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Clinical Outcome of Fetuses With Sonographic Diagnosis of Isolated Micrognathia

From the Department of Obstetrics and Gynecology, Department of Pediatrics, and Division of Fetal Imaging, William Beaumont Hospital, Royal Oak, Michigan.

Address reprint requests to: Ivana M. Vettraino, MD, William Beaumont Hospital, Department of Obstetrics and Gynecology, Division of Fetal Imaging, 3601 West Thirteen Mile Road, Royal Oak, MI 48073-6769; E-mail: ivettraino{at}beaumonthospitals.com.

	ABSTRACT

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OBJECTIVE: To describe the clinical outcome of fetuses with the prenatal sonographic diagnosis of isolated micrognathia.

METHODS: A retrospective review of fetuses and infants with the prenatal diagnosis of isolated micrognathia for April 1990 to August 2001 was undertaken. Isolated micrognathia was considered if no other anatomic, growth, or amniotic fluid abnormalities were detected by a detailed ultrasound examination. Sources of outcome data included maternal and neonatal medical records, prenatal genetics records, and karyotype results.

RESULTS: Fifty-eight fetuses with the diagnosis of micrognathia were identified. Fifteen fetuses (26%) had isolated micrognathia by prenatal sonogram. After neonatal examination, 14 of 15 were found to have at least one additional abnormality. Eleven had a cleft of the soft and/or hard palate. Seven (54%) of 13 live-born neonates had mild to severe airway obstruction that required intervention. Four (31%) of 13 experienced feeding difficulties of varying duration. Follow-up data were available for 1 to 10 years. Eight (62%) of 13 children are reported to be doing well. Five (38%) of 13 children are reported to have mild to severe developmental delay.

CONCLUSION: If micrognathia is the only sonographic finding identified, physicians and families should be prepared for possible respiratory difficulty at delivery, the presence of a cleft palate, and/or developmental delay. ( Obstet Gynecol 2003;102:801–5[Abstract/Free Full Text]. © 2003 by The American College of Obstetricians and Gynecologists.)

The term "micrognathia" refers to a small receding chin resulting from an underdeveloped or hypoplastic mandible. A characteristic midsagittal profile may be observed during prenatal sonographic examination of the fetus. Although this problem can be isolated, association with numerous syndromes and karyotypic abnormalities is well reported. In these cases, the clinical outcome and prognosis tend to be dictated by the associated anomalies.

Previous sonographic studies have described the prenatal diagnosis and immediate perinatal outcome for newborns with micrognathia.^1,2 These studies, however, have included cases identified in prenatal sonograms with and without isolated micrognathia. Furthermore, little information exists regarding how these infants do in the perinatal period and after discharge from the hospital. This investigation summarizes our prenatal experience with isolated micrognathia. The perinatal course and clinical outcome of these affected infants are emphasized.

	MATERIALS AND METHODS

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A retrospective review of all fetuses and infants with congenital micrognathia was undertaken at our institution with approval from the Human Investigation Committee. Pertinent sonographic findings and neonatal outcome were derived from our computer database for April 1990 to August 2001. Medical records of newborn infants with the diagnosis of micrognathia (International Classification of Diseases, 9th revision, codes 524.04 and 756.0) were also cross-referenced with our search results to optimize the likelihood that all relevant cases had been identified. Only fetuses scanned in the Fetal Imaging Unit and delivered in our hospital were included in the data analysis. Other outcome data sources included the maternal medical record, child’s medical record, cytogenetics laboratory reports, and the prenatal genetics records. The Pediatric Genetics Division uses a five-page questionnaire completed at each follow-up visit that investigates developmental milestones, hospitalizations, complications, and general health.

Before 1997, our ultrasound unit did not include evaluation of the fetal facial profile for low-risk pregnancies. However, the facial profile has always been a required view for targeted fetal evaluations and if other anatomic abnormalities were observed. The fetal facial profile was subsequently added to our anatomic checklist for fetuses of more than 13 menstrual weeks. Patients were not asked to return if a midsagittal view of the face was not obtained as a result of technical reasons. When technically feasible, we attempted to visualize the fetal facial profile from a midline sagittal scanning plane. Micrognathia was suspected when the upper lip appeared prominent and the chin appeared small, absent, or receding. The diagnosis of micrognathia was a subjective diagnosis suspected by the sonographer and confirmed by the physician. A diagnosis of isolated micrognathia was considered if no other anatomic, growth, or amniotic fluid abnormality was identified by prenatal sonogram.

Patients carrying a fetus with suspected isolated micrognathia were offered genetic consultation and genetic amniocentesis. If the patient declined amniocentesis, then karyotype analysis was performed after delivery if dysmorphic features were confirmed. In addition, pediatric genetics consultation was requested in the neonatal period if dysmorphic features were present.

During the study period, ultrasound equipment consisted of the Acuson 128XP/10, Acuson XP, Acuson Sequoia (Acuson Corp., Mountain View, CA), Aloka 650 (Corometrics Ultrasound Medical Systems, Wallingford, CT), Phillips Platinum (Phillips Medical System, Santa Ana, CA), Voluson 530D, and Voluson 730 (General Electric Medical Systems, Milwaukee, WI). Sonography was performed by experienced sonographers with 2 to 15 years’ dedicated fetal imaging experience and reviewed by an obstetrician with subspecialty training in radiology or maternal–fetal medicine. Cases of abnormal findings detected at the time of prenatal ultrasonography were customarily presented at a weekly meeting of the physician members of the division. The findings were discussed, and a consensus on diagnosis and follow-up was reached.

	RESULTS

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Our ultrasound unit performed 172,988 scans for 94,230 patients during the study period. Fifty-four fetuses with the diagnosis of micrognathia were identified by prenatal ultrasonography. An additional eight fetuses, which had been examined in the ultrasound unit but had not received a prenatal diagnosis of micrognathia, were identified by hospital chart review. Four fetuses were excluded from the review because they did not deliver at our hospital, leaving a total of 58 fetuses for evaluation.

Each pregnancy underwent 3.5 ± 2.0 (range, 1–11) sonographic examinations, with the initial diagnosis being made at 20.5 ± 4.7 (range, 16.5–38.4) menstrual weeks. Most fetuses (n = 39, 67%) were referred for evaluation of fetal growth. The remaining 19 (33%) were referred for specific indications: fetal echocardiography for family history of cardiac abnormality (n = 3), suspected multiple fetal anomalies (n = 4), suspected fetal intracranial abnormality (n = 3), abnormal second-trimester maternal serum screening (n = 2), elevated maternal serum alpha-fetoprotein (n = 1), suspected cardiac abnormality (n = 1), third-trimester hydramnios (n = 1), second-trimester oligohydramnios (n = 1), cleft lip (n = 1), clubfoot (n = 1), and known trisomy 18 (n = 1).

Fifteen (26%) had no other abnormalities identified during the prenatal ultrasound examinations and were classified as having isolated micrognathia. One patient terminated her pregnancy. One pregnancy ended when the fetus died. After neonatal examination of 13 live-born infants and the two autopsy examinations, 14 (93%) of 15 of these infants were found to have additional abnormalities. Just one infant had true isolated micrognathia.

Table 1 summarizes the neonatal findings and the available outcome data. The majority of these additional abnormalities were clefts of the soft and/or hard palate. Of note, seven (54%) of 13 neonates had airway obstruction requiring intervention, including two tracheotomies and two intubations. Four (31%) of 13 neonates had initial and/or prolonged feeding difficulties. Three of 15 neonates had a syndrome (cerebrocostomandibular), an association (CHARGE, or coloboma, heart anomaly, choanal atresia, retarded growth, genital hypoplasia, and ear anomalies/deafness), or a chromosomal abnormality (mosaic trisomy 9) identified in the neonatal period. In the follow-up period between 12 months and 10 years (median, 2 years), seven (54%) of 13 children had no reported complications, and five (38%) of 13 children had mild to severe developmental delay. Of the seven children without reported complications at time of last follow-up, five (71%) underwent procedures for the surgical correction of cleft palate, and four (57%) underwent surgical procedures for separate and distinct indications.

	DISCUSSION

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Micrognathia can occur as an isolated entity or as a part of an underlying fetal karyotypic or syndromic abnormality.³ This study, in agreement with others, found that a majority of fetuses will have other anatomic anomalies and that these additional abnormalities tend to be predictive of a poor outcome. In cases of a prenatal diagnosis of isolated micrognathia, one could assume that the prognosis would be more favorable. Our 10-year review, however, found that 93% of fetuses with a prenatal diagnosis of isolated micrognathia had additional anomalies (which eluded sonographic detection) and neonatal complications. Clefts of the soft and/or hard palate were a common unidentified anomaly, observed in 11 (73%) of 15 cases. Fifty-four percent of the newborns had mild to severe respiratory compromise requiring immediate attention and intervention. One-third of the newborns had initial feeding difficulties requiring varying degrees of intervention. Thirty-eight percent experienced developmental delay.

The commonly observed association of micrognathia and varying degrees of cleft palate observed in our cases of micrognathia can be explained by a description of the embryology. The primary and secondary palate develops from a segment of the maxilla between the fifth and 12th weeks of fetal development.^4,5 Normally, as the mandible develops, the tongue decreases in relative size and falls to an inferior position within the fetal mouth. Failure of mandibular growth displaces the tongue upward, which in turn prevents the lateral palatine shelves from medial migration and midline fusion.⁵ The etiology of the mandibular hypoplasia is unclear and may result from a positional malformation, an intrinsic growth abnormality, a neurologic abnormality, or a connective tissue disorder.⁶ Sonographic visualization of cleft palate appears to be limited to abnormalities of the anterior palate, which would involve disruption of the alveolar tooth buds.^7–9 Posterior clefts have not been visualized during prenatal sonographic examinations. Clefts involving disruption of the maxillary tooth buds are more easily identified.

The sonographic diagnosis of fetal micrognathia has been largely subjective. The incidence of micrognathia is estimated to be small in a primarily low-risk obstetric population. In this study population, the incidence is 1 per 5000 for prenatal isolated micrognathia. Nomograms for mandibular lengths at varying gestational ages have been published.^10–12 These nomograms may help with an objective evaluation of the fetal chin if there is an initial suspicion of a small chin.

Our short- and long-term outcome data showed that 38% of survivors had some form of developmental delay. These sequelae varied from mild speech delays to severe developmental delay. Sixty-two percent of the live-born children are reportedly without complications at the time of most recent follow-up available for review. Of these cases, however, six (86%) of seven have still required some surgical intervention. Thus, despite the paucity of prenatal sonographic findings, short- and long-term interventions are likely for some children with the prenatal diagnosis of isolated micrognathia.

The prenatal identification of micrognathia may therefore be the only predominant sonographic finding in the prenatal period despite the presence of an underlying genetic disorder. Syndromes in which micrognathia may be the most marked sonographic finding are described below.

Pierre Robin sequence (PRS) can be isolated or observed as a feature of a syndrome. Micrognathia, glossoptosis, and cleft palate characterize PRS. The majority of the affected children have a wide U-shaped cleft palate. Initially, respiratory and feeding difficulties can occur as a result of the proportionally large tongue and the palate abnormality. The mandible can grow in time to accommodate the tongue. These children may need to undergo many surgical procedures.¹³ In general, children with isolated PRS do not have developmental delay.

Cerebrocostomandibular syndrome has a characteristic rib-gap abnormality. Rib gaps occur between the costovertebral junction and the lateral arc, most commonly affecting the third to seventh thoracic segments; flail chest results. Hypoplasia of the sternum and clavicles can also be observed. Developmental delay is a known component of this syndrome.¹⁴

The CHARGE syndrome has mental retardation and developmental delay as an important component. Examples of other syndromes in which micrognathia may be the only important prenatal ultrasound finding include Smith-Lemli-Opitz, Cornelia De Lange, ear patella short stature, Catel-Manzke, Stickler, Treacher Collins, Ehlers-Danlos type 7, hyaloideoretinal degeneration of Wagner, and FG. Developmental delay is a noteworthy feature of micrognathia and may be the only significant prenatal ultrasound finding for Smith, Cornelia De Lange, Catel-Manzke, and FG.¹⁴

The role of three-dimensional (3-D) ultrasounds in the diagnosis of micrognathia requires further clarification.^6,9,15,16 One advantage of the 3-D evaluation is to provide a true midline sagittal view of the fetal face. 3-D ultrasounds have been recently described for the evaluation of fetal micrognathia.⁹ Multiplanar views provide the examiner with a true midline sagittal plane of the facial profile. This is particularly useful because it minimizes the possibility of making a false diagnosis of micrognathia if an oblique scanning plane is mistakenly used. Rotten and colleagues¹⁵ have also applied semi-quantitative diagnostic criteria for the evaluation of the fetal mandible. By means of 3-D sonograms, they developed a ratio of the mandible width to maxilla width to characterize abnormalities of the fetal mandible. Of the patients in our study that underwent both conventional and 3-D ultrasound examinations, there was only one false-negative diagnosis by conventional imaging. Thus, this risk may be more theoretical than real. Ghi et al⁶ have retrospectively compared conventional sonogram with 3-D ultrasound for the diagnosis of a variety of cases of craniofacial abnormalities referred to their center. The authors concluded that two-dimensional ultrasound was accurate in the specific diagnosis of craniofacial abnormalities.

In summary, a prenatal diagnosis of micrognathia requires a detailed evaluation of the fetus, genetic consultation, and special preparation for delivery should emergent intervention be necessary because of airway obstruction. Our results suggest that even if isolated micrognathia is the only sonographic finding identified, families must be prepared for the possibility of additional findings and possible underlying syndromes, associations, or karyotypic abnormalities once the neonatal examination can be performed. The long-term outcome for this seemingly isolated finding may be more guarded than one would intuitively believe.

	Footnotes

 
doi:10.1016/S0029-7844(03)00672-0

Received March 10, 2003. Received in revised form May 7, 2003. Accepted June 5, 2003.

	REFERENCES

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1. Bromley B, Benaceraff BR. Fetal micrognathia: Associated anomalies and outcome. J Ultrasound Med 1994;13: 529–33.[Abstract]

2. Nicolaides KH, Salvesen DR, Snijders RJM, Gosden CM. Fetal facial defects: Associated malformations and chromosomal abnormalities. Fetal Diagn Ther 1993;8:1–9.

3. Kennett S, Curran JB. Mandibular micrognathia: Etiology and surgical management. J Oral Surg 1973;31:8–17.[Medline]

4. Sherer DA, Metlay LA, Woods JR. Lack of mandibular movement manifested by absent swallowing: A possible factor in the pathogenesis of micrognathia. Am J Perinatol 1995;12:30–3.[Medline]

5. St-Hilaire H, Buchbinder D. Syndromic and other congenital anomalies of the head and neck: Maxillofacial pathology and management of Pierre Robin sequence. Otolaryngol Clin North Am 2000;33:1241–58.[Medline]

6. Moore KL, Persaud TVN. The developing human: Clinically oriented embryology. 5th ed. Philadelphia: WB Saunders, 1993:216–22.

7. Ghi T, Perolo A, Banzi C, Contratti G, Valeri B, Savelli L, et al. Two-dimensional ultrasound is accurate in the diagnosis of fetal craniofacial malformation. Ultrasound Obstet Gynecol 2002;19:543–51.[Medline]

8. Babcock CJ, McGahan JP. Axial ultrasonographic imaging of the fetal maxilla for accurate characterization of facial clefts. J Ultrasound Med 1997;16:619–25.[Abstract]

9. Lee W, Kirk JS, Shaheen KW, Romero R, Hodges AN, Comstock CH. Fetal cleft lip and palate detection by three-dimensional ultrasonography. Ultrasound Obstet Gynecol 2000;16:314–20.[Medline]

10. Watson WJ, Katz VL. Sonographic measurement of the fetal mandible: Standards for normal pregnancy. Am J Perinatol 1993;10:226–8.[Medline]

11. Chitty LS, Campbell S, Altman DG. Measurement of the fetal mandible-feasibility and construction of a centile chart. Prenat Diagn 1993;13:749–56.[Medline]

12. Paladini D, Tiziana M, Teodoro A, Lamerti A, Tremolaterra F, Martinelli P. Objective diagnosis of micrognathia in the fetus: The jaw index. Obstet Gynecol 1999;93: 382–6.[Abstract/Free Full Text]

13. Witt PD, Myckatyn TB, Marsh JL, Grames LM, Dowton SB. Need for velopharyngeal management following palatoplasty: An outcome analysis of syndromic and nonsyndromic patients with Robin sequence. Plast Reconstr Surg 1997;99:1522–9.[Medline]

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15. Rotten D, Levaillant JM, Martinez H, Ducou Le Pointe H, Vicaut E. The fetal mandible: A 2D and 3D sonographic approach to the diagnosis of retrognathia and micrognathia. Ultrasound Obstet Gynecol 2002;19:122–30.[Medline]

16. Lee W, McNie B, Chaiworapongsa T, Conoscienti G, Kalache KD, Vettraino IM, et al. Three-dimensional ultrasonographic presentation of micrognathia. J Ultrasound Med 2002;21:775–81.[Abstract/Free Full Text]

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