Why are clothing size brackets quite wide? Between sizes?

Premature baby clothing sizes use wider weight brackets because weight alone isn’t a precise predictor of body shape, and premature babies grow fast and unevenly in the early weeks.

• Babies carry weight differently. Two babies who both weigh 4lb can have very different proportions (length, torso, leg length, head size), especially if one is early-preterm and one is growth-restricted but closer to term.
• Gestational age matters as much as weight. A 32-week baby and a 36-week baby might weigh the same, but their body composition and proportions can differ a lot.
• Growth is rapid. In NICU and the first weeks at home, babies can move through sizes quickly. Wider ranges mean the garment still fits comfortably through a growth spurt instead of becoming obsolete in days.
• Clothing needs to accommodate medical care. Preterm garments often allow room for nappies, monitors, leads, lines, and easier access for checks. That “extra” can make the fit feel a bit broader by design.
• Manufacturing practicality. Making very narrow size increments would create lots of near-identical SKUs, higher costs, and worse availability—especially for the smallest sizes.

 

Why it’s OK (and often better)

• Better longevity: A 3lb–5lb item can fit well at 3lb and still be wearable as baby approaches 5lb, so you get more use out of each piece.
• Comfort over “perfect tailoring”: For premature babies, softness, ease of dressing, and non-restrictive fit matters more than a super precise size.
• Layering helps: Prem babies are usually dressed in layers (vest + sleepsuit + cardigan/blanket as advised). Slight flexibility in fit is normal and safe.
• You can fit by length and proportions: If a baby is long for their weight, you may size up; if they’re petite/short, you may stay in the lower bracket even if they’re near the top weight-wise.

 

Simple rule of thumb for choosing between sizes

• If baby is near the top of a bracket or is long, go up.
• If baby is near the bottom or looks swamped in the limbs, go down.
• If baby has lines/leads or you want easier changing, err slightly bigger for access and comfort.