Micrognathia and glossoptosis may cause severe respiratory and feeding difficulties in newborns with Pierre Robin syndrome. The growth of the mandible is alleged to more or less "catch up" during the first year of life. We could not objectify such a catch-up growth using the noninvasive and harmless measurement of the jaw index. The jaw index is defined as alveolar overjet x maxillary arch/mandibular arch. The alveolar overjet is the frontodorsal distance between the most anterior points of the upper and lower alveolar arches, whereas the maxillary arch is measured from the left tragus to the right tragus via the subnasal point, and the mandibular arch is measured from the left to the right tragus via the pogonion point. The growth of the mandible in 7 Pierre Robin patients was found to be proportionately similar to that observed in healthy control subjects age 0 months (N = 100), 6 months (N = 42), and 1 year (N = 32).