A nurse is assessing a newborn whose mother consumed alcohol during pregnancy. Which finding would be most characteristic of fetal alcohol spectrum disorder (FASD)?

The classic triad of sentinel facial anomalies in Fetal Alcohol Spectrum Disorder (FASD) includes a smooth philtrum, thin upper lip (thin vermilion border), and short palpebral fissures. These result from alcohol's disruption of neural crest cell migration during the first trimester.

A smooth philtrum is assessed by visualizing the groove between the nose and upper lip, noting the absence of the normal ridges. A thin vermilion border is measured or compared to standardized lip-thinness guides. These features, combined with confirmed prenatal alcohol exposure and neurodevelopmental deficits, form the basis for diagnosing Fetal Alcohol Syndrome (FAS).