Pavlik harness sizing is based on chest circumference, not age or weight alone. A chunky two-month-old and a slim five-month-old can need the same size.
Measuring takes thirty seconds and prevents the most common ordering mistake.
How to measure
- Lay your baby on their back, calm and ideally in just a nappy.
- Pass a soft tape measure around the chest, directly under the armpits.
- Keep the tape level all the way round and snug but not compressing.
- Take the reading at the end of a normal breath out.
- Measure twice. If the two readings differ, use the larger one.
Our size ranges
- Small — chest 33-38 cm, roughly 0-3 months, 3.0-5.5 kg.
- Medium — chest 38-44 cm, roughly 3-6 months, 5.5-8.0 kg.
- Large — chest 44-50 cm, roughly 6-9 months, 8.0-10.5 kg.
If your baby is between sizes
Choose the larger size. The straps adjust down considerably, and babies in the first six months gain chest circumference quickly — a harness that fits perfectly today can be at the top of its range in a month. A slightly larger harness set correctly is safe; a harness that has run out of adjustment is not.
Signs the size is wrong
- The chest strap is on its last adjustment hole or nearly so.
- Webbing ends are so long they need folding repeatedly to stay out of the way.
- Persistent red marks in the same place despite correct tension.
- The stirrups cannot reach the correct foot position without maximum extension.
Growth during treatment
Expect strap adjustments at every clinic review — that is the normal rhythm of treatment, not a sign anything is wrong. Most babies complete a full course in one harness size; babies starting at the top of a range near the end of a size band sometimes need to move up once.
Never adjust the straps yourself between reviews unless your clinic has specifically taught you which strap to move and by how much.
Frequently asked questions
What size Pavlik harness do I need?
Measure chest circumference under the armpits: 33-38 cm is Small, 38-44 cm Medium, 44-50 cm Large. If you fall between two sizes, choose the larger.
Can I size by age instead?
Age is only a rough guide. Chest circumference is the measurement that determines fit, especially for premature babies or larger newborns.
Will my baby need a second size during treatment?
Usually not. Most complete treatment in one size, with straps let out at clinic reviews as the baby grows.