What is the difference between First Size, Newborn and Up to 1 month clothes in the UK?

What do First Size, Newborn and Up to 1 month actually mean?

They are marketing names for a body-measurement row, not a legal UK size. Next, George at Asda and Mamas & Papas each publish their own height and weight figures. The same words on a hangtag can point at different kilograms and centimetres once you open the chart.

The NHS notes that babies grow very quickly and that a modest starter set of clothes is enough for the first weeks. It does not define First Size or Newborn. The kg/cm row on the shop you are buying from is the figure that decides the garment.

George gift sets and Next rails often say First Size. Mamas & Papas and John Lewis more often say Newborn. Those are not interchangeable without the chart.

How do the high-street charts compare, shop by shop?

Read each row as that brand's own body measurement. Do not average them into one UK First Size.

Is First Size the same as Newborn?

Only if you stay inside one shop. Next First Size (50 cm / 3.4 kg) sits next to Mamas & Papas Newborn (50 cm / 3.2 kg). George First Size is a larger row: 56 cm and up to 4.1 kg — the same height and weight John Lewis prints for Newborn.

• Next First Size ≠ George First Size. Same words; George's row is 6 cm longer and about 0.7 kg heavier at the top.
• George First Size ≈ John Lewis Newborn on the published cm/kg caps (56 cm / 4.1 kg).
• Mamas & Papas Newborn ≈ Next First Size on height (both 50 cm), with a 0.2 kg gap on the weight figure.

If a gift set says First Size and you already own Newborn vests from another shop, check both charts before you assume they will hang together.

Which label should I buy before the baby arrives?

The NHS and NCT both treat clothing as a small starter set, because size is not known until birth. A late scan weight is an estimate, not a hangtag.

A practical split on the high street is a few pieces on the 50 cm / ~3.2–3.4 kg row (Next First Size or Mamas & Papas Newborn) plus more on the 56 cm row (Next or Mamas & Papas Up to 1 month, or George First Size). That covers a typical full-term range without filling a drawer with one shop's smallest label.

NHS Start for Life lists at least six sleepsuits and four to six vests for a newborn wardrobe. It does not tell you to choose First Size over Newborn. Quantity is the NHS figure; the kg/cm row is the shop's.

How do I read a shop chart without mixing labels?

1. 1
   Find the chart for that brand Open Next Help Centre, the George / Asda baby chart, the Mamas & Papas size guide, or the John Lewis babywear table on the product page. Ignore a hangtag from a different shop.
2. 2
   Read height and weight, not the age words Charts state body measurements. Mamas & Papas says so on the page. A 56 cm baby is on that shop's 56 cm row even if they are two weeks old.
3. 3
   If height and weight disagree, follow the tighter fit A long, light baby will hit the cm cap first (sleepsuits show this at the toes). A short, heavier baby will hit the kg cap first (poppers at the nappy).
4. 4
   Keep the next row ready Next's step after First Size is Up to 1 month (56 cm / 4.5 kg), then Up to 3 months (56–62 cm / 4.5–6 kg). Those are Next rows, not a universal calendar.

In shortFirst Size, Newborn and Up to 1 month only mean the kg and cm printed by that shop. George's First Size matches John Lewis Newborn more closely than it matches Next First Size. Buy from the chart, not the words on the rail.