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

Contribution of uniparental disomy to fetal growth restriction: a whole-exome sequencing series in a prenatal setting

Fetal growth restriction (FGR), a leading cause of perinatal morbidity and mortality, is caused by fetal, maternal, and placental factors. Uniparental disomy (UPD) is a rare condition that leads to imprinting effects, low-level mosaic aneuploidies and homozygosity for pathogenic variants. In the present study, UPD events were detected in 5 women with FGR by trio exome sequencing (trio-WES) of a cohort of 150 FGR cases. Furthermore, noninvasive prenatal testing results of the 5 patients revealed a high risk of rare autosomal trisomy. Trio-WES showed no copy-number variations (CNVs) or nondisease-causing mutations associated with FGR. Among the 5 women with FGR, two showed gene imprinting, and two exhibited confined placental mosaicism (CPM) by copy number variant sequencing (CNV-seq). The present study showed that in FGR patients with UPD, the detection of imprinted genes and CPM could enhance the genetic diagnosis of FGR.

Pregnancy outcome of confined placental mosaicism: meta-analysis of cohort studies

OBJECTIVE

This study aimed to assess the rate of adverse obstetrical and neonatal outcomes in pregnancies diagnosed with confined placental mosaicism relative to that of unaffected controls.

DATA SOURCES

Web-based databases were searched using relevant key words, and articles published from 1980 to February 2022 were retrieved.

STUDY ELIGIBILITY CRITERIA

Observational studies in English language including ≥10 cases of singleton pregnancies with diagnosis of confined placental mosaicism were included. The diagnosis was established after detection of any chromosomal abnormality at chorionic villus sampling for any indication, followed by normal karyotype from amniotic fluid or neonatal leukocyte culture.

METHODS

Two authors independently screened the references for eligibility, data extraction, and assessment of methodological quality using the Newcastle-Ottawa scale. All available obstetrical and neonatal outcomes were recorded. Random-effect meta-analysis was performed to estimate pooled odds ratios and 95% confidence intervals of available outcomes in pregnancies with and without confined placental mosaicism. Statistical heterogeneity was evaluated with I2 statistics (International Prospective Register of Systematic Reviews registration number: CRD42021260319).

RESULTS

Of the 80 articles reviewed, 8 retrospective matched-cohort studies (708 cases of confined placental mosaicism and 11,599 unaffected controls) compared cases with and without confined placental mosaicism and were included in the meta-analysis. The risk of delivering small-for-gestational-age neonates was significantly increased in confined placental mosaicism pregnancies according to crude analysis (odds ratio, 2.45; 95% confidence interval, 1.23-4.89; I2=72%) and to sensitivity analysis of high-quality studies (odds ratio, 3.65; 95% confidence interval, 2.43-5.57; I2=0%). Similarly, confined placental mosaicism resulted in an increased risk of birthweight below the third centile (odds ratio, 5.33; 95% confidence interval, 1.19-24.19; I2= 83%). Subgroup analysis revealed that the risk of delivering small-for-gestational-age neonates was 3-fold higher for confined placental mosaicism excluding trisomy 16, and 11-fold higher for cases including trisomy 16 only vs unaffected controls, respectively. No difference was found in the risk of low birthweight and preterm birth (at <37 weeks' gestation). Other outcomes were insufficiently reported, therefore they were not analyzed.

CONCLUSION

Pregnant women prenatally diagnosed with confined placental mosaicism have an increased risk of impaired fetal growth, suggesting the need for intensified antenatal surveillance.

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.

Pregnancy outcome of autosomal aneuploidies other than common trisomies detected by noninvasive prenatal testing in routine clinical practice

OBJECTIVE

The objective of the study is to report the incidence and pregnancy outcome of autosomal aneuploidies other than common trisomies 21, 18, and 13 detected by noninvasive prenatal testing (NIPT) at a single center.

METHODS

Pregnant women undergoing NIPT from February 2015 to January 2018 in our center were offered expanded screening to include rare autosomal aneuploidies. Aneuploidies included extra copy chromosomes (most likely trisomies) and decreased copy chromosomes (most likely monosomies). The pregnancy outcomes of women consenting to the expanded NIPT screen were recorded.

RESULTS

Expanded NIPT was performed in 15 362 pregnancies. A total of 59 autosomal aneuploidies other than the 3 common trisomies were detected, with a positive screening rate of 0.38% (59/15 362). The screen positive rate was higher in women aged above 35 years than in those younger (0.44% vs 0.32%, P < .05). Of the screen positive results, 30.5% (18/59) were because of extra copies for chromosomes trisomy 7, 10.2% (6/59) for chromosome 22, and 8.5% (5/59) for chromosomes 8 and 16 respectively, while other choromosomes were less frequently involved. Decreased copy chromosomes were less common: 6.8% (4/59) for chromosomes 14 and 13. Mixed aneuploidies with increased copies for some chromosomes and decreased copies for others were also noted. Invasive prenatal diagnosis was performed in 61% (36/59) of the cases. Invasive test results and clinical follow-ups demonstrated that most (94.9%, 56/59) of the rare aneuploidies were false positives, probably resulting from confined placental mosaicism. Only 1 case (1.7%, 1/59) with NIPT report of extra copies of chromosome 7 and without ultrasound evidence of fetal abnormality was confirmed to be fetal mosaicism by microarray test. Uniparental disomy of whole chromosome 2 was identified by microarray analysis in 1 case with extra copy chromosome 2 detected by NIPT. Loss of heterozygocity of chromosome 7q11.23-q21.11 was detected in another case with extra copy chromosome 7. Fortunately, pregnancy outcomes of both cases were normal. Two fetal deaths attributed to severe fetal growth restriction were associated with extra copies of chromosome 16 at expanded NIPT.

CONCLUSIONS

Autosomal aneuploidies other than trisomies 21, 18, and 13 are not uncommon in routine clinical NIPT practice. Extra copies of chromosomes in rare cases can be associated with uniparental disomy. Most rare aneuploidies at NIPT have good pregnancy outcomes. Thus, invasive testing should be used with caution for these aneuploidies in routine clinical practice.

Factors that affect maternal insulin resistance and modify fetal growth and body composition

Fetal growth is multifactorial and can be altered by a variety of extrinsic and intrinsic factors. The maternal, placental, and fetal contribution to growth must all be considered. Of particular interest are maternal metabolic regulation and the availability of nutrients to the developing fetus. Weight gain, hyperlipidemia, and insulin resistance occur as a normal adaptation to pregnancy. Obesity and underlying insulin resistance among women of reproductive age are rapidly increasing, and the contribution of pregnancy on this abnormal metabolic background poses additional maternal and fetal challenges. Many components of the metabolic syndrome have been associated with changes in fetal growth, including obesity, dyslipidemia, hypertension, and insulin resistance or glucose intolerance. Additional factors affect fetal growth and include diet, exercise, and smoking. In this review, we briefly discuss the importance and descriptions of fetal growth, followed by a discussion of several of the extrinsic and intrinsic established factors affecting fetal growth. We highlight factors that may modify fetal growth and body composition directly or indirectly through alterations in maternal metabolism.

Genome-wide detection of uniparental disomy in a fetus with intrauterine growth restriction using genotyping microarrays

OBJECTIVE

To present the clinical and molecular features of a fetus with confined trisomy 16 mosaicism with maternal uniparental disomy (UPD), using various prenatal diagnostic techniques.

MATERIALS AND METHODS

Chromosomal karyotyping was performed on samples of chorionic villi, amniotic fluid cells, amniotic membrane, umbilical cord, fetal skin, and placenta from a fetus with elevated nuchal translucency. Polymorphic short tandem repeat markers and Affymetrix single nucleotide polymorphism (SNP) mapping chips were used for molecular analyses.

RESULTS

Karyotypes from chorionic villi and amniocytes showed 47,XX,+16 and 46,XX, respectively. Short tandem repeat markers on chromosome 16 suggested maternal UPD for chromosome 16. Affymetrix 10K SNP mapping chips were used to simultaneously confirm the difference in karyotypes between the placenta and amniocytes and to diagnose UPD for chromosome 16. Fetal ultrasonography and magnetic resonance imaging identified severe intrauterine growth restriction (IUGR). Autopsy revealed IUGR, incomplete lobulation of bilateral lungs, and malrotation of the intestines. The karyotypes of umbilical cord, fetal skin and amniotic membrane were 46,XX, and the trisomy 16 karyotype appeared to be confined to the placenta.

CONCLUSION

UPD should be investigated as a possible etiology in all cases of unexplained IUGR. SNP microarrays can be useful for confirming this diagnosis.

Lack of aneuploidy for chromosomes 15, 16, and 18 in placentas from small-for-gestational-age liveborn infants

OBJECTIVE

The purpose of this study was to investigate the frequency of confined placental mosaicism (CPM) in placentas from liveborn infants.

STUDY DESIGN

A retrospective analysis of 51 placentas from small-for-gestational-age (SGA), live born infants (birthweight below 5th centile), and 45 placentas from normally grown infants at term was performed. Aneuploidy for chromosomes 15, 16, and 18 was analyzed with QF-PCR (polymorphic markers) and FISH (centromeric probes).

RESULTS

No trisomic sample was detected with either method. FISH revealed 1 case of monosomy 16 in the SGA group, which was not confirmed by PCR. On the other hand, PCR analysis showed allelic imbalances, ie, deviation of the 1:1 peak ratio > 20%, in 5 cases (4 in the SGA and 1 in the control group; P = .157).

CONCLUSION

Trisomic CPM in liveborn SGA infants is much less frequent than previously appreciated. The occurrence and eventual biologic significance of the observed allelic imbalances needs to be further investigated.

Subtelomeric rearrangements and 22q11.2 deletion syndrome in anomalous growth-restricted fetuses with normal or balanced G-banded karyotype

OBJECTIVE

To determine the frequencies of cryptic subtelomeric rearrangements and 22q11.2 deletion in anomalous growth-restricted fetuses with normal or balanced G-banded karyotypes.

METHODS

This was a study of 27 consecutive fetuses at a median gestational age of 26 (range, 19-33) weeks, that had intrauterine growth restriction (IUGR) as well as at least one major structural anomaly, and a normal or balanced G-banded karyotype. The median maternal age was 29 (range, 17-39) years. Fluorescence z in-situ hybridization (FISH) diagnosis of the cultured amniocytes with the probe TUPLE 1, and then the Chromoprobe Multiprobe-T system were used, respectively, to screen for the frequency of 22q11.2 deletion syndrome and subtelomeric rearrangements involving the 41 unique chromosome ends (i.e. excluding the five short arms of acrocentric autosomes (no. 13, 14, 15, 21 and 22)). Those that had suspected deleted subtelomeres were reanalyzed with a specific subtelomeric probe, TelVysion.

RESULTS

Of the 27 fetuses, three (11%) were affected with 22q11.2 deletion syndrome and two (7.4%) had subtelomeric deletions (one monosomy 21q22.3, one monosomy 1p36.3). Of the 11 fetuses with congenital heart defects, three (27.3%) had 22q11.2 deletion syndrome and one (9.1%) had monosomy 1p36.3. In the remaining 16 fetuses without congenital heart defects, none had 22q11.2 deletion syndrome. However, one (6.3%) had cryptic rearrangement involving subtelomeres.

CONCLUSION

Prenatal subtelomeric FISH screening is technically feasible using cultured amniocytes. We propose that 22q11.2 deletion syndrome and cryptic subtelomere rearrangements may be important etiologies of fetuses with IUGR and at least one structural anomaly, along with a normal karyotype or one that is balanced by traditional G-banding. Fetuses with congenital heart defects and IUGR should undergo FISH to exclude 22q11.2 deletion syndrome. In fetuses with IUGR and at least one major structural anomaly but without congenital heart defects, screening of subtelomeric rearrangements may contribute to further elucidation of the underlying etiology.

A novel heterozygous missense mutation 377T > C (V126A) ofTGIF gene in a family segregated with holoprosencephaly and moyamoya disease

OBJECTIVES

To identify whether any mutations of candidate genes including SHH, ZIC2, SIX3, and TGIF exist in a Taiwanese family segregated with holoprosencephaly (HPE) and moyamoya disease.

METHODS

Genotypes of the candidate genes SHH, ZIC2, SIX3, and TGIF were determined in the family members who were available for analysis by sequencing. In addition, genomic regions of another 50 unrelated Taiwanese (100 chromosomes) were studied to verify whether the nucleotide changes we found were mutations or polymorphisms.

RESULTS

A novel missense mutation 377T > C and two polymorphisms (420A > G and 487C > T) in the TGIF gene were identified. No mutations in SHH, ZIC2 and SIX3 were found. The mother of the three HPE fetuses was found to be afflicted with moyamoya disease. A brief review of the mutations as well as polymorphisms reported in the TGIF gene up to 2005 is given.

CONCLUSION

Molecular diagnosis can help genetic counseling in HPE, which is a heterogeneous disorder with its phenotypic and genotypic spectrum highly widened and variable. The possible association between TGIF mutation and moyamoya disease noted in our study also appeared to be novel.

Trisomy 15 mosaicism owing to familial reciprocal translocation t(1;15): implication for prenatal diagnosis

We describe a 4-year-old female child with severe global mental retardation, myoclonic epilepsy, proximal hypotonia and dysmorphisms, whose prenatal diagnosis following amniocentesis revealed a constitutional female karyotype carrying a t(1;15)(q10;p11) familial reciprocal translocation. Post-natal high-resolution karyotype, Fluorescence in situ hybridization (FISH) screening for subtelomeric rearrangements, VNTR search for UPD15 in the blood and fibroblast, and WCP1 and 15 in the mother, failed to provide an explanation for the complex clinical phenotype of the proband. Since the pachytene configuration of the translocated chromosomes defines a high probability of 3:1 segregation, an extensive workup was undertaken to look for a possibly cryptic mosaicism. Four percent of the cells with trisomy 15 was found in the peripheral blood lymphocytes examined by classical cytogenetic technique and interphase FISH analysis. The clinical features associated with cryptic trisomy 15 mosaicism and the problems concerning prenatal diagnosis and genetic counselling for carriers of translocations at high risk of 3:1 segregation are discussed.