In children, macroglossia is defined as a resting tongue that protrudes beyond the teeth or the alveolar ridge (Weiss and White, 1990; Weissman et al., 1995). The antenatal diagnosis of macroglossia is somewhat subjective. In the neonate, the tongue grows faster than the other oral structures; it is not limited by the presence of teeth. At rest, some normal neonates may exhibit apparent enlargement of the tongue and protrusion through the lips. For the majority of these newborns, however, the tongue recedes into place with normal anatomic growth of the mouth (Myer et al., 1986). The first scientific report of macroglossia occurred in 1854, when Virchow and Uber described a lingual lymphatic malformation that arose from dilation of lymphatic spaces in the tongue (Vogel et al., 1986).

Vogel et al. (1986) have defined two types of macroglossia: “true” and “relative.” True macroglossia means that histologic abnormalities of the tongue are present that correlate with the clinical findings of tongue enlargement. Examples of such findings include vascular malformations, muscular hypoplasia, tumor infiltrate, or the presence of abnormal elements within the tongue, including edema, inflammation, or storage material. In Beckwith–Wiedemann syndrome, the histology of the tongue is normal, and the macroglossia is due to hyperplasia of the muscle fibers. In lymphangioma, histologic analysis reveals numerous endothelial-lined cystic spaces that contain lymphatic fluid, erythrocytes, and lymphocytes in a thin stroma of connective tissue. The striated muscle in the tongue subsequently atrophies where compression has occurred from dilated lymphatics (Rice and Carson, 1985). Relative macroglossia means that there is apparent tongue enlargement, but no histologic changes within the tongue are demonstrated. An example of relative macroglossia is in trisomy 21, in which the tongue is normal but appears large due to mandibular or maxillary underdevelopment or generalized oropharyngeal hypotonia.

Macroglossia is a rare fetal finding (Weissman et al., 1995). To our knowledge, there are no published reports of the true incidence of macroglossia presenting in utero. An estimate of the incidence of macroglossia may be calculated indirectly from the incidences of three common conditions that are associated with macroglossia—Beckwith–Wiedemann syndrome, congenital hypothyroidism, and trisomy 21. The incidence of Beckwith–Wiedemann syndrome is 1 in 13,500 births (Patterson et al., 1988). Approximately 82% to 99% of infants with Beckwith–Wiedemann syndrome have macroglossia (McManamny and Barnett, 1985; Elliott and Maher, 1994). Taking the more conservative estimate of macroglossia in Beckwith–Wiedemann syndrome (82%), this would give an approximate incidence of 1 in 16,000 livebirths with macroglossia due to Beckwith–Wiedemann syndrome. Overall, trisomy 21 occurs in 1 in 1000 livebirths. Approximately 8.9% of fetuses with trisomy 21 have macroglossia (Weissman et al., 1995). This would give a livebirth incidence of macroglossia due to trisomy 21 of 1 in 11,000. Congenital hypothyroidism occurs in 1 in 5,000 livebirths (Kourides et al., 1984). Approximately 20% of newborns with hypothyroidism have macroglossia (Grant et al., 1992). This would equal a livebirth incidence of 1 in 25,000 livebirths with hypothyroidism and macroglossia. Summation of these studies gives a range of 1 in 11,000 to 1 in 25,000 livebirths presenting with macroglossia as a symptom.

The tongue can be successfully imaged by an inferior coronal view of the fetal face. The tongue can also be visualized by the sagittal profile face view, if the tongue is extending from the mouth (Figure 27-1A) (Weissman et al., 1995). Fetuses with macroglossia have a large protruding tongue (Figure 27-2A). In normal fetuses, the growth of the tongue is linear between 13 and 18 weeks of gestation (Bronshtein et al., 1998). Although nomograms have been published for both first and second trimester fetal tongue size (Achiron et al., 1997; Bronshtein et al., 1998), the diagnosis is usually subjective. Additional sonographic findings include polyhydramnios due to impairment in fetal swallowing. Considerations in the further assessment of fetuses with macroglossia include a detailed search for associated anomalies. Specifically, it is important to rule out fetal goiter (Kourides et al., 1984). A large for gestational age fetus with polyhydramnios might also suggest maternal diabetes, or one of the overgrowth syndromes (see Chapter 124). A macrosomic fetus with macroglossia and other findings, such as omphalocele, increased abdominal circumference, adrenal gland cyst, nephromegaly, and cardiovascular abnormalities, is most likely to have Beckwith–Wiedemann syndrome (Cohen, 2005). Table 27-1 summarizes the prenatal ultrasonographic findings in six cases of Beckwith–Wiedemann syndrome. Macrosomia due to Beckwith–Wiedemann syndrome is a constant finding and can be diagnosed between 16 and 22 weeks of gestation (Viljoen et al., 1991). Prenatal diagnosis of Beckwith–Wiedemann syndrome has been reported at 19 weeks of gestation (Winter et al., 1986), 28 weeks of gestation (Wieacker et al., 1989), and 30 weeks of gestation (Cobellis et al., 1988). Prenatal sonographic diagnosis is not always conclusive for this condition. Even in the setting of a positive family history and multiple prenatal sonograms, the diagnosis was missed in a fetus who presented with severe hydronephrosis, cardiomegaly, and hepatomegaly in utero (Nowotny et al., 1994). Furthermore, there is clinical overlap between Beckwith–Wiedemann syndrome and an X-linked overgrowth syndrome, Simpson Golabi Behmel syndrome (DeBaun et al., 2001).

An additional important consideration in fetal sonographic assessment of macroglossia is the possibility of lingual lymphatic malformations, often seen in association with other lymphatic malformations, such as cystic hygroma. Prenatal sonographic assessment should also specifically exclude abnormalities associated with trisomy 21, such as shortening of the long bones, an increased nuchal fold, cardiovascular defects, widening of the space between the first and second toes, and renal pyelectasis.