth, size 2 diapers can be used from birth or shortly afterwards.

Verdict: which diaper size to choose when baby is born?

As you can see, the two sizes overlap in terms of weight. This makes it difficult for parents to choose the right diaper.

We advise you to wait for the last ultrasound before buying diapers for your baby. In fact, it's at the last ultrasound that you'll find out your baby's expected weight. And weight is one of the factors that will help you choose the right size for your diapers.

The second factor to take into account when choosing a diaper size is morphology. But this is difficult to predict in advance!

In any case, you'll need a pack of size 1 diapers for your stay in the maternity ward, i.e. for the first few days of baby's life. Even if your baby is expected to weigh 4 kg. The average maternity stay lasts 3 to 5 days. You'll only need one or two packs of size 1 diapers. If your baby weighs 4 kg or more, a single pack of size 1 will suffice, and when you get home you can switch straight to size 2.

During the first few days of his life, your baby will lose weight (around 10% of his birth weight). This is perfectly normal, as he loses water as he eliminates his meconium (the first stools). The amount of milk he drinks, on the other hand, is very low.

Your baby will regain his birth weight after 1 to 2 weeks. This is why size 1 diapers are essential for all babies, even if you only need one pack.

For smaller babies or premature babies, there is a size 0, but very few brands offer it. This size corresponds to babies weighing between 1 and 2.5 kg. As your baby grows, you can start with size 1.

When to change baby's diaper size?

Generally speaking, size 1 diapers are only needed for the first few days of your baby's life , while he's in the maternity ward. When you return to the maternity ward, depending on your baby's weight and morphology, you can switch to the next size up, size 2. There's no need to stock up on size 1 diapers!

Here are a few signs that it's time to move up to the next size:

  • If you notice recurrent leaks and an overflowing diaper;
  • If, when you change your baby, you notice red marks on the skin around the diaper waistband or thighs, this means that the diaper is too tight and potentially too small;
  • If you have trouble closing the diaper's elastics, or if they tend to come loose.

When it comes to diapering, you need to change your baby after every feed or bottle, and as soon as he or she has had a bowel movement. It's important to change your baby regularly to avoid any kind of irritation, diaper rash or redness.

How to choose the right diaper for your baby?

Choosing the right size diaper is vital for your baby's well-being, as he'll be wearing them for a long time before he's potty-trained.

But to choose a quality diaper for your baby, it's important to consider more than just size. Diapers are in direct contact with your baby's skin, which is highly sensitive and permeable. So it's important to look at :

Diapers without ultra-chemical composition

The composition of the diaper. All the more so when you consider that, a few years ago, 60 millions de consommateurs revealed the presence of toxic substances in many baby diapers.

The Agence Nationale de la Sécurité Sanitaire (French National Agency for Health Safety) then looked into the composition of disposable diapers and came to the same conclusion, namely that there are indeed chemical substances hazardous to the health of newborns, present in many diaper references and even exceeding authorized health thresholds.

Nobody wants to put their baby in toxic diapers. So, to avoid chemical substances, we recommend that you choose organic cotton diapers.

To ensure that the ecological and organic diaper you choose for your baby is safe, there are several things you can refer to:

  • The manufacturing process: most disposable diapers bleach the cellulose with chlorine dioxide using the ECF (Elementary Chlorine Free) method. 5% of diapers (ecological diapers) are bleached using the TCF (Totally Chlorine Free) method, which is the most human-friendly method, since it uses no chlorine or chlorine dioxide compared with the ECF method. For a high-quality, baby-friendly diaper, choose the TCF method;
  • An ecological diaper brand that's healthy for your baby's skin must be transparent about its composition and manufacturing methods, and chemical analysis reports must be accessible. If you can't find the chemical analysis reports, it's not a very good sign;
  • Organic diapers must not contain toxic residues, harmful or undesirable substances or carcinogens such as glyphosate, volatile organic compounds, dioxins, furans, perfumes, pesticides, allergens or latex (in the elastics);
  • For a healthy, respectful diaper, endocrine disruptors are also to be avoided;
  • A good ecological diaper also favors natural raw materials, which are softer and more comfortable for your baby's bottom, but also more respectful of the environment. The most important thing is that your baby's skin should be in direct contact with natural, biodegradable materials made from natural fibers, rather than plastic. Look at the composition of your diaper and the percentage of natural fibers!


Having a diaper with impeccable absorbency is very important for your baby's comfort and to avoid leaks. Ecological diapers are just as absorbent as chemical diapers. They generally add natural cellulose to the absorbent layer, as they reduce the amount of SAP (sodium polyacrylate, an absorbent synthetic material with no more natural alternative) absorbent beads.

Choosing the right diaper for your baby means choosing a diaper that's the right size for him, healthy and respectful of his skin, absorbent and comfortable.

FAQs on size 1 or 2 birth diapers

When should I change from size 1 to size 2 diapers?

Size 1 diapers are suitable for the first few days of your baby's life. Depending on weight and morphology, you can switch to size 2 more or less when you return home from the maternity hospital.

How do I know if my baby's diapers are too small?

If you notice leaks, red marks on your baby's skin and you have trouble getting the elastic to stay in place: his diaper is probably too small.