Prenatal detection of fetal trisomy 18 through abnormal sonographic features

Trisomy 18-when the diagnosis is compatible with life

Trisomy 18 is an autosomal chromosomal disorder characterized by the presence of an extra 18 chromosome. In the last decades, and as novel therapeutic options emerged, a paradigm shift on the treatments available to these children occurred, establishing the need to deepen the knowledge regarding the management/treatment of children diagnosed with trisomy 18. This retrospective cohort study sought to characterize the clinical path and survival of the children with the diagnosis of trisomy 18 followed in a tertiary pediatric hospital between 1995 and 2020. Medical records were reviewed, and epidemiological and clinical features and follow-up data were collected. Six patients were identified, two with mosaicism (33.3%) and four were female (66.7%). All had cardiovascular, cognitive, and physical development anomalies or minor congenital anomalies. Most presented neurological anomalies (n = 4, 66.7%) and feeding difficulties (n = 4, 66.7%). Four children (66.7%) required medical devices or equipment and all required chronic medication. Two children (33.3%) underwent surgical interventions. Four children (66.7%) were hospitalized in the last year of life. Three patients had a do not resuscitate order (50%) but only one child was referred to a pediatric palliative care team (16.7%). One-month, 1-year, and 10-year survival were 66.7% (n = 4), 33.3% (n = 2, both with mosaicism), and 16.7% (n = 1, with mosaicism) respectively.

CONCLUSIONS

Knowledge of the multiple comorbidities and complex care needs of children with this syndrome is crucial. Every-day care and decisions about invasive treatments may raise ethical issues. Early referral to pediatric palliative care teams is essential to promote a holistic advanced care plan for both the patient and his family.

WHAT IS KNOWN

• The increase in survival and the high morbimortality that trisomy 18 still entails demands a careful deliberation on the use of invasive treatment.

WHAT IS NEW

• Recent studies show that the labels of "incompatible with life"/"lethal" are not adequate, establishing a need to change this mindset. • The development of pediatric palliative care teams in the last decade and early referral allow for an optimal individualized advanced care plan. Under-referral to pediatric palliative care teams persists and efforts must be made to increase awareness of their existence and role in patient care.

Non-invasive prenatal testing in mitigating concerns from invasive prenatal diagnostic testing: retrospective assessment of utility in an academic healthcare system in the US

OBJECTIVE

Non-invasive prenatal testing (NIPT) is a front-line screening for fatal chromosomal aneuploidy. In pregnant women with a risk of having fetal congenital disorders, NIPT is anticipated to reduce the needs of invasive prenatal diagnostic test (IPD). The objective of this study was to understand the acceptance of NIPT and the utility of NIPT to mitigate concerns about IPD in the US high-risk pregnancy management.

DESIGN AND SETTING

This was a retrospective observational research using healthcare records obtained from an academic healthcare system in the US. The study consisted of site-level longitudinal analysis and patient-level cross-sectional analysis.

PARTICIPANT

A total of 5660 new high-risk pregnancies with age ≥35 years were identified for the longitudinal trend analysis. Cross-sectional utility assessment included 2057 pregnant women.

EXPOSURE AND OUTCOME MEASURES

Longitudinal trends of NIPT order, IPD procedure and the number of patients diagnosed with high-risk pregnancy were descriptively summarised. In the cross-sectional assessment, we tested the association between the use of NIPT and IPD using multivariable regression.

RESULTS

The rate of increase in the NIPT use exceeded the changes in the number of high-risk pregnancies with age ≥35 years, while the number of annual IPD procedures has fluctuated without specific trends. There was no significant association between the numbers of NIPT and IPD with the adjusted ORs between 0.90 and 1.14 (p>0.1). The order of NIPT was not selected as an independent variable predicting the use of IPD. Clinical characteristics indicating low socioeconomic status and limited healthcare coverage are associated with less use of NIPT and lower clinical utility.

CONCLUSION

Although prenatal care accepted NIPT over the last decade, the utility of NIPT in mitigating concerns on IPD is unclear and needs further investigation. Limited clinical utility should be addressed in the context of disparity in prenatal care.

A rare case report of Edwards syndrome with immature teratoma in submandibular region and literature review

Trisomy 18 (Edward syndrome) was first described by Edwards et al. in 1960. The condition is the second most common autosomal trisomy syndrome in males. The prevalence in infants is estimated as 1/6000-1/8000. Those affected have a high mortality rate – only 4% may survive their first year.

The study illustrates the first reported case of Edwards syndrome with immature teratoma in submandibular region.

A 33-year-old multigravida had a normal antenatal course until 36 weeks of gestation. Two hours after delivery, the baby was transported to a neonatal ward, where several malformations were described: a tumour formation the size of a walnut in the right submandibular region, ear abnormality, micrognathia with high arched palate, overlapping fingers, and feet deformities. A genetic test was performed which confirmed trisomy 18. After 26 days of assisted ventilation and oxygen therapy, the newborn developed hyaline-membrane disease, dilatation of the pulmonary artery and the right side of the heart, thrombosis of the right atrium and these conditions were determined to be the cause of death.

The autopsy and histological examination confirmed the aforementioned malformations finding also a kidney with duplicated collecting system on the right and ectopic ureter in the left kidney. The submandibular tumour was determined to be immature teratoma.

Conclusion: This is the first presented case in the literature of a newborn with Edwards syndrome combined with immature teratoma.

Importance of Follow-Up and Early Detailed Evaluation in Early Onset Growth Restricted Fetuses

Early onset fetal growth restriction (EO-FGR) is associated with significant feto-maternal complications, therefore efforts should be made to identify the causes and the potential outcome of the pregnancy. Some of the pitfalls in first-trimester imaging of the fetal anomalies are related to the inadequacy of the examination, because of the fetal position and limited clarity in relation to the size of the structures being examined. In this paper we present a case where careful ultrasound scan follow-up and the use of both approaches transabdominal and transvaginal were useful to complete a detailed structural evaluation as part of the diagnosis, management and prognosis of a fetuses diagnosed with EO-FGR in the first trimester and a triploidy with atypical ultrasound features.

Sensitivity of prenatal ultrasound for detection of trisomy 18

Objectives: To evaluate the sensitivity of prenatal ultrasound (US) for trisomy (T18) diagnosis and describe US findings in a large tertiary care institution in the USA. Materials and methods: This was a retrospective cohort of all T18 cases diagnosed at our institution from October 2004 to October 2014 based on prenatal or postnatal genetic diagnostic testing. We included all women with a fetus affected by T18 who had a comprehensive US by a maternal-fetal medicine specialist performed at our institution. US findings were reviewed, classified by organ system, and categorized as an anomaly or soft marker. Chi-square or t-test was used for statistical analysis. Results: We included 128 cases of T18 with confirmed cytogenetic analysis -110 (86%) of which were diagnosed prenatally or suspected by cell-free DNA and confirmed postnatally, and 18 of which underwent neonatal blood sampling alone. One hundred and twenty-one (95%) had at least one abnormal US finding. Anomalies were more frequently identified on US at ≥20 weeks as compared with <20 weeks (93% versus 76%; p = .004). The mean number of findings detected per fetus was 5.1 ± 3.0. Fetuses diagnosed by postnatal sampling alone had a similar number of US exams performed and number of abnormal findings compared to those diagnosed prenatally. Conclusion: Ninety-five percent of fetuses with T18 had at least one abnormal US finding. This sensitivity of is higher than reported in most prior studies, but is not 100%, and should be considered when counseling women regarding prenatal diagnosis of T18. Rationale: Historical detection rates for abnormal sonographic findings in trisomy 18 fetuses range from 70% to 100%. These studies are limited by small sample sizes. This is a contemporary study of ultrasound findings in a large group of women with confirmed trisomy 18 by prenatal or postnatal genetic diagnosis. We provide expansive detail on soft markers and anomalies broken down by organ-system and gestational age.

Intrauterine death in singleton pregnancies with trisomy 21, 18, 13 and monosomy X

Summary A retrospective study from November 2004 to May 2012, conducted at the Obstetric Clinic of Hospital das Clínicas, Faculdade de Medicina, Universidade de São Paulo (HC-FMUSP), which included 92 singleton pregnancies with prenatal diagnosis of trisomy of chromosome 21 (T21), 18, 13 (T13/18) and monosomy X (45X), with diagnosis performed until the 26th week of pregnancy. The aim of the study was to describe the frequency and to investigate predictors of spontaneous fetal death (FD). Diagnosis (T21, n=36; T13/18, n=25; 45X, n=31) was made at a mean gestational age of 18.3±3.7 weeks, through chorionic villus biopsy (n=22,24%), amniocentesis (n=66, 72%) and cordocentesis (n=4, 4%). Major malformations were present in 45 (49%); with hydrops in 32 (35%) fetuses, more frequently in 45X [n=24/31, 77% vs. T21 (n=6/36, 17%) and T13/18 (n=2/25, 8%), p<0.001]. Specialized fetal echocardiography was performed in 60% (55/92). Of these, 60% (33/55) showed changes in heart morphology and/or function. Fetuses with T13/18 had a higher incidence of cardiac anomalies [60 vs. 25% (T21) and 29% (45X), p= 0.01]. FD occurred in 55 (60%) gestations, being more frequent in 45X [n=26/31, 84% vs. T21 (n=13/36, 36%) and T13/18 (n=16/25, 64%), p<0.01]. Stepwise analysis showed a correlation between hydrops and death in fetuses with T21 (LR= 4.29; 95CI=1.9-8.0, p<0.0001). In fetuses with 45X, the presence of echocardiographic abnormalities was associated with lower risk of FD (LR= 0.56; 95CI=0.27- 0.85, p=0.005). No predictive factors were identified in the T13/18 group. Intra- uterine lethality of aneuploid fetuses is high. Occurrence of hydrops increases risk of FD in pregnancies with T21. In pregnancies with 45X, the occurrence of echocardiographic changes reduces this risk.

Retrospective cohort of trisomy 18 (Edwards syndrome) in southern Brazil

CONTEXT AND OBJECTIVE

Trisomy 18 (T18), or Edwards syndrome, is a chromosomal disease characterized by a broad clinical picture and a poor prognosis. Our aim was to describe clinical, radiological and survival data of a cohort of patients prenatally diagnosed with T18.

DESIGN AND SETTING

Retrospective single cohort in the Fetal Medicine Service of Hospital Materno Infantil Presidente Vargas (HMIPV).

METHODS

All sequential patients with T18 registered at the Fetal Medicine Service of HMIPV between January 2005 and September 2013 were considered. We gathered their clinical, radiological and survival data and used the Kaplan-Meier test for survival analysis.

RESULTS

Ten patients were diagnosed with T18, of whom seven (70%) were female. The majority (90%) were referred due to malformations seen on ultrasound. The mean gestational age at the first evaluation was 25.5 weeks. At karyotyping, the defects were considered multiple in only four patients (40%). All the fetuses presented full trisomy of chromosome 18. The main abnormality observed was congenital heart disease (n = 7). Intrauterine death occurred in half of the patients (50%). All live patients (n = 5) were born through cesarean section presenting low weight and low Apgar scores. The median length of survival after birth was 18 days.

CONCLUSIONS

T18 is associated with a high risk of fetal and neonatal death. The majority of the patients present major malformations identified through ultrasound, such as congenital heart defects, which could help in identifying such cases prenatally.

Facial profile markers in second- and third-trimester fetuses with trisomy 18

OBJECTIVES

To evaluate nasal bone length (NBL), maxilla-nasion-mandible (MNM) angle, fetal profile (FP) line, prenasal thickness (PT), prenasal thickness to nasal bone length (PT:NBL) ratio and prefrontal space ratio (PFSR) as markers of trisomy 18 in the second and third trimesters of pregnancy.

METHODS

The NBL, MNM angle, FP line, PT, PT:NBL ratio and PFSR were measured retrospectively from stored two-dimensional images or three-dimensional volumes of trisomy-18 fetuses, and were compared with our previously reported normal ranges for euploid fetuses. Additional ultrasound findings were noted at initial routine second-trimester scan and at subsequent advanced ultrasound examination performed after referral for karyotyping.

RESULTS

A total of 43 trisomy-18 fetuses were included in the analysis. At initial examination, median gestational age was 21 + 2 weeks. NBL and PT were correlated with gestational age (P < 0.001), but the other markers were not. Mean NBL, MNM angle, PT, PT:NBL ratio and PFSR were 3.76 mm, 16.67°, 4.25 mm, 1.39 and 0.87, respectively. The FP line was zero (normal) in 53.7% of cases and negative (abnormal) in 46.3%. All markers were significantly associated with trisomy 18, with the PT:NBL ratio yielding the highest detection rate (88.4%) followed by NBL (83.7%), MNM angle (56.4%), FP line (46.3%), PT (27.9%) and the PFSR (20.5%) (for a 5% false-positive rate for the continuous variables). Various combinations of the four best markers (NBL, FP line, MNM angle and PT:NBL ratio) yielded detection rates of between 72% and 95%. Structural anomalies were not detected in 22% of fetuses at the initial scan and in 2% at the advanced scan.

CONCLUSIONS

The PT:NBL ratio and NBL are robust second- and third-trimester markers for trisomy 18. A negative FP line has a 0% false-positive rate and the potential to differentiate between trisomy 18 and Down syndrome, as in the latter the FP line is often positive. No major anomaly was observed at the initial scan in about a quarter of trisomy-18 fetuses, underlining the role of second-trimester facial marker evaluation.

Prenatal diagnosis of craniomaxillofacial malformations: a characterization of phenotypes in trisomies 13, 18, and 21 by ultrasound and pathology

OBJECTIVE

To determine the relationship between trisomies 13, 18, and 21 and craniofacial malformations detected by prenatal sonography.

DESIGN

During a 29-year period (1976 through 2004), prenatal sonographic findings of 69 fetuses with trisomy 13; 171 fetuses with trisomy 18; 302 fetuses with trisomy 21; and 17 fetuses with other trisomies were evaluated retrospectively, after fetal karyotype identification. Sonographic findings were compared with autopsy results in 209 patients (trisomy 13, n=39; trisomy 18, n=64; and trisomy 21, n=106).

RESULTS

For trisomy 13, cleft deformities were detected prenatally in 65.2%, and of the 39 cases with pathological information, 76.9% were found to have a cleft deformity. Ocular and orbital abnormalities were found in 28%. Malformations of the jaws and abnormal profiles were more frequently diagnosed postnatally than prenatally. For trisomy 18, abnormal profiles (41.5%) and ear abnormalities (5.3%) were the most noticeable ultrasound markers, next to abnormalities of the neurocranium (36.8%) and cranial bone configuration (21.6%). Dysmorphisms of the eye, ear, or nose were detected more frequently in autopsy cases. For trisomy 21, ultrasound showed an aberrant shape of the skull in 14.2% of fetuses. In general, the ocular-orbital and nasal abnormalities in fetuses with trisomy 18 or 21 were more evident in pathological examination than in prenatal ultrasound imaging.

CONCLUSIONS

Facial anomalies are common in the major trisomies, and their prenatal sonographic identification should be improved. The above-mentioned facial anomalies provide sufficient reason to consider performing cytogenic evaluation.

Prenatal diagnosis of craniomaxillofacial malformations: a characterization of phenotypes in trisomies 13, 18, and 21 by ultrasound and pathology

OBJECTIVE

To determine the relationship between trisomies 13, 18, and 21 and craniofacial malformations detected by prenatal sonography.

DESIGN

During a 29-year period (1976 through 2004), prenatal sonographic findings of 69 fetuses with trisomy 13; 171 fetuses with trisomy 18; 302 fetuses with trisomy 21; and 17 fetuses with other trisomies were evaluated retrospectively, after fetal karyotype identification. Sonographic findings were compared with autopsy results in 209 patients (trisomy 13, n=39; trisomy 18, n=64; and trisomy 21, n=106).

RESULTS

For trisomy 13, cleft deformities were detected prenatally in 65.2%, and of the 39 cases with pathological information, 76.9% were found to have a cleft deformity. Ocular and orbital abnormalities were found in 28%. Malformations of the jaws and abnormal profiles were more frequently diagnosed postnatally than prenatally. For trisomy 18, abnormal profiles (41.5%) and ear abnormalities (5.3%) were the most noticeable ultrasound markers, next to abnormalities of the neurocranium (36.8%) and cranial bone configuration (21.6%). Dysmorphisms of the eye, ear, or nose were detected more frequently in autopsy cases. For trisomy 21, ultrasound showed an aberrant shape of the skull in 14.2% of fetuses. In general, the ocular-orbital and nasal abnormalities in fetuses with trisomy 18 or 21 were more evident in pathological examination than in prenatal ultrasound imaging.

CONCLUSIONS

Facial anomalies are common in the major trisomies, and their prenatal sonographic identification should be improved. The above-mentioned facial anomalies provide sufficient reason to consider performing cytogenic evaluation.

HDlive imaging of the face of fetuses with autosomal trisomies

BACKGROUND

Our objective is to present our experience of facial dysmorphism reconstructed employing conventional three-dimensional (3D) ultrasound and HDlive in fetuses with autosomal trisomies.

METHODS

Seven fetuses with autosomal trisomies (one case of trisomy 13, three of trisomy 18, and three of trisomy 21) at 16-38 weeks' gestation were studied using 3D ultrasound and HDlive.

RESULTS

In one case of trisomy 21 at 29 weeks and 5 days, upward slanting eyes, a flattened nose, low-set ears, and the corners of the mouth turned down were noted employing HDlive. In the other two cases of trisomy 21, both techniques showed the same facial findings. In one case of trisomy 18 at 27 weeks and 6 days, a small head accompanied by a prominent back portion of the head, low-set ears, a small jaw, upturned nose, narrow eyelid folds, and widely spaced eyes were identified using HDlive. In the other two cases of trisomy 18, HDlive showed more detailed features of the fetal face compared to conventional 3D ultrasound. In the single case of trisomy 13 at 31 weeks and 1 day, cleft lip and close-set eyes were recognized with both 3D ultrasound and HDlive.

CONCLUSION

HDlive can provide clearer facial images than conventional 3D ultrasound. In particular, HDlive is superior to conventional 3D ultrasound for the depiction of eye fissures because of its shadowing effect. HDlive may be a useful diagnostic modality for the antenatal evaluation of subtle fetal facial dysmorphism.

The role of ultrasound in the diagnosis of fetal genetic syndromes

The use of ultrasound in the prenatal diagnosis of fetal genetic syndromes is rapidly evolving. Advancing technology and new research findings are aiding in the increased accuracy of ultrasound-based diagnosis in combination with other methods of non-invasive and invasive fetal testing. Ultrasound as a screening tool for aneuploidy and other anomalies is increasingly being used throughout pregnancy, beginning in the first trimester. Given the number of recorded syndromes, it is important to identify patterns and establish a strategy for identifying abnormalities on ultrasound. These syndromes encompass a wide range of causes from viral, substance-linked, chromosomal, and other genetic syndromes. Despite the ability of those experienced in ultrasound, it is important to note that not all fetal genetic syndromes can be identified prenatally, and even common syndromes often have no associated ultrasound findings. Here, we review the role of ultrasound in the diagnosis of fetal genetic syndromes.

Prenatal diagnosis of i(18q) and dup(18q) cases by quantitative fluorescent PCR

Particular sonographic fetal malformations are common in chromosome 18 aberrations, requiring invasive prenatal tests to confirm the diagnosis. Karyotyping is the gold standard assay in these cases, although it is a high complexity, expensive and approximately 2 weeks turnaround time test. On the contrary, quantitative fluorescent PCR is considered an accurate, simple, low cost and rapid assay, particularly useful for the diagnosis of aneuploidies of chromosomes 13, 18 and 21 and for the detection of maternal cell contamination of the sample. Clinical presentation of two cases of rare chromosome 18 defects, diagnosed using both techniques. One case was an isochromosome and the other was a partial duplication. Quantitative fluorescent PCR was an invaluable tool for the cytogenetics laboratory.

Imaging clues in the prenatal diagnosis of syndromes and aneuploidy

Advances in fetal sonography and MRI have increased both the range and diagnostic accuracy of detectable fetal anomalies, with many anomalies detectable earlier in pregnancy. The presence of structural anomalies greatly raises the risk that the fetus has a syndrome or abnormal karyotype. In addition, new techniques in maternal serum screening have greatly increased the ability to identify pregnant patients at risk for anomalies and syndromes. This paper reviews maternal first- and second-trimester serum screening and imaging and covers many of the most common fetal karyotypic and structural anomalies.

Pränatale Detektion fetaler chromosomaler Aberrationen im 1. und 2. Trimenon

Die modernen nichtinvasiven Verfahren der pränatalen Medizin, vertreten vor allem durch das Ersttrimesterscreening, ermöglichen eine frühe Risikoeinschätzung bzgl. der häufigsten Aneuploidien. Durch die flächendeckende Anwendung dieser Methode mit derzeit weit über 4000 zertifizierten Gynäkologen bundesweit stellt dies heute einen weit verbreiteten Standard dar. Die klassische „genetische“ Sonographie, d. h. die Detektierung von Softmarkern als Hinweiszeichen für eine Aneuploidie im 2. Trimenon, hat an Bedeutung verloren. Allerdings ist der Fehlbildungsultraschall im 2. Trimenon nach wie vor von sehr großer Bedeutung und stellt den „Goldstandard“ für die Entdeckung angeborener Fehlbildungen dar. Der Pränatalmediziner muss in der Lage sein, während dieser Untersuchung Softmarker zu erkennen, um ggf. eine Reevalution des mütterlichen Risikos bzgl. Aneuploidien vorzunehmen.

Persistent right umbilical vein: a prenatal condition worth mentioning?

OBJECTIVES

To investigate the incidence and clinical impact of prenatally diagnosed persistent right umbilical vein (PRUV) in a referral population and to evaluate the findings together with those from previous publications.

METHODS

This was a retrospective analysis of 39 cases with PRUV diagnosed in three tertiary referral centers for prenatal medicine between 1996 and 2009. Fetuses with situs inversus, situs ambiguous and heterotaxy (left and right isomerism) were excluded. During the study period 46 653 consecutive high- and low-risk pregnancies were examined. The prenatal sonograms and neonatal outcome data of affected individuals were reviewed. Our findings were analyzed together with findings retrieved from the scientific literature.

RESULTS

Twenty-nine fetuses had an isolated PRUV as a single anomaly, whereas 10/39 (25.6%) were found to have PRUV accompanied by additional minor and major abnormalities. These anomalies comprised mainly cardiovascular, genitourinary and gastrointestinal malformations. In common with our series, previously published cases of isolated PRUV (n = 197) displayed an uneventful course of pregnancy and a favorable postnatal outcome. Sixty-six previously reported cases of PRUV with additional anomalies were identified in the literature. Intrahepatic umbilical drainage is the most frequent type of PRUV. Including our cases, there were 16 cases (5.3%) with extrahepatic drainage of PRUV, all of which had additional anomalies.

CONCLUSIONS

Consistent with previous reports, in the majority of cases (74.8%) PRUV is an isolated finding. While these cases carry an excellent prognosis, PRUV can be associated with severe congenital anomalies, so this finding should prompt detailed prenatal assessment of the fetus.

First-trimester sonographic findings in trisomy 18: a review of 53 cases

OBJECTIVE

To report our experience with first-trimester sonographic findings in pregnancies complicated by trisomy 18.

METHODS

Proven cases of trisomy 18 undergoing sonographic examination between 11 + 0 and 13 + 6 weeks of gestation were retrospectively identified. Information on maternal demographics, prenatal sonographic findings, and chromosomal analysis results was obtained by reviewing the ultrasound reports and medical records.

RESULTS

During the 12-year period from July 1997 to June 2009, 53 cases of full trisomy 18 had first-trimester sonographic examination performed at our institution. All but one fetus displayed one or more abnormal sonographic finding, most commonly increased nuchal translucency thickness (n = 48, 91%). Absent or hypoplastic nasal bone was documented in 53% of the fetuses in which this marker was specifically looked for. Structural anomalies included omphalocele in 11 (21%), abnormal posturing of the hands in three (6%), megacystis in two (4%), and abnormal four-chamber view of the heart in two (4%). Early-onset fetal growth restriction and bradycardia were documented in 14 (26%) and 4 (8%) of the cases, respectively.

CONCLUSIONS

Our study demonstrates that a large number of fetuses with trisomy 18 have abnormal sonographic findings in the first trimester. However, the sonographic features usually found in the second-trimester are difficult to detect at an early gestational age. The recognition of the specific first-trimester sonographic pattern of trisomy 18 may allow improved detection of this serious condition in early pregnancy.

Second trimester prenatal ultrasound for the detection of pregnancies at increased risk of Trisomy 18 based on serum screening

OBJECTIVE

To describe ultrasound findings in fetuses with Trisomy 18.

METHODS

Prospective population-based cohort study of second trimester ultrasound among Californian women who were at increased risk of chromosome abnormality based on serum screening between November 1999 and April 2001. Structural anomalies plus the following soft markers were assessed: nuchal fold thickening, choroid plexus cyst (CPC), echogenic intracardiac focus, echogenic bowel, renal pyelectasis, clenched hands; clinodactyly; short femur, short humerus and a single umbilical artery (SUA).

RESULTS

Overall, 8763 women underwent ultrasound evaluation, including 56 whose fetuses had Trisomy 18. Ultrasound anomalies were seen in 89% of Trisomy 18 fetuses, as compared with 14% of normal fetuses. If the genetic sonogram was normal (no structural anomaly and no soft marker), the risk was reduced by approximately 90%. The ultrasound soft markers were typically seen in conjunction with structural anomalies in affected fetuses and in the absence of a structural anomaly, most isolated ultrasound soft markers were not associated with Trisomy 18. The only exception was an isolated CPC, seen as the only finding in 11% of fetuses with Trisomy 18.

CONCLUSIONS

If the genetic sonogram is used as a sequential test following serum biochemistry, a normal ultrasound study reduces the likelihood of Trisomy 18 substantially even if a woman has abnormal serum biochemistry. The presence of an isolated CPC raises the risk, but not high enough to prompt invasive testing.

Evaluating the incidence and likelihood ratios for chromosomal abnormalities in fetuses with common central nervous system malformations

OBJECTIVE

To determine the incidence and likelihood ratios for chromosomal abnormalities in fetuses with common central nervous system malformations on ultrasound.

STUDY DESIGN

A database derived retrospective cohort study of all patients referred for ultrasound and genetic evaluation from 1990-2006. Fetal karyotypes were delineated by prenatal diagnosis or postnatal examination. The incidence and likelihood ratios were calculated for the association of each central nervous system abnormality with trisomy 13, 18, and 21.

RESULTS

Of 62,111 women included, 587 (0.9%) had major fetal central nervous system abnormalities. The only central nervous system anomalies associated with trisomy 21 were ventriculomegaly and choroid plexus cysts. When isolated, only spina bifida, holoprosencephaly, and agenesis of the corpus callosum were significantly associated with trisomy 13, anencephaly with trisomy 18, and ventriculomegaly with trisomy 21. Likelihood ratios positive range from 2-20 depending on the central nervous system malformation and aneuploidy type.

CONCLUSION

Central nervous system malformations detected on ultrasound are strongly associated with and predictive of chromosomal abnormalities, especially trisomy 13 and 18.

Sonographic findings of trisomy 18 in the second trimester of pregnancy

OBJECTIVE

The purpose of this study was to examine the sonographic findings in fetuses with trisomy 18 in the second trimester of pregnancy.

METHODS

A retrospective review of the cytogenetic laboratory databases at 6 tertiary referral centers identified all cases of trisomy 18. The prenatal sonographic studies in fetuses at 15 to 21 weeks' gestation, done before invasive testing for the karyotype, were reviewed for anatomic and biometric findings. We defined abnormal fetal biometric findings as a biometric measurement (biparietal diameter, abdominal circumference, or femur length) below the fifth percentile in the second trimester.

RESULTS

Of 98 fetuses with trisomy 18, 95 (97%) were detected sonographically; an anomaly was found in 92 (94%). A biometric measurement below the fifth percentile was noted in 50 (51%). Cardiac (63%) and central nervous system (34%) anomalies were most frequently detected. Although choroid plexus cysts were commonly seen, no fetuses with trisomy 18 and isolated choroid plexus cysts were found.

CONCLUSIONS

Targeted sonography identified abnormal fetal anatomy or abnormal biometric findings in 97% of fetuses with trisomy 18 in the second trimester. A biometric measurement below the fifth percentile was noted in half of the cases in the second trimester.

Three- and 4-dimensional ultrasonography in the prenatal evaluation of fetal anomalies associated with trisomy 18

OBJECTIVE

The purpose of this study was to assess the usefulness of 3- and 4-dimensional ultrasonography (3D/4DUS) for the description of anomalies associated with trisomy 18 and to determine whether 3D/4DUS adds diagnostic information over what is provided by conventional 2-dimensional ultrasonography (2DUS) alone.

METHODS

Twenty-six fetuses subsequently proven to have trisomy 18 underwent prenatal ultrasonographic evaluations by both 2DUS and 3D/4DUS. Volume data sets were acquired by the same sonographers after the conventional 2DUS examinations and were explored with 4-dimensional imaging software by another independent examiner blinded to the indications of 2DUS. The findings detected by 2DUS and 3D/4DUS were compared with those acquired at autopsy. The sensitivity of each modality for detecting anomalies was calculated and compared by the McNemar test.

RESULTS

Excluding polyhydramnios, there were 131 anomalies confirmed postnatally in 26 fetuses with trisomy 18. There was a statistically significant difference in the sensitivity for detecting anomalies between 3D/4DUS and 2DUS (93.89% versus 73.28%; McNemar value = 23.31; P < .05), especially in anomalies of the face/neck (96.15% versus 65.38%; McNemar value = 6.13; P < .05) and extremities (96.3% versus 48.15%; McNemar value = 11.07; P < .05). Three- and 4-dimensional ultrasonography provided additional diagnostic information for 83.97% of the anomalies related to trisomy 18 and influenced the obstetric management of 4 fetuses.

CONCLUSIONS

Three- and 4-dimensional ultrasonography offered diagnostic advantages for many anomalies associated with trisomy 18, especially for anomalies of the extremities and face. This modality could be a powerful adjunct to 2DUS in the prenatal anatomic evaluation of fetuses with trisomy 18.

Identification and characterization of a new type of asymmetrical dicentric chromosome derived from a single maternal chromosome 18

Molecular cytogenetic analysis identified a new type of dicentric chromosome involving different breakpoints at 18q in a female fetus. The chromosome anomaly was designated as an asymmetrical pseudoisodicentric chromosome 18, 46,XX,psu dic(18)(pter-->q11.2::q21.3-->pter)mat. A series of BAC clones for 18q11.2 and q21.3 regions were used to identify one breakpoint within the region q11.2 between 19.8 and 21.6 Mb from the telomere of 18p and another breakpoint within q21.3 between 55.4 and 56.9 Mb from the telomere of 18p by FISH analysis. Real-time quantitative PCR and microsatellite analysis further verified that the dicentric chromosome was maternal in origin and resulted from a break-reunion between sister chromatids of a single maternal chromosome. We propose that a loop-type configuration of sister chromatids took place and that the break-reunion occurred at cross sites of the loop to form an asymmetrical isodicentric chromosome during either mitosis or meiosis. In this case, the asymmetrical pseudoisodicentric resulted in an 18pter--> q11.2 duplication and an 18q21.3-->qter deletion, which could have led to certain dysmorphic features of 18q- syndrome in this fetus.

Management options for echogenic intracardiac focus and choroid plexus cysts: A review including Australian Association of Obstetrical and Gynaecological Ultrasonologists consensus statement

Echogenic intracardiac focus and choroid plexus cysts are common findings at the midtrimester ultrasound. These findings have been linked with an increased risk of Down syndrome and trisomy 18. Most fetuses with these findings will, however, not have chromosomal abnormalities, especially when these findings are isolated. Patients experience considerable anxiety when informed of these findings and require extensive counselling in order to minimize anxiety not only about aneuploidy but also about the structure and development of the heart and brain. Although early studies showed an association with aneuploidies, several recent studies have cast doubt on this association. Many of the early studies were carried out in high-risk populations or in populations that had not had the benefit of other screening tests. Many Australian and New Zealand patients will access screening tests designed to detect these aneuploidies before presenting for a midtrimester ultrasound. Patients who have been screened by nuchal translucency, maternal serum screening or some combination of the two will already have had most cases of Down syndrome and trisomy 18 detected, and any soft marker found will almost certainly be a false positive. It is time to rethink the management of these markers. Recent evidence indicates that if these markers are found in isolation in an otherwise low-risk pregnancy, then there is minimal or no increase in the risk of Down syndrome or trisomy 18: these markers should be considered normal variants. The Australian Association of Obstetrical and Gynaecological Ultrasonologists consensus statement on these markers is included.

Comparison of First and Second Trimester Aneuploidy Risk Assessment

Counseling regarding the options for aneuploidy risk assessment is complicated and requires thorough counseling with the patient. Second trimester serum risk assessment has been the gold standard because of widespread availability, low cost, and vast experience with counseling and performance. First trimester risk assessment is becoming more widely available and provides increased sensitivity for Down syndrome detection with a detection rate of approximately 87% (95% confidence interval: 84.0% to 89.4%), at a fixed false-positive rate of 5%. With the advent of first trimester techniques, controversy has arisen as there are advocates for the different recently available approaches. In this chapter, we outline the various options in a manner that will provide practical information for physicians offering such testing. Clearly, implementation of first trimester risk assessment requires special training and meticulous quality control standards for nuchal translucency and laboratory measurements, access to chorionic villus sampling, and also appropriate counseling regarding risk assessment options.

The second trimester genetic sonogram

The genetic sonogram, a fetal anatomic survey targeted at identifying features associated with aneuploidy, is carried out between 15 and 20 weeks' gestation. It has evolved as an adjunctive screening tool capable of further refining the individualized risk-calculation for trisomy that is based on maternal age or serum screening markers. The significance of a range of major structural anomalies and so-called "soft-markers" for trisomy, detected both in isolation and in combination, has been widely investigated. This review serves to describe the key components of the second trimester genetic sonogram and to illustrate how these markers are integrated into risk assessment for aneuploidy.

Trisomy 18: Fetal ultrasound findings at different gestational ages

The aim of this article is evaluate the sonograhic findings in fetuses with trisomy 18 at different gestational ages. The cases were recruited from pregnant women, who underwent to prenatal diagnosis in the period from October 1995 to September 2006. Seventy-one fetuses with trisomy 18 were diagnosed. On review of the sonograms the majority of these cases had ultrasound anomalies (sensitivity of 91.5%). The most frequent anomalies were abnormalities of extremities (40.8%) and fetal growth restriction (35.2%). More frequently (54.9%) two or more anomalies were present. Nearly all fetuses with trisomy 18 had sonographic abnormalities. Likely improved high-resolution equipment and attention to details by skilled operators led to the detection of most anomalies to trisomy 18. Knowledge of types of specific ultrasound findings can improve prenatal diagnosis in order to provide invasive procedures only when indicated, and to avoid amniocentesis when ultrasound signs are not observed in women at high risk from positive biochemical testing.

Trisomy of chromosome 18 in the baboon (Papio hamadryas anubis)

Trisomy 18 is usually a lethal chromosomal abnormality and is the second most common autosomal trisomy in humans, with an incidence of 1:8000 live births. It is commonly associated with abnormalities of the lower and upper extremities, having the frequency of 95% and 65%, respectively. A newborn female olive baboon (Papio hamadryas anubis) was diagnosed with intrauterine growth retardation and severe arthrogryposis-like congenital joint deformities. Cytogenetic analysis including G-banding and fluorescence in situ hybridization (FISH) revealed that the congenital abnormalities were associated with chromosomal mosaicism for trisomy 18. Genetic analysis with microsatellites from chromosome 18 confirmed the maternal origin of the extra chromosome 18. This is the first report of trisomy 18 in the baboon, which may be a promising animal model of human disease.

Ectopia cordis in a fetus with trisomy 18

Trisomy 18 is the second-most common autosomal trisomy and represents one third of the chromosomal trisomies identified prenatally. We present a case of a fetus with trisomy 18 in which thoracoabdominal ectopia cordis was detected prenatally; it was noted as a dominant defect on a sonographic examination performed at 19 weeks' gestation. Furthermore, our case exhibits a rare type of multiple-marker screening result with increased maternal serum alpha-fetoprotein. This case demonstrates the need for thorough sonographic evaluation of the fetal thoracoabdominal wall as early as possible, because fetal ectopia cordis can be the major abnormality of trisomy 18.

Prenatal diagnosis of trisomy 18: report of 30 cases

OBJECTIVES

To review the detection rate of the prenatal screening tests used for the diagnosis of the trisomy 18.

METHODS

From 1 October 1998 to 31 December 2001, we reviewed the database and medical records of 30 cases of trisomy 18. All were singletons and trisomy 18 was confirmed by amniocentesis in 19 cases, by cordocentesis in 6 cases, by chorionic villi sampling in 2 cases and by skin biopsy in 3 cases.

RESULTS

Of the 30 study cases, 23 cases (77%) were offered genetic study due to abnormal ultrasound (US) findings. Twelve (40%) out of the 23 cases were due to abnormal US findings detected before the triple test and 11 (37%) were due to abnormal US findings after the normal triple test. Six cases (20%) were offered genetic study because of an abnormal triple test, and one case was offered genetic study due to advanced maternal age only. Including the second targeted ultrasonogram, one or more abnormal US findings were found in all 30 fetuses.

CONCLUSIONS

Abnormal US finding is the most sensitive screening test for trisomy 18. The most sensitive ultrasonographic finding for trisomy 18 at under 16 weeks of gestation is increased nuchal translucency (75%) and, after 16 weeks, is cardiac defect (83%).