Significance of chromosome 22q11 analysis after detection of an increased first-trimester nuchal translucency

Prenatal sonographic findings in a cohort of foetuses with a confirmed 22q11.2 microdeletion at a single Chinese Tertiary Centre

The aim of this study was to present prenatal ultrasound findings, molecular testing results and pregnancy outcomes of cases with 22q11.2 deletion (del22q11.2) diagnosed prenatally. A total of 76 foetuses were included. All cases were diagnosed by using chromosomal microarray analysis. Data on prenatal diagnosis, ultrasound findings, pregnancy outcomes and inheritance of del22q11.2 were reviewed. Congenital heart defects (CHDs) were the most common indications (47/76, 61.8%) for prenatal testing and were isolated in 52.6% (40/76). The constitution of CHDs comprised predominantly of conotruncal defects (61.7%; 29/47). Other cardiac anomalies were encountered in 38.3% (18/47) of cases. Extracardiac findings, including unilateral multicystic dysplastic kidney, clubfoot, increased nuchal translucency, intrauterine growth retardation and polyhydramnios, were found in 31.6% (24/76) of cases, and were combined with CHDs in 7 cases. Twelve cases had normal sonographic scans at the time of prenatal diagnosis. Foetal CHDs, especially conotruncal defects, are the most predictive association with del22q11.2. The information about del22q11.2 should also be part of the contents in comprehensive pre-test counselling even for those who are referred for diagnostic testing with foetal extracardiac findings.Impact statementWhat is already known on this subject? 22q11.2 deletion (del22q11.2) is the most common microdeletion syndrome in humans. At present, the main indications for prenatal testing for del22q11.2 are pregnancies of abnormal sonographic findings, especially foetal congenital heart defects.What do the results of this study add? Many extracardiac malformations, including some lethal or mildly non-specific ones, could be associated with foetal del22q11.2. There were also del22q11.2 foetuses had normal sonographic scans at the time of prenatal diagnosis.What are the implications of these findings for clinical practice and/or further research? The information about del22q11.2 should also be part of the contents in comprehensive pre-test counselling even for those who are referred for diagnostic testing with indications other than foetal cardiac anomalies.

Increased nuchal translucency and normal karyotype: perinatal and pediatric outcomes at 2 years of age

OBJECTIVE

To assess the perinatal and pediatric outcomes up to 2 years of age in singleton karyotypically normal fetuses with increased nuchal translucency (NT) above the 99(th) percentile.

METHODS

Singleton fetuses with NT above the 99(th) percentile and normal karyotype scanned in our center from 2002 to 2006 were included. Work-up included first- and second-trimester anomaly scan, first- and second-trimester fetal echocardiography, and in selected cases infection screening and genetic testing. Among survivors, a pediatric follow-up up to 2 years of age was undertaken.

RESULTS

During this 4-year period, 171 singleton fetuses with NT above the 99(th) percentile and normal karyotype were included in the study. There were seven spontaneous fetal losses, 38 terminations of pregnancy and two postnatal deaths. Among the 124 (72.5%) survivors, 12 (9.7%) were born with structural abnormalities. Neurodevelopmental follow-up was completed in 108 (87.1%) of the 124 survivors and four (3.7%) showed moderate to severe impairment. Overall, a structural abnormality or genetic syndrome was diagnosed in 50 fetuses/newborns. Prenatal diagnosis was achieved for 83.8% (31/37) of the structural abnormalities and 69.2% (9/13) of the genetic syndromes. Interestingly, a single umbilical artery was found in six fetuses with no structural defects at birth, five of which had a long-term favorable outcome (4.5%), and in one 22q11 microdeletion syndrome was diagnosed at 2 years of age.

CONCLUSION

Singleton fetuses with an increased NT above the 99(th) percentile and normal karyotype showed a 63% intact survival. Long-term neurodevelopmental outcome among survivors did not appear to differ from that reported for the general population.

Prenatal and postnatal diagnosis of 22q11.2 deletion syndrome

Microdeletion of chromosome 22q11.2, the most common human deletion syndrome encompasses a wide spectrum of abnormalities. Many clinical or ultrasonographic findings may support deletion studies, either in utero or in the post-natal period. The objective of our study was to evaluate the circumstances of 22q11.2 deletion diagnosis in a single centre of genetics during a 12 years period. Testing for 22q11.2 deletion was performed in 883 cases. Congenital heart defect was the most common reason for referral. An antenatal 22q11.2 microdeletion was detected in 8 fetuses (4.7%) among 169 pregnancies, all presenting conotruncal anomalies. In one case prenatal diagnosis led to the identification of the deletion in the mildly affected father and had negative impact on the family. During the same period, postnatal 22q11.2 DS was diagnosed in 81 out of 714 patients aged from birth to 42 years (11.3%) (p = 0.02). A CHD was present in 37 (45.7%). This figure is significantly lower than the 75% commonly reported. These results suggest that deletion studies could be justifiable in fetuses with non-cardiac prenatal sonographic findings that have been reported in association with 22q11.2 DS. However, as most of these malformations are rather common and non specific, systematic 22q11.2 testing is not justifiable. In such cases, careful cardiac and thymus examination could provide additional clues for 22q11.2 testing. In addition parents should be given accurate information before antenatal or postnatal testing, including the wide variability of the clinical phenotype, the impossibility to establish a precise prognosis concerning psychomotor development and psychiatric risks.

Perinatal echocardiography: protocols for evaluating the fetal and neonatal heart

This Protocol for Evaluating the Fetal and Neonatal Heart details the indications, views, and measurements to be obtained for both (1) the basic screening examination of the fetal heart (a necessary component of all complete fetal anatomy evaluations) and the specialty study called (2) echocardiography as applied to either the fetus or neonate, using 2D and Doppler ultrasound. While the purpose of the screening study is to detect or exclude the possibility of a cardiac abnormality, echocardiography attempts to diagnose the specific anatomic and physiologic disruption. Also emphasized is the value of a collaborative team approach to management of the fetus and its parents when a cardiovascular anomaly is present, in an effort to achieve a smoother transition from fetus to neonate across the continuum of perinatal care.

Prospective study of 22q11 deletion analysis in fetuses with excess nuchal translucency

OBJECTIVE

The purpose of this study was to determine the frequency of 22q11 deletions (DiGeorge, velocardiofacial syndromes) in chromosomally normal fetuses with excess nuchal translucency.

STUDY DESIGN

We evaluated chorionic villus sampling (CVS) samples submitted with an indication of excess nuchal translucency. If chromosome analysis was normal, permission was obtained to perform 22q11 microdeletion fluorescence in situ hybridization analysis. By Fisher exact test, the null hypothesis that there is no association between excess nuchal translucency and 22q11 deletions was tested.

RESULTS

Among 239 CVS samples from fetuses with excess nuchal translucency, 93 (39%) were chromosomally abnormal. Of the remaining 146 specimens, 80 CVS samples were chromosomally normal, had documentation of nuchal translucency > 3.0 mm, and were included in the study at the referring obstetrician's request. None of the 80 fetuses with an increased nuchal translucency and normal karyotype demonstrated a 22q11 microdeletion. By Fisher exact test, the probability of 80 fetuses with excess nuchal translucency having no deletions of chromosome 22 was not significantly different than the expected rate of 0.18% (P value = 1).

CONCLUSION

Routine 22q11 microdeletion analysis for fetuses with excess nuchal translucency is not indicated. Instead, we recommend storing an extra unbanded slide from the cultured CVS material to permit 22q11 FISH analysis should a cardiac malformation be identified later by fetal echocardiography.

Prenatal diagnosis ofde novo proximal interstitial deletion of 9q and review of the literature of uncommon aneuploidies associated with increased nuchal translucency

OBJECTIVES

To present the prenatal diagnosis and molecular cytogenetic analysis of de novo proximal interstitial deletion of 9q and to review the literature of uncommon aneuploidies associated with increased nuchal translucency (NT).

CASE

Obstetric ultrasound at 11 weeks' gestation revealed an increased NT thickness of 6.6 mm in a 31-year-old primigravid woman. At 13 weeks' gestation, repeat ultrasound examinations revealed a normal NT thickness of 1.8 mm. The subcutaneous nuchal fluid accumulation was no longer present at the following ultrasound scans. An amniocentesis was performed at 18 weeks' gestation.

RESULTS

Cytogenetic analysis revealed a karyotype of 46,XX,del(9)(q21.1q22.2). The parental karyotypes were normal. At 21 weeks' gestation, a 442-g female fetus was delivered with low-set ears, hypertelorism, and a thick nuchal fold. The parental origin of the interstitial deletion of 9q was analyzed with polymorphic DNA markers. With the microsatellite markers D9S238 (9q13), D9S889 (9q21.11), and D9S253 (9q22.2), two alleles inherited from the parents were seen in the proband, but with markers D9S1780 (9q21.31), D9S303 (9q21.32), D9S252 (9q21.33), and D9S316 (9q22.1), only one maternal allele was present. The deletion was of paternal origin.

CONCLUSIONS

Fetuses with uncommon aneuploidies may manifest increased NT in the first trimester. The present case provides evidence for a correlation between increased NT and interstitial 9q deletion. Prenatal identification of increased NT should alert subtle structural chromosome aberrations and prompt high-resolution karyotyping.

Prenatal diagnosis of 22q11 microdeletion in an early second-trimester fetus with conotruncal anomaly presenting with increased nuchal translucency and bilateral intracardiac echogenic foci

We report on a 16-week fetus, in which detection of increased nuchal translucency thickness and bilateral intracardiac echogenic foci led to the prenatal diagnosis of truncus arteriosus communis, interruption of the aortic arch and aplastic thymus. Cytogenetic examination confirmed a 22q11.2 microdeletion consistent with the suspected CATCH 22 syndrome. Subsequently hydrops fetalis developed and the fetus died in utero at 18 weeks. This case report supports the hypothesis that both cardiac failure and left ventricular outflow tract obstruction may cause increased nuchal translucency thickness. The association between increased nuchal translucency thickness and CATCH 22 syndrome should be considered in diagnostic procedures. The sonographic diagnosis of both increased nuchal translucency thickness and intracardiac echogenic foci requires specialist ultrasonography and echocardiography. In particular, identification of right-sided or bilateral echogenic foci should prompt further detailed examination.