Adjustable bangles generally slide together or apart, to create a smaller or larger bangle. This means most of this style of bangle can be purchased for a newborn, and adjusted to fit, then as she grows, made larger. A great way to get even better value from the gift.
Baby bracelets are very popular for newborn gifts and most come with at least one extra jump ring on an extension so that the bracelet can fit the tiniest of babies right through their rapid growth stage, until age 4, 5 or more.
Solid baby bangles are probably the safest of baby jewellery and for that reason are very popular. But you can buy adjustable bangles that will last for years during their fastest growth stage.