The trisomy 18 syndrome

Perinatal management of trisomy 18: a survey of obstetricians in Australia, New Zealand and the UK

OBJECTIVE

The objective of this study was to explore the attitudes of obstetricians in Australia, New Zealand and the UK towards prenatally diagnosed trisomy 18 (T18).

METHOD

Obstetricians were contacted by email and invited to participate in an anonymous electronic survey.

RESULTS

Survey responses were obtained from 1018/3717 (27%) practicing obstetricians/gynaecologists. Most (60%) had managed a case of T18 in the last 2 years. Eighty-five per cent believed that T18 was a 'lethal malformation', although 38% expected at least half of liveborn infants to survive for more than 1 week. Twenty-one per cent indicated that a vegetative existence was the best developmental outcome for surviving children. In a case of antenatally diagnosed T18, 95% of obstetricians would provide a mother with the option of termination. If requested, 99% would provide maternal-focused obstetric care (aimed at maternal wellbeing rather than fetal survival), whereas 80% would provide fetal-oriented obstetric care (to maximise fetal survival). Twenty-eight per cent would never discuss the option of caesarean; 21% would always discuss this option. Management options, attitudes and knowledge of T18 were associated with location, practice type, gender and religion of obstetricians.

CONCLUSION

There is variability in obstetricians' attitudes towards T18, with significant implications for management of affected pregnancies.

Trisomy 18 syndrome: Towards a balanced approach

Trisomy 18 is a relatively common autosomal trisomy syndrome. It is due to either full or partial presence of an extra copy of chromosome 18. Its prevalence correlates positively with advanced maternal age. Affected infants usually exhibit a variable pattern of anomalies including growth restriction, marked psychomotor and cognitive disability and an array of physical findings including characteristic craniofacial features, clenched fists with overriding fingers, small fingernails, underdeveloped thumbs, short sternum and heart and kidney anomalies. The majority of these infants die within the first year of life; only 5% to 10% of them survive longer. Their death is primarily due to cardio-respiratory failure. In this case report of trisomy 18 we tried to highlight the importance of antenatal diagnosis and to emphasize the need for proper counseling at different points of time starting from the moment the condition is suspected until the point when diagnosis is confirmed and thereafter.

Chromosomal and multifactorial genetic disorders with oral manifestations

The chromosomal disorders are individually rare, but collectively they are common whereas the multifactorial disorders are the most common form of genetic disorders. The chromosomal anomalies typically arise from alterations in the DNA containing chromosomal regions and can be reliably detected by karyotype analysis, whereas the multifactorial disorders demonstrate multi-gene as well as environmental interactions. Both the chromosomal and multifactorial disorders may manifest signs and symptoms such as a combination of birth defects, physical disabilities, challenging behavior and certain craniofacial defects as well, the knowledge of which can aid in a better patient management in everyday practice of dentistry.

Isolated Asymptomatic Short Sternum in a Healthy Young Girl

Congenital sternal defects are rare deformities frequently associated with other anomalies of the chest wall and other organ systems. Although pectus excavatum, pectus carinatum, and cleft sternum can present as isolated deformity, in most cases they are associated with heart and inner organs anomalies and described as symptoms of syndromes like Marfan syndrome, Noonan syndrome, Poland anomaly, and Cantrell pentalogy. In contrast, the etiology of an isolated defect is not well understood. We observed a short sternum (dysmorphic manubrium, hypoplastic body, and complete absence of the xiphoid process) in a completely asymptomatic 13-year-old woman. A comprehensive instrumental exams panel was performed to exclude associated anomalies of the heart and of the other organ systems. The patient was completely asymptomatic and she did not need any medical or surgical treatment. To our knowledge, this is the first case of isolated short sternum reported in literature.

The natural history of pregnancies with a diagnosis of trisomy 18 or trisomy 13; a retrospective case series

BACKGROUND

Trisomy 18 (T18) and trisomy 13 (T13) are the second and third commonest autosomal aneuploidy syndromes respectively. While specific aspects of affected pregnancies have been documented in the literature, few studies document the overall natural history of the trisomies. This study aimed to examine the natural history (including diagnosis, pregnancy outcome, complications and survival) of T18 and T13 pregnancies in a setting where termination of pregnancy for fetal abnormality is not available.

METHODS

Cases were identified using birth registers, labour ward records, annual reports, medical records, ultrasound reports and reports from prenatal genetic testing. All identified T18 and T13 pregnancies in the study region from 2001 to 2012 were included. Individual chart reviews were performed for each case. Data were analysed using SPSS Version 20.

RESULTS

Forty-six T18 and twenty-four T13 pregnancies were identified. Most T18 cases (65%) were diagnosed prenatally, while only one third (33%) of T13 cases were prenatally diagnosed. Only three T18 pregnancies and one T13 pregnancy were electively terminated. A proportion of undiagnosed infants were delivered by emergency caesarean section. 48% (T18) and 46% (T13) infants survived following birth, for a median of 1.5 days (T18) and 7 days (T13). One T13 infant is currently alive over one year of age.

CONCLUSIONS

This large series provides information for professionals and women regarding the natural histories of trisomies 18 and 13. These pregnancies can go undiagnosed antenatally without routine anomaly scanning. While many fetuses die in-utero, postnatal survival is possible.

Non-invasive prenatal testing of trisomy 18 by an epigenetic marker in first trimester maternal plasma

Background

Quantification of cell-free fetal DNA by methylation-based DNA discrimination has been used in non-invasive prenatal testing of fetal chromosomal aneuploidy. The maspin (Serpin peptidase inhibitor, clade B (ovalbumin), member 5; SERPINB5) gene, located on chromosome 18q21.33, is hypomethylated in the placenta and completely methylated in maternal blood cells. The objective of this study was to evaluate the accuracy of non-invasive detection of fetal trisomy 18 using the unmethylated-maspin (U-maspin) gene as a cell-free fetal DNA marker and the methylated-maspin (M-maspin) gene as a cell-free total DNA marker in the first trimester of pregnancy.

Methodology/Principal Findings

A nested case-control study was conducted using maternal plasma collected from 66 pregnant women, 11 carrying fetuses with trisomy 18 and 55 carrying normal fetuses. Median U-maspin concentrations were significantly elevated in women with trisomy 18 fetuses compared with controls (27.2 vs. 6.7 copies/mL; P<0.001). Median M-maspin concentrations were also significantly higher in women with trisomy 18 fetuses than in controls (96.9 vs. 19.5 copies/mL, P<0.001). The specificities of U-maspin and M-maspin concentrations for non-invasive fetal trisomy 18 detection were 96.4% and 74.5%, respectively, with a sensitivity of 90.9%.

Conclusions

Our results suggest that U-maspin and M-maspin concentrations may be useful as potential biomarkers for non-invasive detection of fetal trisomy 18 in the first trimester of pregnancy, irrespective of the sex and genetic variations of the fetus.

Sonographic markers for early diagnosis of fetal malformations

Fetal malformations are very frequent in industrialized countries. Although advanced maternal age may affect pregnancy outcome adversely, 80%-90% of fetal malformations occur in the absence of a specific risk factor for parents. The only effective approach for prenatal screening is currently represented by an ultrasound scan. However, ultrasound methods present two important limitations: the substantial absence of quantitative parameters and the dependence on the sonographer experience. In recent years, together with the improvement in transducer technology, quantitative and objective sonographic markers highly predictive of fetal malformations have been developed. These markers can be detected at early gestation (11-14 wk) and generally are not pathological in themselves but have an increased incidence in abnormal fetuses. Thus, prenatal ultrasonography during the second trimester of gestation provides a “genetic sonogram”, including, for instance, nuchal translucency, short humeral length, echogenic bowel, echogenic intracardiac focus and choroid plexus cyst, that is used to identify morphological features of fetal Down’s syndrome with a potential sensitivity of more than 90%. Other specific and sensitive markers can be seen in the case of cardiac defects and skeletal anomalies. In the future, sonographic markers could limit even more the use of invasive and dangerous techniques of prenatal diagnosis (amniocentesis, etc.).