Outcome of cases of de novo structural rearrangements diagnosed at amniocentesis

The frequency of de novo rearrangements at amniocentesis was determined in 76952 prenatal diagnoses from centres in the United States. Rates for balanced rearrangements are slightly greater than rates previously reported in the newborn, possibly because banding studies were not used in the latter. Rates for unbalanced rearrangements are considerably higher in the amniocentesis data not only because banding was used but also because a substantial loss of abnormal conceptions is to be expected between amniocentesis and birth. The higher frequency of cases with supernumerary markers at amniocentesis is unexplained. A review of 66 apparently balanced de novo rearrangements found at amniocentesis revealed evidence of abnormality in five; in four of these the abnormality was noted in the abortus. The number of cases observed is still too small to rule out a risk of abnormality no greater than the usual rate of abnormalities at birth. Abnormalities were detected in 6 of 10 cases with unbalanced de novo rearrangements. In 33 cases of non-familial supernumerary chromosomes 6 (18.2 per cent) showed abnormality. Non-satellited markers appeared to have a higher rate of abnormality than satellited markers but the difference is not statistically significant. Further studies and improved follow-up of de NOVO cases diagnosed at amniocentesis are required.     

Cytogenetic analysis of chorionic villi for prenatal diagnosis: An ACC collaborative study of U.K. data

A prospective 3-year collaborative study was undertaken in 1987 to collect cytogenetic data from diagnostic chorionic villus samples (CVS) in the U.K. in order to determine the predictive value of the chromosome abnormalities encountered. Twenty-seven laboratories contributed a total number of 7595 cases, of which 97·6 per cent were successful. Excluding single cell anomalies, a total of 480 cytogenetic abnormalities were reported, of which 137 were familial structural rearrangements and 343 were de novo problems. Non-mosaic trisomies of chromosomes 13, 18, and 21 (n=157), non-mosaic sex chromosome abnormalities (n=33), and triploidy (n=6) were all confirmed in cells of fetal origin where follow-up information was available. Of the nine remaining non-mosaics including tetraploidy, trisomies of other autosomes, and extra markers, only a trisomy 16 and a case of a supernumerary marker proved genuine. Eighty-eight cases of mosaicism were reported to the study, of which only nine were confirmed as genuine: two cases involving chromosome 13, one trisomy 18, two examples of extra marker chromosomes, three 45,X, and one 47,XXX. There were no reports of false-negative findings. Presumptive maternal cell contamination was encountered in 39 cases, a detected incidence of 0·5 per cent. Four cases of presumptive ‘vanishing twin’ were recorded: in three of these, direct preparations showed a female karyotype, whereas cultures indicated a male (with male fetuses in two cases). The fourth case was of a female fetus with male and female cells in the CVS cultures. Subtle structural chromosome abnormalities were missed in three instances. Accurate prediction of the fetal karyotype was shown to require detailed knowledge of both the nature and the distribution of abnormal cells in the extra-embryonic tissues. In many cases, this could only be made where results from direct preparations and cultured cells were available. A number of conclusions were reached from these and similar data in the literature regarding the reliability of chromosome findings in CVS.     

Characterization of marker chromosomes by microdissection and fluorescence in situ hybridization

We characterized by microdissection and fluorescence in situ hybridization (FISH) two marker chromosomes: (1) a de novo, acrocentric marker chromosome detected in 88 per cent of the amniotic fluid cells of one of two physically and developmentally normal twins; and (2) a metacentric marker chromosome present in a phenotypically normal female. Analysis of FISH probes developed from the marker chromosomes indicated that the marker chromosomes in cases 1 and 2 were del(14)(q11) and a derivative chromosome from a Robertsonian translocation, respectively. Microdissection in combination with FISH may prove to be a valuable technique in determining the chromosomal origin of de novo marker chromosomes and unbalanced structural rearrangements detected during prenatal diagnosis.     

Mosaicism of autosomes and sex chromosomes in morphologically normal,monospermic preimplantation human embryos

We have previously detected chromosome abnormalities in human embryos whilst identifying the sex for preimplantation diagnosis of X-linked disease. In this study we assess the incidence of these abnormalities, both for sex chromosomes and autosomes 1 and 17, using dual fluorescent in situ hybridization (FISH). Sixty-nine normally fertilized embryos of good morphology at the 6–10 cell stage (day 3 post-insemination) were examined. The embryos were spread whole using HCl and Tween 20 to dissolve the cytoplasm. Thirty-four embryos were analysed for the sex chromosomes and 35 for autosomes 1 and 17. All probes were directly labelled with fluorochromes allowing analysis in 2 h. Control lymphocytes demonstrated that the probes were of high specificity. For the sex chromosomes, five embryos were mosaic (15 per cent) with the remaining 29 being uniformly XX or XY. In no case was an XX nucleus found in an otherwise XY embryo, indicating that even though mosaicism for the sex chromosomes is present, such abnormalities would not lead to a misdiagnosis of sex. For the autosomes, 16 embryos were abnormal (46 per cent); one embryo was triploid, one was monosomic for chromosome 1, and ten others were diploid mosaics (three diploid/aneuploid, three diploid/polyploid, and four diploid/haploid). A further four embryos had variable chromosome numbers in the majority of nuclei which appeared to be the result of uncontrolled mitotic division. The presence of haploidy or double monosomy, which occurred in 15 per cent of nuclei, has important implications for the diagnosis of trisomies and dominant disorders.     

Likely pathogenic variant in the BICD2 gene in fetus presenting with non-immune hydrops

Trio exome sequencing was performed on a fetus presenting with severe hydrops fetalis at 21 + 0 weeks gestation. A novel de novo BICD2 missense variant was identified in the fetus. Pathogenic variants in the BICD2 gene are associated with lower extremity-predominant spinal muscular atrophy. The variant was initially classified as a variant of uncertain clinical significance (VUS) as at the time of analysis and initial report, pathogenic variants in the BICD2 gene specifically had not been associated with fetal hydrops and no other abnormalities had been detected. It was agreed in multidisciplinary team discussions to include the variant in the report as a VUS recommending phenotypic follow-up. The pregnancy was terminated and post-mortem findings were in keeping with a BICD2-pathogenic variant. In addition, a paper was published reporting another case with a pathogenic BICD2 variant presenting with fetal hydrops. The variant classification was then upgraded to class 4 likely pathogenic and reported as consistent with the diagnosis. This case demonstrates the importance of reporting these new gene/phenotypes in enabling others in the classification of variants, staying up-to-date with literature and following up phenotype for class 3 variants of interest.     

Prenatal diagnosis of a homologous Robertsonian translocation involving chromosome 15

We report the prenatal diagnosis of a fetus with a de novo Robertsonian translocation: 45,XY,der(15;15)(q10;q10). Although Robertsonian translocations are common chromosomal rearrangements, those involving homologous chromosomes are infrequent. Since chromosome 15 is imprinted, uniparental disomy (UPD) is a concern when chromosomal rearrangements involving chromosome 15 are identified. In the present case, UPD studies showed normal biparental inheritance. In contrast to the fact that most homologous acrocentric rearrangements are isochromosomes, these results indicate postzygotic formation of a Robertsonian translocation between biparentally inherited chromosomes 15. Copyright © 2001 John Wiley & Sons, Ltd.     

Morphological and cytogenetic analysis of intact oocytes and blocked zygotes

We examined cytological and cytogenetic parameters of 1076 oocytes and 385 zygotes that failed to develop post in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI). Out of 1076 oocytes, 894 (83%) arrested oocytes showed a first polar body and were thus assumed arrested at metaphase II while the remainder showed no polar body. In the group of oocytes with a polar body, 20.5% had an abnormal karyotype. Cytologically, premature sperm chromosome condensation was noted in 28.3% of uncleaved oocytes. This high PCC can be explained by the different grades of oocyte maturity from one center to another. Oocytes from older women showed no increased aneuploidy but did show increased premature chromosome condensation. Analysis by classical technique of 220 uncleaved zygotes showed 91 with highly condensed chromosomes, 53 with asynchrony of condensation, 31 with pulverized chromosomes, and 45 arrested at the first somatic metaphase. Out of 385 arrested zygotes, 165 were explored by in situ hybridization. FISH using a set of 7 chromosome-specific probes showed aneuploidy in the chromosomes analyzed (13, 16, 18, 21, 22, X, Y) in 21.8% of blocked zygotes (19–25% depending on morphology). Extrapolating to other chromosomes, we expect that a vast majority of blocked zygotes and oocytes probably carry chromosome abnormalities. These data demonstrate the contributions of chromosome disorder in early embryo development blocking and implantation failure. Certainly, the issue of cytoplasm and nuclear immaturity and their relation to each other and to chromosome abnormalities provides a fertile area for future investigation in ART. Copyright © 2003 John Wiley & Sons, Ltd.     

Transabdominal chorionic villus sampling in the second and third trimesters of pregnancy: Chromosome quality,reporting time,and feto-maternal bleeding

Transabdominal chorionic villus sampling (TA-CVS) was performed in 210 pregnancies from 13 to 38 weeks using a double-needle technique. The sampling success was comparable to first-trimester TA-CVS and the diagnostic success rate was 98.2 per cent for the short-term technique and 99.3 per cent for cultured villi. Two fetuses could not be karyotyped. We found the chromosome quality to be similar to that in the first trimester, comparing the number of G-bands and other chromosome attributes. There were no unintended losses in a group (n = 142) with no sonographic abnormality, except for one death in utero at 38 weeks, 20 weeks after sampling. Chromosomal aberrations were seen in 19 per cent of cases with abnormal sonograms (n = 58). One case of a discordant karyotype was found (false-negative prediction of Down's syndrome by the short-term preparation). There were no cases of fetal demise due to feto-maternal bleeding. It is suggested that double-needle TA-CVS in advanced pregnancies combines the advantages of rapid karyotyping of chromosomes of good quality and low risk for the fetus, and seems to be easier to practise and is probably safer than cordocentesis.     

A 10-year survey, 1980–1990, of prenatally diagnosed small supernumerary marker chromosomes,identified by fish analysis. Outcome and follow-up of 14 cases diagnosed in a series of 12 699 prenatal samples

A cytogenetic survey and follow-up studies were made of 14 cases with supernumerary marker chromosomes, identified among 12 699 prenatal samples, investigated at our institution over a 10-year period from 1980 to 1990. FISH (fluorescence in situ hybridization) techniques were employed to identify the chromosomal origin of the marker chromosomes. Five cases were familial, all derived from acrocentric chromosomes, and all without apparent phenotypic effects in the children. Nine cases represented de novo aberrations. In two cases (one with a marker from chromosome 14 or 22, the other with a ring-like marker derived from chromosome 17), the pregnancies continued and apparently normal babies were delivered at term, but the child with a marker derived from chromosome 17 showed slight psychomotor retardation at 2 years of age. All other pregnancies with de novo markers were terminated. In three cases, significant abnormalities were found at autopsy. One of these had an isochromosome 12p and the phenotype was consistent with Pallister-Killian syndrome. In conclusion, marker chromosome identification, as well as clinical follow-up, is essential for the purpose of improving genetic counselling.     

Correlation between phenotypic expression of de novo marker chromosomes and genomic organization using replicational banding

It has been suggested that actively expressed genes are primarily located in early replicating bands. This hypothesis is supported by cytogenetic and pregnancy outcome data from four consecutive cases of prenatally detected de novo marker chromosomes. Two fetuses with major anomalies had large early replicating bands, while the marker in a third phenotypically normal fetus was late replicating. In the fourth case, a ring marker chromosome had only a small early replicating region. Pregnancy termination was elected. While no structural malformations were apparent, potential intellectual function in this case remains unresolved. An understanding of the relationship between genomic organization and chromosome banding is critical in counseling for prenatally detected de novo marker chromosomes. Replicational banding is particularly helpful in recognizing genes that may be actively expressed and result in developmental abnormality.     

Prenatal diagnosis of a craniopharyngioma using ultrasonography and magnetic resonance imaging

We report an infant with a craniopharyngioma which was detected in utero. Maternal uterine ultrasonography, done at 27 weeks because of polyhydramnios, revealed a 4 cm midline mass near the base of the fetal skull. At 31 weeks, magnetic resonance imaging of the maternal abdomen confirmed the presence of a mass in the region of the third ventricle and revealed hydrocephalus. Two days post-partum a computed tomography (CT)-guided needle biopsy of the mass was performed and recovered tissue which was histologically consistent with a craniopharyngioma. The infant' s postnatal period was complicated by seizures, which were treated with phenobarbital, and by progressive hydrocephalus, necessitating placement of a ventriculo-peritoneal shunt. He also received therapy for central hypothyroidism and diabetes insipidus. The infant' s parents refused permission for attempted resection of the tumour and he died at 8 weeks of age. This represents the second reported case of an antenatally detected craniopharyngioma. Four other cases of different intracranial tumours have been detected in utero using ultrasound, with no reported survivors past 3 days of age. There is a uniformly poor prognosis of such infants, but earlier diagnosis and intervention may change this result.     

A familial Xp+ chromosome detected during fetal karyotyping,which is associated with short stature in four generations of a Turkish family

The short-stature homeobox-containing gene (SHOX) on chromosome Xp22.3 was recently identified as an important determinant of the stature phenotype. Deletions of the SHOX gene, some of them due to structural chromosome abnormalities, have been described in patients with idiopathic short stature and Leri-Weill syndrome. Additionally, haploinsufficiency of SHOX is a main cause for short stature seen in patients with Turner syndrome. Here we report an unusual X-chromosome abnormality, which was detected during a fetal karyotyping performed because of a previous child with Down syndrome. GTG banding demonstrated an extra chromosome segment on the terminal part of the short arm of chromosome X in the index case (karyotype: 46,X,Xp+). The same chromosomal abnormality was found in the mother and the maternal grandmother. All carriers of this chromosomal abnormality presented with short stature but no other associated symptoms. Whole chromosome painting of X revealed a homogeneous painting of the abnormal X chromosome indicating that no other chromosome was involved. Additional FISH studies with probe DXS1140 (Kallmann probe at Xp22.3), Quint-Essential X-Specific DNA (DMD probe at Xp21.2), XIST (at Xq13.2), and Tel Xq/Yq were performed, and no abnormality was observed in the intensities or the localizations of the probes signals. However, applying a specific SHOX gene probe (derived from cosmid LLNONO3M34F5) showed a loss of signal on the derivative X chromosome. Our results show that the Xp+ generation led to a deletion of the complete SHOX gene and caused short stature in the presented family. Copyright © 2003 John Wiley & Sons, Ltd.     

Renatal diagnosis of mosaic tetrasomy 12p/trisomy 12p by fluorescent in situ hybridization in amniotic fluid cells: A case report of pallister–killian syndrome

A prenatally detected case of a rare mosaic tetrasomy 12p/trisomy 12p is reported, presenting as the well-known accessory isochromosome 12p and a supernumerary single 12p marker in 17/24 and 6/24 clones of cultured amniotic fluid cells, respectively. The chromosomal nature of both marker chromosomes was investigated in cultured amniotic fluid cells by fluorescent in situ hybridization with various probes: the 12-centromeric probes pa12H8 and D12Z3, a whole chromosome 12 paint, and the chromosome 12p-specific paint M28. DNA analysis revealed a maternal origin of the extra 12p material. After counselling, the parents requested termination of pregnancy. Inspection and autopsy of the fetus revealed many of the dysmorphisms and internal structural abnormalities of the Pallister–Killian syndrome.     

Prenatal treatment of fetal hydrops associated with the hypertelorism-dysphagia syndrome (opitz-g syndrome)

Non-immunological fetal hydrops diagnosed prenatally presents a difficult diagnostic and therapeutic problem. In the case presented, fetal hydrops was recognized at 19 weeks gestation and no specific cause was found prenatally in spite of extensive investigations. The fetal hydrops was treated in utero by thoracocentesis and an intravenous infusion of albumin carried out at fetoscopy. After birth the infant was recognized to have the hypertelorismdysphagia syndrome (or Opitz-G syndrome, McK no. 30710). This autosomal dominant syndrome consists of hypertelorism, laryngeal abnormalities, swallowing difficulties, hyprospadias and an imperforate anus. Fetal hydrops has been reported on one previous occasion in this syndrome. The intrauterine treatment given in this case may have been successful in reducing the neonatal complications of the Opitz-G syndrome.     

Detection of fetal cells in transcervical samples and prenatal diagnosis of chromosomal abnormalities

Transcervical samples collected by lavage, aspiration, and cytobrush from women between 6 and 13 weeks of gestation were tested for the presence of fetal cells using fluorescence in situ hybridization (FISH) with probes for chromosomes X, Y, 1, and 21, and by polymerase chain reaction (PCR) amplification of DNA sequences derived from chromosomes X, Y, and 21. With a few exceptions, a good correlation was observed between the results of sexing the fetuses using FISH or PCR on transcervical cell (TCC) samples retrieved by lavage and those obtained by testing fetal (placental) tissue. In a comparative study between TCC samples collected by lavage or cytobrush, the sex of the fetus was correctly diagnosed by PCR amplification of a Y-derived DNA sequence. Variable results were observed with samples obtained by aspiration, mainly because this procedure was found to be more prone to failure to remove thick mucus without previous injection of physiological saline. Chromosome 21-derived small tandem repeats (STRs) of fetal origin were successfully detected in about 40 per cent of TCC samples recovered by lavage. Two cases of chromosomal abnormalities, one of trisomy 21 and one of triploidy, were detected in TCC samples in the course of our investigations.     

Karyotype abnormalities in fetuses diagnosed as abnormal on ultrasound before 20 weeks' gestational age

This study examined rates of karyotype abnormalities in fetuses diagnosed by ultrasound as abnormal before 20 weeks' gestational age and which prompted a follow-up amniocentesis or chorionic villus sampling. Those diagnosed before 20 weeks were compared with those diagnosed at or after 20 weeks. A retrospective study identified ultrasonographically abnormal fetuses in whom karyotyping had been undertaken, 306 fetuses before 20 weeks' gestational age and 241 after. Isolated malformations before 20 weeks had, on average, an 18 per cent risk of karyotype abnormality, compared with 20 per cent later. Specific rates were calculated; for example, heart abnormality was associated with karyotype abnormality in 7 per cent of cases before 20 weeks and in 14 per cent later. Multiple malformations and karyotype abnormalities were found together in 28 per cent of fetuses prior to 20 weeks and in 33 per cent of the older fetuses. Specific associations included nuchal oedema and trisomy 21 in 21 per cent of fetuses before 20 weeks. No karyotype abnormalities were found in fetuses diagnosed with choroid plexus cysts. An overview of trisomies in Victoria, in 1991, showed that 50 per cent of trisomy 18, 42 per cent of trisomy 13, and 9·5 per cent of trisomy 21 cases were identified by ultrasound in women less than 37 years of age. Another 28·6 per cent of trisomy 21 fetuses were detected in women of advanced maternal age who underwent amniocentesis or chorionic villus sampling, making a total of 38·1 per cent of trisomy 21 that were detected prenatally. The importance of early karyotyping specifically relates to the ongoing management of the pregnancy if the chromosomes are normal, and facilitates decision-making regarding termination of pregnancy if the chromosomes are abnormal.     

Prenatal diagnosis of congenital cytomegalovirus infection in 189 pregnancies with known outcome

An Erratum has been published for this article in Prenatal Diagnosis 21(7) 2001, 605. Prenatal diagnosis (PD) of fetal cytomegalovirus (CMV) infection was performed in 242 pregnancies, with known outcome in 189 cases. In 141/189 pregnancies, PD was carried out on account of suspicious maternal CMV serology up to gestational week (WG) 23, and in 48 cases on account of abnormal ultrasonic findings detected between WG 18 and 39. Chorionic villus samples (n=6), amniotic fluid (AF, n=176) and/or fetal blood specimens (n=80) were investigated for detection of virus by cell culture, shell vial assay, PCR and/or CMV-specific IgM antibodies. Of 189 fetuses correctly evaluated by CMV detection either in fetal tissue following therapeutic abortion/stillbirth (n=24) or in urine of neonates within the first 2 weeks of life (n=33), 57 were congenitally infected. In women with proven or suspected primary infection, the intrauterine transmission rates were 20.6% (7/34) and 24.4% (10/41), respectively. Of the congenitally infected live-born infants, 57.6% (19/33) had symptoms of varying degree. The overall sensitivity of PD in the serologic and ultrasound risk groups was 89.5% (51/57). A sensitivity of 100% was achieved by combining detection of CMV-DNA and CMV-specific IgM in fetal blood or by combined testing of AF and fetal blood for CMV-DNA or IgM antibodies. There was no instance of intrauterine death following the invasive procedure. The predictive value of PD for fetal infection was 95.7% (132/138) for negative results and 100% (51/51) for positive results. Correct results for congenital CMV infection by testing AF samples can be expected with samples obtained after WG 21 and after a time interval of at least 6 weeks between first diagnosis of maternal infection and PD. In case of negative findings in AF or fetal blood and the absence of ultrasound abnormalities at WG 22–23, fetal infection and neonatal disease could be excluded with high confidence. Positive findings for CMV infection in AF and/or fetal blood in combination with CMV suspicious ultrasound abnormalities predicted a high risk of cytomegalic inclusion disease (CID). Furthermore, detection of specific IgM antibodies in fetal blood was significantly correlated with severe outcome for the fetus or the newborn (p=0.0224). However, normal ultrasound of infected fetuses at WG 22–23 can neither completely exclude an abnormal ultrasound at a later WG and the birth of a severely damaged child nor the birth of neonates which are afflicted by single manifestations at birth or later and of the kind which are not detectable by currently available ultrasonographic techniques. Copyright © 2001 John Wiley & Sons, Ltd.     

Marker chromosomes in A series of 10000 prenatal diagnoses. Cytogenetic and follow-up studies

In a series of 10 000 prenatal diagnoses 15 marker chromosomes were detected in our centre. Six of these were familial whilst nine had originated de novo. They were analysed with various staining methods. DA-DAPI staining was positive in nine out of 12 pregnancies. Six pregnancies were continued. Five normal children were born, one ended in intrauterine fetal death of a normal fetus at 37 weeks. Nine pregnancies were terminated, showing six normal fetuses, one familial cat-eye syndrome, one fetus with Down syndrome caused by additional trisomy 21 and one fetus with cystic kidneys resp. It is concluded that it seems safe to continue the pregnancy in cases of a familial marker, identical to that of one parent, whilst a de novo DA-DAPI positive marker seems to present a low risk for fetal anomalies.     

A study of chromosomal aberrations in amniotic fluid cell cultures

This paper represents the analysis of 1916 routine amniotic fluid specimens harvested by an in situ fixation technique in a prospective study with regard to cultural chromosome anomalies. Excluding constitutional abnormalities, 2·9 per cent of 19432 cells analysed showed some form of chromosome anomaly, terminal deletions (57 percent) and chromatid/chromosome breaks and gaps (18 per cent) being the most frequent, followed by interchange aberrations (13 per cent) and trisomy (5 per cent). No case was found of more than one colony from the same culture showing the same anomaly without it being present in other cultures from the same fluid. The wholly abnormal colonies had a surplus of trisomies and from the mathematical considerations presented one may infer that these are likely to reflect the presence of abnormal cells in the amniotic fluid. Partly abnormal colonies appeared at a frequency that would correspond to virtual absence of selection against chromosomally abnormal cells when cultured in vitro. The aberrations found were similar to those seen as single cell anomalies, except for chromatid breaks and exchanges. The data suggest a basic preferential induction of trisomy for chromosomes 2,18,21, and the Y-chromosome. Structural aberrations showed a marked clustering of breakpoints around the centromeres. The frequency of mutant cells was low (1·4 × 10⁻³) before culture was initiated. At harvest, the frequency of abnormal cells was much higher (3 × 10⁻²) corresponding to 3 × 10⁻³ mutations per cell per generation accumulating over approximately ten generations in vitro.