Apparent confined placental mosaicism of trisomy 16 and multiple fetal anomalies: case report

Trisomy 16 is frequently found confined to the placenta (confined placental mosaicism (CPM)), with a structurally normal fetus. In some cases of trisomy 16, the fetus has uniparental disomy for chromosome 16 (UPD16) which is associated with intrauterine growth restriction (IUGR) and fetal anomalies. We report a case of apparent confined placental mosaicism for trisomy 16, using standard cytogenetic techniques, but with multiple fetal abnormalities including congenital diaphragmatic hernia in which there was no evidence of UPD in the disomic tissues examined. Subsequent examination of fetal tissues using fluorescent in situ hybridization (FISH) demonstrated low levels of mosaicism for trisomy 16 in all the tissues examined. The use of FISH permits identification of mosaicism which conventional techniques may not identify.     

Prenatal diagnosis of trisomy 21 without the Down syndrome phenotype

OBJECTIVE: To report a patient with the prenatal diagnosis of trisomy 21 without the clinical Down syndrome (DS) phenotype secondary to the absence of the Down syndrome chromosomal region (DSCR) in a derivative chromosome 21. CASE REPORT AND METHODS: A newborn patient with prenatal diagnosis of duodenal atresia. Cytogenetic studies revealed a regular trisomy 21. At birth, she did not present the clinical features of DS. FISH analysis was performed in the patient with the LSI spectrum probe for the DSCR and in the mother with FISH multicolor analysis using painting probes for chromosomes 20 and 21. RESULTS: FISH analysis in the patient showed two hybridization signals suggesting that the third chromosome 21 did not have the DSCR region explaining the absence of the DS phenotype. FISH multicolor analysis in the mother showed three hybridization signals for chromosomes 20 and 21, concluding a maternal karyotype, 46,XX,t(20;21)(p11.2;q22.1). CONCLUSIONS: The patient was found to have a derivative chromosome 21 secondary to a nondisjunction error in meiosis II without the DS critical region and the phenotype was mostly secondary to the combination of the two partial trisomies.     

An infant with trisomy 9 mosaicism presenting as a complete trisomy 9 by amniocentesis.

We present a case in which amniocentesis performed at 33 weeks' gestation because of symmetrical intrauterine growth retardation and decreased amniotic fluid volume led to the prenatal diagnosis of a fetus with a karyotype of 47,XX,+9,t(1;20)(q42;p11.2) pat, i.e., with an extra chromosome 9 and a balanced translocation between chromosomes 1 and 20. At delivery, the baby showed clinical features of trisomy 9, yet chromosome analysis of the cord blood revealed no trisomy 9 cells, a finding confirmed by neonatal blood karyotyping. The balanced translocation was present in all cells. A skin biopsy confirmed trisomy 9 mosaicism with 10 per cent trisomy 9 cells. The baby died at 6 weeks and an autopsy was obtained. Chromosome analysis of different organs demonstrated different frequencies of the mosaicism of trisomy 9. The possible underlying mechanism for the discrepancy between the karyotype results by amniocentesis and those of other tissues is discussed.     

Complete discrepancy between QF-PCR analysis of uncultured villi and karyotyping of cultured cells in the prenatal diagnosis of trisomy 21 in three CVS

OBJECTIVE: To investigate complete discrepancies in the prenatal diagnosis of trisomy 21 between QF-PCR analysis of uncultured villi and karyotyping of cultured cells in three chorion villus samples. METHODS: Clinical details were obtained from all three patients. Follow-up studies were undertaken where possible by evaluation of chromosome 21 copy number with QF-PCR, interphase FISH, MLPA and karyotyping, and by post-mortem examination. RESULTS: Case 1: severe oligohydramnios and microcephaly on scan. QF-PCR: trisomy 21; MLPA: trisomy 21; cultured karyotype: 46,XY[48]. Placental and fetal tissue results and post-mortem examination indicated a euploid fetus with trisomy 21 mosaicism confined to the placenta. Case 2: Down screen risk 1:16; NT = 4.4 mm; absent nasal bone (Caucasian mother). QF-PCR: disomy 21; cultured karyotype: 47,XY,+ 21[23]. Neck thickening noted at delivery-post-mortem refused, no fetal tissue available. Placental tissue indicated mosaicism for trisomy 21. Case 3: Down screen risk 1:91; NT = 6.7 mm. QF-PCR: disomy 21; cultured karyotype: 46,XX,der(21;21)(q10;q10)[60]. No follow-up possible. PCR genotyping of cultured cells confirmed sample identity in all three cases. Chromosome 21 markers observed by PCR were biallelic in all three cases, indicating that a mitotic error could account for the presence of the abnormal cell lines in each case. CONCLUSION: QF-PCR analysis of uncultured villi and cultured karyotyping may rarely show complete discrepancy in the prediction of fetal trisomy 21 in CVS. Within-biopsy sample mosaicism, together with the testing of different cell populations, provide an explanation for these results. Practical ways to minimise the risk of such discrepancy are proposed.     

Maternal serum screening in cases of mosaic and translocation Down syndrome

OBJECTIVES: To determine if the second-trimester maternal serum markers (MSM) screening for Down syndrome (DS) is efficient in DS mosaicism or structural rearrangement cases. METHOD: DS mosaic or translocation cases were reviewed from databases of routine MSM DS screening. The control group consisted of 977 trisomy 21 cases included in a series of 854 902 patients (routine screening). DS risk was calculated by combination of maternal age and MSM [alpha-fetoprotein (AFP) and human choriogonadotrophin (hCG) or free beta-hCG and/or uE3] expressed in multiples of median (MoM). Mosaic DS cases were divided into three groups, < 10%, 10-49%, and >or= 50% trisomy 21 cells. Translocation DS cases were divided into three groups, isochromosome, Robertsonian, or reciprocal translocation. Detection rate (DR) and MoMs were evaluated in each group. RESULTS: As many as 76 cases of nonstandard trisomy 21 were collected. For mosaic DS cases (n = 43) DR was 69.8% (not significantly different from the 70.8% of control group). When mosaicism was less than 10%, the DR dropped to 25%. For translocation DS cases (n = 33) DR was 75.7% (not significantly different from control group) whatever the types of translocation. CONCLUSION: In the nonstandard DS cases, second-trimester MSMs gave the same detection rate as for standard trisomy 21, except the cases with low-level mosaicism (<10%).     

Prenatal diagnosis of trisomy 3 mosaicism

OBJECTIVES: To present the clinical, cytogenetic, and molecular cytogenetic findings of prenatally diagnosed trisomy 3 mosaicism. CASE AND METHODS: Trisomy 3 mosaicism is rare, and only two cases of prenatally diagnosed trisomy 3 mosaicism have been reported. Amniocentesis, performed for AMA, revealed a karyotype of 47,XX, + 3[8]/46,XX[27]. Periumbilical blood sampling (PUBS) showed 46,XX in 100 cells. Fluorescence in situ hybridization (FISH) analysis using an alpha satellite chromosome 3 probe confirmed the cytogenetic findings. A repeat amniocentesis confirmed mosaicism for trisomy 3 (47,XX, + 3[1]/46,XX[18]). The infant was delivered by elective C-section because of the presence of IUGR and oligohydramnios. The baby had normal physical findings at birth except for symmetric IUGR, apparently resulting from the placental trisomic cell lines. At delivery, chromosome analysis of 50 cells each from blood, placenta, and umbilical cord revealed 46,XX in all cells. FISH analysis of amniotic fluid cells (54 nuclei), peripheral blood (50 nuclei), umbilical cord fibroblasts (57 nuclei), and placental tissue (52 nuclei) demonstrated two signals in 200 nuclei (i.e., 46,XX) and three signals in 13 nuclei (i.e., 47,XX, + 3). At 11 months of age, the baby was progressing normally. CONCLUSION: A diagnosis of trisomy 3 mosaicism is problematic for patients and clinicians. This is only the third case of trisomy 3 mosaicism identified at amniocentesis. Ultrasound, PUBS, and evaluation of placental tissues and postnatal peripheral blood, were useful in providing information regarding the fetal involvement of trisomy 3. Additional cases of prenatally diagnosed mosaicism for rare trisomies are necessary to more accurately assess the significance of these findings.     

Severe intrauterine growth restriction and trisomy 15 confined placental mosaicism: a case report and review of literature

OBJECTIVES: To correlate confined placental mosaicism (CPM) for trisomy 15 with severe intrauterine growth restriction (IUGR) and early death after birth (age of 6 months). METHODS: Chromosome analysis was performed on amniotic fluid at 21st week of gestation, on peripheral blood at birth and on fibroblasts at death using conventional techniques. FISH was performed with Chromoprobe I-Multiprobe System kit and commercial probes according to manufacturer's protocol. DNA was extracted from parental and child peripheral blood, placenta tissue and skin fibroblasts, and UPD tests were done with microsatellites selected from Genome Data Base. RESULTS: The child presented severe hypospadias, micropenis, bilateral cryptorchidism and bifid scrotum, inguinal hernia, dolichomegacolon, severe thymic lymphatic depletion and heart hypertrophy, mainly involving right ventricle. Mosaic trisomy 15 (84%) was discovered by FISH on placental biopsy at term. Uniparental disomy (UPD) for chromosome 15 was excluded. Prenatal (amniotic fluid), postnatal (peripheral blood) karyotypes and analysis on skin fibroblast metaphases were normal. Since the autopsy showed some features suggesting genetic syndromes, such as CATCH22, Williams-Beuren syndrome, matUPD2, we excluded the presence of all these diseases. CONCLUSIONS: The only explanation for this clinical case seems to be the presence of tris15CPM that is reported as one of IUGR causes.     

Cytogenetic analysis of trophoblasts by comparative genomic hybridization in embryo-fetal development anomalies

Cytogenetic studies of spontaneous abortions or intrauterine fetal death depend on conventional tissue culturing and karyotyping. This technique has limitations such as culture failure and selective growth of maternal cells. Fluorescent in situ hybridization (FISH) using specific probes permits diagnosis of aneuploidies but is limited to one or a few chromosomal regions. Comparative genomic hybridization (CGH) provides an overview of chromosomal gains and losses in a single hybridization directly from DNA samples. In a prospective study, we analyzed by CGH trophoblast cells from 21 fetuses in cases of spontaneous abortions, intrauterine fetal death or polymalformed syndrome. Six numerical chromosomal abnormalities including one trisomy 7, one trisomy 10, three trisomies 18, one trisomy 21 and one monosomy X have been correctly identified by CGH. One structural abnormality of the long arm of chromosome 1 has been characterized by CGH. One triploidy and two balanced pericentromeric inversions of chromosome 9 have not been identified by CGH. Sexual chromosomal constitutions were concordant by both classical cytogenetic technique and CGH. Contribution of trophoblast analysis by CGH in embryo-fetal development anomalies is discussed.     

Prenatal diagnosis of de novo trisomy 1(q21-qter)der(Y)t(Y;1) in a malformed live born

OBJECTIVES: To present the prenatal diagnosis case of pure trisomy 1q21-qter with translocation to chromosome Y in all cells analysed. CASE: Amniocentesis for chromosomal analysis was performed at 15 gestational weeks because it showed a fetal nuchal thickness by ultrasound examination. GTG banding and FISH analysis were carried out. RESULTS: In spite of the unfavourable fetal prognosis, the couple decided to continue the gestation. Ultrasonographic controls performed between the 20th and 34th weeks showed a male fetus with multiple abnormalities. The propositus was born at 35 weeks' gestation, surviving 40 min. CONCLUSION: Our patient's clinical anomalies were compared with two cases of trisomy 1q in all cells and five mosaicisms with the object of defining this syndrome, which we consider important for future genetic counselling.     

Variable levels of mosaicism for trisomy 21 in a non-immune hydropic infant with chylothorax.

We report the first case of mosaic trisomy 21 with non-immune hydrops fetalis and bilateral chylothoraces. Prenatal fetal blood karyotype analysis of 15 fetal cells revealed a 46,XX karyotype. Aggressive prenatal management, including fetal thoracocentesis and pleuro-amniotic shunt, was performed. A clinical phenotype of Down syndrome was apparent after the gross oedema had subsided. Subsequent chromosome study of neonatal blood lymphocytes showed mosaic trisomy 21 with 23 per cent trisomic cells. Review of the initial fetal blood sample identified trisomy in 5 per cent of 134 cells. Follow-up study at five months showed no trisomy 21 in 100 cells. This case illustrates the variable levels of mosaicism manifest in the peripheral blood of an infant with obvious Down syndrome phenotype, and the limitation of cytogenetic analysis of peripheral lymphocytes alone in prenatal and postnatal detection of low levels of mosaicism.     

Hydrops fetalis, thickened placenta and other sonographic findings in a low-level trisomy 21 mosaicism: a case report

We report a case of trisomy 21 mosaicism detected upon amniocentesis in a 36-year-old woman. Ultrasound examination at 23 weeks' gestation showed a fetus with hydrops, pulmonary hypoplasia, oligohydramnios, thickened placenta, and intrauterine growth retardation. Cytogenetic analysis revealed low-percentage (6%) mosaicism for trisomy 21. Hydrops fetalis and thickened placenta are uncommon findings in fetuses affected by trisomy 21 mosaicism. A short review of the literature is given regarding the sonographic findings associated with trisomy 21 mosaicism, and the genetic counseling in such cases.     

Correlation of abnormal rapid FISH and chromosome results from amniocytes for prenatal diagnosis

Rapid fluorescence in situ hybridization (FISH) performed on 1,788 amniocenteses, using Aneuvision (Vysis) probes for chromosomes 13, 18, 21, X, and Y, over several years, yielded 115 cases with percentages of aneuploidy between 4 and 100%. All cases above 60% were confirmed to be positive by chromosome analysis. Fifteen of forty-one cases that would be considered inconclusive by generally accepted criteria (i.e. with less than 60% of cells with an abnormal signal pattern) revealed lower cutoffs to be positive when confirmed by chromosome analysis. For trisomy 21, 6 cases with percentages from 36 to 57% were positive; 4 of 7 cases with percentages from 22.5 to 33% were positive; 11 cases with percentages of 13% or less were negative. Similar trends were found for aneuploidies of 13, 18, X, and Y. However, the number of abnormal cases is still too small to determine definitive cutoffs in the <60% gray zone. An average of 57 metaphases was analyzed for cases with FISH percentages below 60%. Despite the wide range of abnormal FISH percentages for chromosomally positive cases, we found no examples of autosomal mosaicism in this series. Although sex chromosome mosaicism was cytogenetically evident in several cases, there was little direct correlation between cytogenetic and rapid FISH results. FISH results involving sex chromosomes were more frequently confounded by maternal cell contamination and other technical factors.     

Issues arising from the prenatal diagnosis of some rare trisomy mosaics--the importance of cryptic fetal mosaicism

OBJECTIVES: To add to the knowledge of fetal mosaicism, confined placental mosaicism (CPM), and uniparental disomy (UPD), in rare trisomies detected at prenatal diagnosis. METHODS: The origin of rare trisomy mosaics, mostly (8/11) seen in amniocytes, was examined in 11 cases by follow-up karyotyping and the study of microsatellite inheritance. RESULTS: Of the rare trisomies presented, three were mosaic trisomy 16 (two of which were CPM), and the remainder comprised single cases of mosaic trisomies of 8, 9, 10, 11, 12, 14, 5 and 15--the last two being CPM. Cases varied in parental derivation and meiotic versus post-zygotic origin but no case involved UPD. There was evidence for cryptic fetal mosaicism in three cases (5, 7, 11)--involving chromosomes 11, 14 and 16. CONCLUSIONS: These cases contribute further data to phenotypes associated with rare trisomies and the relative influences on the phenotype of CPM, UPD and fetal mosaicism. From sparse published data, we estimate that approximately 10% of apparent CPM cases for a rare trisomy (i.e. aneuploid CVS, normal amniocytes) may actually be cryptic fetal mosaics undetected in cultured amniocytes. In many cases, this cryptic mosaicism may be of limited clinical significance, but in others, the associated phenotypic effects may be obvious. There is no general approach to resolve this issue; the finding of even a few similar aneuploid cells in different amniocyte culture vessels may be clinically significant. It may be useful to study such an amniocyte culture with FISH with the relevant centromeric probe. Careful follow-up is recommended, particularly for infants where apparent correction of autosomal trisomy has occurred.     

A de novo duplication of chromosome 21q22.11→qter associated with Down syndrome: prenatal diagnosis, molecular cytogenetic characterization and fetal ultrasound findings

ObjectivesTo present prenatal diagnosis and molecular cytogenetic characterization of de novo partial partial trisomy 21q (21q22.11 → qter) associated with clinodactyly and hypoplastic midphalanx of the fifth fingers, midface hypoplasia, and an intracardiac echogenic focus on prenatal ultrasound.Materials, Methods, and ResultsA 34-year-old gravida 2, para 1 woman underwent amniocentesis at 20 weeks of gestation because of fetal structural abnormalities on prenatal ultrasound. A level II ultrasound at 20 weeks of gestation showed polyhydramnios, clinodactyly and hypoplastic midphalanx of the fifth fingers, midface hypoplasia, and an intracardiac echogenic focus. Amniocentesis revealed an aberrant derivative chromosome 9, or der(9). Parental karyotypes were normal. Spectral karyotyping (SKY) and fluorescence in situ hybridization (FISH) analyses revealed that the der(9) contained a segment of chromosome 21 distal to chromosome 9q, and FISH analysis additionally showed that the distal subtelomeric region of 9q was not deleted. Array comparative genomic hybridization (aCGH) demonstrated a 14.8-Mb duplication of distal 21q encompassing the Down syndrome critical region (DSCR) but no genomic imbalance in the distal euchromatic region of chromosome 9. The karyotype was 46,XX,der(9)t(9;21) (q34.3;q22.11)dn. Polymorphic DNA marker analysis revealed the maternal origin of the aberrant chromosome. The pregnancy was subsequently terminated. A malformed female fetus was delivered with a characteristic phenotype of Down syndrome.ConclusionSKY, FISH and aCGH are useful in prenatal investigation of the nature of a de novo aberrant derivative chromosome. Partial trisomy 21q encompassing the DSCR may present characteristic Down syndrome features on prenatal ultrasound.     

Cytogenetic analysis of human blastocysts

The human blastocyst is key to understanding the aetiology of constitutional chromosome abnormalities in our species.OBJECTIVES: To investigate the range and incidence of chromosome abnormalities in a large series of human blastocysts, using classic cytogenetic techniques. METHODS: Using thymidine, cell division is synchronized in spare five-to-eight-day-old human blastocysts generated by IVF. A simple acetic acid disaggregation step produces discrete metaphases for G-band analysis. Subsequent FISH analysis of both metaphase and interphase nuclei allows further exploration of an abnormality detected by G-banding, including the investigation of any mosaicism. RESULTS: A total of 438 blastocysts have been prepared. Where analysis was possible, 3% appeared polyploid (mainly tetraploid), 29% were diploid : tetraploid mosaics and 68% were uniformly diploid. Abnormalities observed include triploidy, trisomy 16, trisomy 2, trisomy for unidentifiable D-group chromosome, mosaic trisomy 3, and mosaic trisomy 3 and trisomy 7. CONCLUSION: Comparison of results with existing data from both first trimester pregnancies and cleavage stage embryos suggests significant loss of haploid and monosomic embryos, as well as loss of some trisomies, prior to the blastocyst stage. It appears that the general range and incidence of most main groups of constitutional abnormalities observed in the first trimester (including mosaic forms) are in place by the blastocyst stage.     

Retrospective diagnosis of trisomy 15 in formalin-fixed, paraffin-embedded placental tissue in a newborn girl with Prader-Willi syndrome

Paternal deletion of 15q11-q13 and maternal uniparental disomy (UPD) of chromosome 15 are the main causes of Prader-Willi syndrome (PWS). The finding of an UPD(15) is associated with increased maternal age. We present a retrospective diagnosis of a trisomy 15 mosaicism confined to the placenta (CPM) after birth of a girl with clinical features of PWS born to a 43-year-old mother. Chromosome analysis after amniocentesis, performed because of advanced maternal age, had shown a normal female karyotype. In peripheral blood cells molecular studies showed the absence of the paternal allele at the SNRPN locus and fluorescence in situ hybridization (FISH) analysis excluded a deletion of the SNRPN locus on both chromosomes 15. Trisomic cells were detected by FISH on nuclei isolated from formalin-fixed, paraffin-embedded placental tissue using a DNA-probe specific for the centromeric region of chromosome 15.     

A pregnancy with discordant fetal and placental chromosome 18 aneuploidies revealed by invasive and noninvasive prenatal diagnosis

This study investigated a pregnancy where the fetus was diagnosed with monosomy 18p by invasive amniocentesis and karyotyping. Additional noninvasive prenatal diagnosis, which detects fetal chromosome abnormalities in the circulating cell-free plasma DNA originating from the placenta revealed a related 18p monosomy/18q trisomy, suggesting confined placental mosaicism. Based on recent observations of chromosomal instability in the early preimplantation embryo, this study speculates on the possible embryonic origin(s) of these related but discordant chromosome 18 aneuploidies in the placental and fetal tissues. The findings highlight the potential for both false-positive and -negative noninvasive prenatal diagnosis results in pregnancies where there is either confined placental mosaicism or placental mosaicism.The study investigated a pregnancy involving a fetus with a chromosome disease syndrome called monosomy 18p where part of the short arm of chromosome 18 was missing in the fetal tissues. Using non-invasive prenatal diagnosis which detects fetal chromosome abnormalities in the circulating cell free plasma DNA originating from the placenta, we also detected monosomy 18p as well a related chromosome 18 abnormality involving duplication of the long arm of chromosome 18. This suggested confined placental mosaicism where the constitution of the chromosomes are different between fetal and placental tissues. We speculated that these related chromosome 18 abnormalities arose during preimplantation embryo development, leading to the formation of different chromosome abnormalities observed in the placental and fetal tissues of this pregnancy. Our findings highlight the potential for both false positive and negative non-invasive prenatal diagnosis test results in pregnancies where there is confined placental mosaicism.     

Impact of parental gonosomal mosaicism detected in peripheral blood on preimplantation embryos

This study evaluated the chromosomal condition of embryos generated by patients with an altered karyotype due to gonosomal mosaicism and the clinical outcome after preimplantation genetic diagnosis (PGD) for aneuploidy. Thirty-six patients aged 34.6 +/- 3.6 years performed 54 treatment cycles and had 295 embryos diagnosed by fluorescence in-situ hybridization (FISH). Thirty-seven per cent of the embryos were chromosomally normal and generated 19 clinical pregnancies after replacement in 39 cycles. Only one pregnancy miscarried, yielding a take-home baby rate of 33.3%. Autosomal monosomy and trisomy contributed 36.1% of total abnormalities and gonosomal aneuploidy 5.9%, similar to the results detected in patients who undergo PGD for increased maternal age. Reanalysis was performed on 114 non-transferrable embryos: 41 were found to be mosaics, which were grouped in three different types, chaotic mosaics (56%), aneuploid mosaics (29%) and diploid/haploid/polyploid mosaics (15%). The incidence of aneuploid mosaics was higher than expected compared with PGD patients of the same age and resembled the condition observed in patients of advanced maternal age. These findings suggest that constitutional carriers of sex chromosome mosaicism are predisposed to autosomal mosaicism of embryos, possibly due to errors of cell division. There is an indication that this tendency is higher in female than male carriers.     

Discordant prenatal diagnosis of trisomy 21 due to mosaic structural rearrangements of chromosome 21

OBJECTIVES: Trisomy 21 mosaicism associated with a structural rearrangement of chromosome 21 is uncommon. We report on two prenatal diagnoses in which karyotypes showed mosaicism with an aberrant cell line, including a structural rearrangement of chromosome 21. METHODS: Both these cases were associated with increased nuchal translucency. Conventional and molecular cytogenetic analyses were performed on uncultured and cultured trophoblast and amniotic fluid cells. RESULTS: In Case 1, analysis of trophoblast cells revealed an abnormal karyotype of 47,XX,+mar.ish der(13/21)(D13Z1/D21Z1+)/46,XX. The amniocentesis showed a free non-mosaic trisomy 21. In Case 2, the trophoblast direct analysis showed a normal male karyotype whereas the long-term culture revealed a mosaicism for a dicentric long-arm isochromosome 21: 46,XY,idic(21)(p11)/45,XY,-21/46,XY. Amniocentesis showed an unbalanced non-mosaic karyotype 46,XY,idic(21)(p11) resulting therefore in trisomy for the long arm of chromosome 21. CONCLUSION: Our cases underline the importance of combining the direct analysis and long-term culture of trophoblast and emphasise the need for confirmatory studies in other tissues when mosaicism of structural rearrangement is encountered in chorionic villi. The meiotic and mitotic mechanisms of formation of these structural rearrangements of chromosome 21 are discussed.     

Two cases of confined placental mosaicism for chromosome 4, including one with maternal uniparental disomy

Two cases of trisomy 4 mosaicism are reported including one with molecularly confirmed uniparental disomy (UPD) of chromosome 4. Cytogenetic analysis of a chorionic villus sample (CVS) in Case 1 showed complete trisomy 4 in trophoblast and diploidy in chorionic stroma. Amniotic fluid analysis demonstrated a 46,XX complement. After intrauterine fetal death at 30 weeks, molecular analysis confirmed the presence of trisomy 4 of maternal meiotic origin, while fetal tissues showed maternal UPD for chromosome 4. Cultured CVS in Case 2 revealed trisomy 4 in 2/30 cells analyzed. This pregnancy resulted in a healthy livebirth with biparental inheritance of chromosome 4. Molecularly confirmed UPD4 has not been previously reported, and therefore, although the adverse outcome in Case 1 is likely due to the trisomy 4 in the placenta, an imprinting effect associated with UPD4 cannot be excluded.