Severe fetal malformations associated with trisomy 16 confined to the placenta

Confined placental mosaicism and the association with pregnancy outcome and fetal growth: a review of the literature

BACKGROUND

Chromosomal mosaicism can be detected in different stages of early life: in cleavage stage embryos, in blastocysts and biopsied cells from blastocysts during preimplantation genetic testing for aneuploidies (PGT-A) and later during prenatal testing, as well as after birth in cord blood. Mosaicism at all different stages can be associated with adverse pregnancy outcomes. There is an onward discussion about whether blastocysts diagnosed as chromosomally mosaic by PGT-A should be considered safe for transfer. An accurate diagnosis of mosaicism remains technically challenging and the fate of abnormal cells within an embryo remains largely unknown. However, if aneuploid cells persist in the extraembryonic tissues, they can give rise to confined placental mosaicism (CPM). Non-invasive prenatal testing (NIPT) uses cell-free (cf) DNA released from the placenta in maternal blood, facilitating the detection of CPM. In literature, conflicting evidence is found about whether CPM is associated with fetal growth restriction (FGR) and/or other pregnancy outcomes. This makes counselling for patients by clinicians challenging and more knowledge is needed for clinical decision and policy making.

OBJECTIVE AND RATIONALE

The objective of this review is to evaluate the association between CPM and prenatal growth and adverse pregnancy outcomes. All relevant literature has been reviewed in order to achieve an overview on merged results exploring the relation between CPM and FGR and other adverse pregnancy outcomes.

SEARCH METHODS

The following Medical Subject Headings (MESH) terms and all their synonyms were used: placental, trophoblast, cytotrophoblast, mosaicism, trisomy, fetal growth, birth weight, small for gestational age and fetal development. A search in Embase, PubMed, Medline Ovid, Web of Science, Cochrane Central Register of Controlled Trials (CENTRAL) and Google Scholar databases was conducted. Relevant articles published until 16 July 2020 were critically analyzed and discussed.

OUTCOMES

There were 823 articles found and screened based on their title/abstract. From these, 213 articles were selected and full text versions were obtained for a second selection, after which 70 publications were included and 328 cases (fetuses) were analyzed. For CPM in eight different chromosomes (of the total 14 analyzed), there was sufficient evidence that birth weight was often below the 5th percentile of fetal growth standards. FGR was reported in 71.7% of CPM cases and preterm birth (<37 weeks of delivery) was reported in 31.0% of cases. A high rate of structural fetal anomalies, 24.2%, in cases with CPM was also identified. High levels of mosaicism in CVS and presence of uniparental disomy (UPD) were significantly associated with adverse pregnancy outcomes.

WIDER IMPLICATIONS

Based on the literature, the advice to clinicians is to monitor fetal growth intensively from first trimester onwards in case of CPM, especially when chromosome 2, 3, 7, 13, 15, 16 and 22 are involved. In addition to this, it is advised to examine the fetuses thoroughly for structural fetal anomalies and raise awareness of a higher chance of (possibly extreme) premature birth. Despite prematurity in nearly a fifth of cases, the long-term follow-up of CPM life borns seems to be positive. More understanding of the biological mechanisms behind CPM will help in prioritizing embryos for transfer after the detection of mosaicism in embryos through PGT-A.

Vesicules or placental lakes in ultrasonography, determining the correct etiology

The prenatal examination of the placenta is often an afterthought to that of the fetus in ultrasonography. Not giving the placenta its due may however result in potentially serious placental pathologies remaining undiscovered, notably in the presence of anechoic zones. These latter have earned numerous names, including "placental lakes", "placental venous lakes", "placental lacunae" or "placental caverns" among others, but they have received little attention in the literature. We thus feel that it is essential to review the various pathologies that placental lakes may signal, since any one of them may greatly affect patient management. The difficulty resides in the diversity of these pathologies, sometimes oncological, other times fetal, and in the potential need for multidisciplinary surgery. Some of these causes of placental lakes may result in maternal or fetal complications and/or necessitate increased and casespecific surveillance. The diagnosis and treatment of such cases requires close collaboration between sonographers, obstetricians, geneticists and pathologists. The work we present here focuses on the different etiologies to consider in the presence of a lacunar placenta and the necessary diagnostic measures. Our objective is to propose a diagnostic flowchart to aid clinicians in this dense differential diagnosis.

Prognosis for pregnancies with trisomy 16 confined to the placenta: A Danish cohort study

OBJECTIVE

To evaluate the risk of adverse pregnancy outcome when trisomy 16 confined to the placenta is diagnosed and to identify possible prognostic markers for adverse outcomes in these pregnancies.

METHOD

Registered cases (n = 49) of trisomy 16 diagnosed prenatally in Denmark from 1990 to 2013 were included.

RESULTS

Twenty-five of the pregnancies intended to be continued had confined placental trisomy 16 mosaicism (CPM16). Adverse pregnancy outcome was seen in 17 CPM16 pregnancies (68%), ranging from mild small for gestational age (SGA) to fetal malformations and intrauterine demise. For cases ascertained by combined first trimester screening, the median concentration of pregnancy associated plasma protein A (PAPP-A) was 0.17 MoM (IQR: 0.11 MoM). Adverse pregnancy outcome showed a trend toward an association with a high frequency of trisomic cells. Eight children (32%) were born at term with a normal birth weight and no malformations.

CONCLUSION

The risk of adverse pregnancy outcome in case of CPM16 is correlated to ascertainment by combined first trimester screening and tends to be associated with a high frequency of trisomic cells in the placenta. We recommend that variables including ascertainment, the frequency of trisomic cells, and the maternal serum concentration of PAPP-A are taken into consideration when evaluating the prognosis in CPM16 while acknowledging that these factors are strongly correlated.

Novel parent-of-origin-specific differentially methylated loci on chromosome 16

BACKGROUND

Congenital malformations associated with maternal uniparental disomy of chromosome 16, upd(16)mat, resemble those observed in newborns with the lethal developmental lung disease, alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV). Interestingly, ACDMPV-causative deletions, involving FOXF1 or its lung-specific upstream enhancer at 16q24.1, arise almost exclusively on the maternally inherited chromosome 16. Given the phenotypic similarities between upd(16)mat and ACDMPV, together with parental allelic bias in ACDMPV, we hypothesized that there may be unknown imprinted loci mapping to chromosome 16 that become functionally unmasked by chromosomal structural variants.

RESULTS

To identify parent-of-origin biased DNA methylation, we performed high-resolution bisulfite sequencing of chromosome 16 on peripheral blood and cultured skin fibroblasts from individuals with maternal or paternal upd(16) as well as lung tissue from patients with ACDMPV-causative 16q24.1 deletions and a normal control. We identified 22 differentially methylated regions (DMRs) with ≥ 5 consecutive CpG methylation sites and varying tissue-specificity, including the known DMRs associated with the established imprinted gene ZNF597 and DMRs supporting maternal methylation of PRR25, thought to be paternally expressed in lymphoblastoid cells. Lastly, we found evidence of paternal methylation on 16q24.1 near LINC01082 mapping to the FOXF1 enhancer.

CONCLUSIONS

Using high-resolution bisulfite sequencing to evaluate DNA methylation across chromosome 16, we found evidence for novel candidate imprinted loci on chromosome 16 that would not be evident in array-based assays and could contribute to the birth defects observed in patients with upd(16)mat or in ACDMPV.

Mosaic trisomy 16: what are the obstetric and long-term childhood outcomes?

PURPOSE

To evaluate obstetric and neonatal outcomes as well as long-term neurodevelopmental outcomes and quality of life among prenatally detected cases of mosaic trisomy (MT16) and confined placental mosaicism (CPM) for trisomy 16.

METHODS

We recruited participants for this cross-sectional study through an international registry of families with children diagnosed with MT16 or CPM. Parents were interviewed about expectations based on prenatal counseling as well as about actual perinatal outcomes, congenital anomalies, medical conditions, and school progress. Health-related quality of life (HRQOL) was assessed via the Pediatric Quality of Life Inventory 4.0 Generic Core Scales.

RESULTS

Forty-four families were enrolled, and 68.2% of the children were female. Common complications were gestational hypertension (gHTN) or preeclampsia (38.1%), preterm delivery (PTD; 71.4%), cesarean delivery (CD; 73.8%), birth weight <10th percentile (73.8%), neonatal intensive care unit (NICU) admission (88.1%), and congenital anomalies (59.5%). However, 81.8% of school-aged children were entirely in mainstream classes, and median physical, psychosocial, and total HRQOL scores were high: 90.6 (34.4-100), 86.7 (35-100), and 84.8 (34.8-100), respectively (100 = optimal quality of life).

CONCLUSION

Several obstetric and neonatal complications are common with pregnancies affected by MT16 or CPM. However, the majority of children demonstrate normal neurodevelopmental outcomes and high HRQOL.Genet Med advance online publication 06 April 2017.

Intrauterine growth retardation fetus with trisomy 16 mosaicism

Fetal trisomy 16 is considered uniformly lethal early in gestation. It has been reported to be associated with the variability of clinical features and outcomes. Mosaic trisomy 16 leads to a high risk of abnormality in prenatal cases. Intrauterine growth retardation (IUGR) is a common outcome of mosaic trisomy 16. Herein, we report on the case of Thai male IUGR fetus with trisomy 16 mosaicism. The fetal body was too small. Postmortem investigation of placenta revealed the abnormality including small placenta with furcated cord insertion and single umbilical cord artery. Cytogenetic study demonstrated trisomy 16 that was found 100% in placenta and only 16% in the fetal heart while other organs had normal karyotype. In addition, cardiac and other internal organs examination revealed normal morphology.

Non-mosaic uniparental trisomy 16 presenting with asplenia syndrome and placental abruption: a case report and literature review

Non-mosaic trisomy 16 is rarely seen in later gestation. Herein, we report a fetus with uniparental complete trisomy 16 manifesting with asplenia syndrome, left hand deformity (only 3 deformed fingers on the left hand) and a left low-set ear. The pregnancy ended in severe placental abruption and resultant fetal demise, and maternal hypovolemic shock at 35 weeks of gestation. Only 3 non-mosaic trisomy 16 fetuses, including this case, have been reported to survive into the second or third trimester. Furthermore, this fetus would be the first case of complete trisomy 16 manifesting as asplenia syndrome.

Prenatal diagnosis of trisomy 16 mosaicism manifested as pulmonary artery stenosis

Trisomy 16 mosaicism detected at midtrimester amniocentesis is rare and indicative of true fetal mosaicism. We report a case of mosaic trisomy 16 diagnosed by amniocentesis in which the sonographic findings included fetal pulmonary artery stenosis, a single umbilical artery, and early onset fetal growth restriction. The pregnancy was legally terminated. A review of previous reports suggests that abnormalities of outlet tracts are rarely encountered in fetuses with trisomy 16 mosaicism revealed via amniocentesis.

Abnormal abdominal situs: what and how should we look for?

BACKGROUND

Prenatal management of abnormal abdominal situs is challenging since prognosis is highly variable depending on the associated malformations.

METHODS

The authors report on two cases of ambiguous abdominal situs. Prenatal management included specialized ultrasound examination of fetal anatomy and heart, amniocentesis for determination of the fetal karyotype and fetal abdominal MR.

RESULTS

In both cases, abnormal situs was associated with other abdominal anomalies such as azygous continuation, biliary atresia, bowel obstruction and polysplenia. Fetal MR was a useful additional tool in the assessment of fetal abdominal anatomy in both cases.

CONCLUSIONS

On the basis of these reports, the literature is reviewed and a prenatal management scheme is proposed.

Variable outcomes in mosaic trisomy 16: five case reports and literature analysis

OBJECTIVES

To report five cases of mosaic trisomy 16 with variable outcomes in the context of the literature on mosaic trisomy 16. Complications in these cases include preeclampsia, IUGR, fetal anomalies, and death, with no predictable pattern.

METHODS

Observation of five new cases and statistical analysis of 125 reported cases of mosaic trisomy 16 with prenatal detection and outcome data.

RESULTS

(1) IUGR, premature delivery, and/or physical anomalies are observed commonly, even when the trisomy is thought to be confined to the placenta; (2) Level II mosaicism for trisomy 16 in amniotic fluid may reflect a true mosaic state with phenotypic consequences; (3) FISH is more sensitive than traditional cytogenetics in detecting mosaicism in all tissue types examined; (4) hCG levels can be extremely elevated, and MS-AFP levels are often elevated; and (5) Uniparental disomy (UPD) increases the rates of IUGR and physical anomalies in CPM cases.

CONCLUSION

While there is no obvious mosaic trisomy 16 syndrome, IUGR and heart defects commonly occur, even if the mosaicism appears to be confined to the placenta. A completely normal outcome occurs only in about 20% of the cases; however, complications can often be limited to prematurity, small-for-gestational-age infants, and/or minor or surgically reparable birth defects.

Imprinted genes and their role in human fetal growth

Growth is defined as the progressive increase in size and is listed as one of the eight main characteristics of life. In human gestation the most rapid growth phase is from 16 to 32 weeks when first there is both cell number and size increase and then from 32 weeks onwards there is continued size increase (Pollack and Divon, 1992). The mechanism of growth in utero is of fundamental interest to clinicians and scientists because of its implications for neonatal health. Growth is multifactorial in origin with both genetics and environment contributing equally large parts. Despite this complexity analysis of the candidate genes involved is possible using simple tissue biopsies at the relevant stages of development. Of particular interest in understanding fetal growth is the analysis of a group of genes that show a parent-of-origin effect known as genomic imprinting. Imprinted genes are not only found in eutherian (placental) and metatherian (marsupial) mammals but surprisingly also in plants. Nevertheless, their evolution in mammals appears to be linked primarily to placentation. It is thought to result from a potential conflict between the parents in terms of the drive to successfully propagate their own separate genes and the mother's added drive for her survival through the pregnancy to reproduce again. This means that the mother wants to restrict fetal growth and the father to enhance it.

Mosaic trisomy 16 in a fetus: the complex relationship between phenotype and genetic mechanisms

OBJECTIVES

This study was undertaken to discuss the workup of trisomy 16 pregnancies.

STUDY DESIGN

This case study reports the prenatal detection and postnatal confirmation of mosaic trisomy 16, associated with uniparental disomy (UPD) 16, in a 34-year-old woman who showed elevated maternal serum alpha-fetoprotein and beta-HCG at a gestational age (GA) of 15.5 weeks.

RESULTS

Amniotic fluid (AF) karyotyping at different GAs revealed various levels of trisomy 16 mosaicism (0 to level III). UPD studies at 21 weeks of gestation revealed maternal heterodisomy 16. Serial fetal ultrasonography showed fetal abnormalities: intrauterine growth restriction (IUGR), dilated digestive tract, and gallbladder agenesis. Postmortem examination confirmed the prenatal findings and revealed additional anomalies, such as hypoplastic cerebellum with abnormal gyration of the vermis.

CONCLUSIONS

Workup following prenatal detection of trisomy 16 mosaicism in chorionic villi must include AF karyotyping and serial ultrasound examination of the fetus in order to approach postnatal developmental prognosis.

Heterotaxy syndrome -- asplenia and polysplenia as indicators of visceral malposition and complex congenital heart disease

Heterotaxy results from failure of the developing embryo to establish normal left-right asymmetry. Typical manifestations include abnormal symmetry and malposition of the thoraco-abdominal organs and vessels, complex congenital heart disease and extracardiac defects involving midline-associated structures. The spleen is almost always affected, and there is syndromic clustering of the malformations corresponding to the type of splenic abnormality present. This review outlines the embryologic and genetic background of the heterotaxy syndrome as well as the characteristic anatomic features, clinical manifestations, and diagnostic clues of its two main presentations with asplenia or polysplenia.

Combined pentalogy of Cantrell with tetralogy of Fallot, gallbladder agenesis, and polysplenia: a case report

A male newborn with pentalogy of Cantrell, tetralogy of Fallot, agenesis of the gallbladder, and polysplenia died at 3 days of age. Polysplenia was not previously reported in this association.

Evidence for imprinting on chromosome 16: The effect of uniparental disomy on the outcome of mosaic trisomy 16 pregnancies

Although a number of infants with maternal uniparental disomy of chromosome 16 (upd(16)mat) have been reported, the evidence for imprinting on chromosome 16 is not yet conclusive. To test the hypothesis that upd(16)mat has a distinct phenotype, which would support the existence of imprinted gene(s) on chromosome 16, statistical analysis was performed on a large series (n = 83) of mosaic trisomy 16 cases with molecular determination of uniparental disomy status. The incidence of upd(16)mat was 40%, which is consistent with the expected one third from random chromosome loss during trisomy rescue (P = 0.262). In pairwise comparisons, upd(16)mat was found to be associated with fetal growth restriction (P = 0.029) and with increased risk of major malformation (RR = 1.43; P = 0.053). Regression modeling showed that the effect of upd(16)mat on fetal/neonatal weight and malformation is independent of the degree of trisomy detected in the fetus. Regression modeling to control for the degree of trisomy detected in the placenta was not possible due to limited sample size. We conclude that upd(16)mat is associated with more severe growth restriction, and possibly, with higher risk of malformation. Our hypothesis is that imprinted gene(s) exist on chromosome 16 and that abnormal expression of these gene(s) in upd(16)mat cells during development results in decreased cell proliferation. Although we do not advocate prenatal testing for upd(16), studies on the long-term outcome of upd(16)mat neonates is necessary for counseling purposes.

Polysplenia and situs inversus in siblings. Case reports

Heterotaxy syndromes, otherwise laterality defects, are variations from anatomic left-right asymmetry. Situs inversus is the complete reversal of the normal situs, still situs ambiguus is the randomisation of the normal organ position. Situs ambiguus may be manifested as asplenia or polysplenia syndrome. Normal situs and both types of the heterotaxy syndromes may appear among some affected families, whereas the different situs are rarely expressed in the same family. We describe an autosomal-recessive inherited familial heterotaxy syndrome with two affected siblings - one of whom has situs inversus, and the other with polysplenia syndrome. The polysplenia syndrome was diagnosed by fetal echocardiography. Since the chromosomal or molecular diagnosis of laterality defects are accessible only in X-linked heterotaxy syndromes, the fetal echocardiography is the earliest available diagnostic method in this field. Therefore, fetal echocardiography has great importance for affected families.

Genetic control of intra-uterine growth

The expression of a few genes in the human genome depends on whether they are located on the maternal or on the paternal chromosome. This phenomenon is called genomic imprinting. Several of these genes have a role in normal embryonic and fetal growth, as indicated by an abnormal development associated with disturbed genomic imprinting. This has lead to the suggestion that the genomic imprinting has evolved as a mechanism to regulate embryonic and fetal growth.

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.