Your baby's NHS Personal Child Health Record growth chart will have half of boys reaching 20lbs at 39 weeks (8 months) and half of girls at 46 weeks (10 months). So our size 1 nappies will fit most newborn babies up to around 9 months. If your baby has a low birth weight the size 1 nappies will not fit until they reach around 7lbs as the leg elastic will be baggy and will affect containment.
For 20lbs (or around 9 months onwards) until potty your baby will need our size 2 nappies.