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

Smooth philtrum and thin upper lip are classic facial features of FASD, resulting from prenatal alcohol exposure affecting facial development. Other options describe features not characteristic of FASD.

Correct Answer: 1. Smooth philtrum and thin upper lip

The assessment of a newborn with a history of prenatal alcohol exposure (PAE) relies heavily on identifying characteristic dysmorphic facial features. The combination of a smooth philtrum (the vertical groove between the nose and upper lip) and a thin upper lip (specifically, a thin vermilion border) represents two of the three cardinal facial features used in the diagnosis of fetal alcohol spectrum disorder (FASD) ^[3][4].

Why This Is the Most Characteristic Finding

Diagnostic guidelines for FASD consistently identify a specific triad of sentinel facial anomalies: short palpebral fissures, a smooth philtrum, and a thin upper lip ^[3][4]. These features reflect the teratogenic disruption of embryonic development during the first trimester, when alcohol exposure interferes with the migration and proliferation of neural crest cells that form the midline structures of the face ^[1]. The presence of these dysmorphic features, particularly when combined with confirmed PAE and neurodevelopmental deficits, forms the basis for diagnosing Fetal Alcohol Syndrome (FAS), the most severe end of the FASD spectrum ^[3].

A prospective longitudinal study confirmed that children with substantial PAE exhibit these dysmorphological phenotypes, which remain identifiable and consistent at 6 years of age ^[1]. Furthermore, research examining the facial shape of children aged 6 to 8 years demonstrated that even low to moderate levels of PAE can produce subtle but persistent changes in facial morphology, including midface hypoplasia, which contributes to the appearance of a smooth philtrum ^[2]. This underscores the sensitivity of facial development to alcohol's teratogenic effects and the reliability of these features as clinical markers.

Analysis of Incorrect Options

Option 2: Macrocephaly and large fontanelles
This finding is not characteristic of FASD. Prenatal alcohol exposure typically results in microcephaly (head circumference below the 10th percentile), not macrocephaly, due to impaired brain growth ^[3][4]. The dysmorphological assessments in the prospective cohort study focus on growth deficiency and structural brain abnormalities consistent with reduced head size, not enlargement ^[1].

Option 3: Webbed neck and low-set ears
These features are more commonly associated with chromosomal abnormalities such as Turner syndrome or Noonan syndrome. The diagnostic guidelines for FASD do not include a webbed neck or low-set ears as part of the characteristic facial phenotype. Instead, the focus is on midface hypoplasia, epicanthal folds, and a flat nasal bridge in addition to the cardinal features ^[4].

Option 4: Prominent nasal bridge and large eyes
This option describes features opposite to those seen in FASD. Children with PAE typically present with a flat or low nasal bridge and short palpebral fissures (small eye openings), not a prominent nasal bridge or large eyes ^[3][4]. The Canadian diagnostic guidelines explicitly list short palpebral fissures as one of the three cardinal facial features, and a depressed nasal bridge is a commonly associated finding ^[3]. The facial shape analysis in children with PAE confirmed a retrusion of the midface and nasal region, which would manifest clinically as a flatter profile ^[2].