Which craniofacial characteristic is indicative of fetal alcohol syndrome (FAS)?

The thin upper lip is a key craniofacial characteristic associated with fetal alcohol syndrome (FAS). This trait, along with a smooth philtrum and small palpebral fissures, forms part of the classic facial features observed in individuals with FAS. The thin upper lip indicates altered development of the facial structures due to the teratogenic effects of alcohol on the fetus during critical periods of growth.

Recognizing this feature is crucial for early diagnosis and intervention, which can significantly impact the management and support provided to affected individuals and their families. The other options, although they may describe facial features that occur in various conditions, are not characteristic of FAS and do not reflect the typical manifestations seen with this syndrome.