Abstract：
OBJECTIVE: To carry out genetic analysis for a fetus with confined placental mosaicism (CPM) for trisomy 2 (T2) in conjunct with fetal uniparental disomy (UPD).
METHODS: Amniocentesis and chromosomal karyotyping was carried out for a pregnant woman with a high risk for chromosome 2 anomalies indicated by non-invasive prenatal testing (NIPT). Single nucleotide polymorphism array (SNP-array) and trio-whole exome sequencing (Trio-WES) were carried out. Ultrasonography was used to closely monitor the fetal growth. Multifocal sampling of the placenta was performed after delivery for copy number variation sequencing (CNV-seq).
RESULTS: The fetus was found to have a normal chromosomal karyotype. SNP-array has revealed multiple regions with loss of heterozygosity (LOH) on chromosome 2. Trio-WES confirmed the presence of maternal UPD for chromosome 2. Ultrasonography has revealed intrauterine growth restriction and oligohydramnios. Intrauterine fetal demise had occurred at 23+4 weeks of gestation. Pathological examination had failed to find salient visceral abnormality. The placenta was proved to contain complete T2 by CNV-seq.
CONCLUSIONS: T2 CPM can cause false positive result for NIPT and may be complicated with fetal UPD, leading to adverse obstetric outcomes such as intrauterine growth restriction, oligohydramnios and intrauterine fetal demise.
METHODS: Amniocentesis and chromosomal karyotyping was carried out for a pregnant woman with a high risk for chromosome 2 anomalies indicated by non-invasive prenatal testing (NIPT). Single nucleotide polymorphism array (SNP-array) and trio-whole exome sequencing (Trio-WES) were carried out. Ultrasonography was used to closely monitor the fetal growth. Multifocal sampling of the placenta was performed after delivery for copy number variation sequencing (CNV-seq).
RESULTS: The fetus was found to have a normal chromosomal karyotype. SNP-array has revealed multiple regions with loss of heterozygosity (LOH) on chromosome 2. Trio-WES confirmed the presence of maternal UPD for chromosome 2. Ultrasonography has revealed intrauterine growth restriction and oligohydramnios. Intrauterine fetal demise had occurred at 23+4 weeks of gestation. Pathological examination had failed to find salient visceral abnormality. The placenta was proved to contain complete T2 by CNV-seq.
CONCLUSIONS: T2 CPM can cause false positive result for NIPT and may be complicated with fetal UPD, leading to adverse obstetric outcomes such as intrauterine growth restriction, oligohydramnios and intrauterine fetal demise.
摘要：
目的：对胎儿2型三体性（T2）结合胎儿单亲体性（UPD）的局限性胎盘镶嵌（CPM）胎儿进行遗传分析。
方法：对无创性产前检测（NIPT）提示2号染色体异常高风险的孕妇进行羊膜穿刺术和染色体核型分析。进行了单核苷酸多态性阵列（SNP-array）和三全外显子组测序（Trio-WES）。超声检查用于密切监测胎儿生长。分娩后进行胎盘的多焦取样以进行拷贝数变异测序(CNV-seq)。
结果：胎儿染色体核型正常。SNP阵列显示2号染色体上有多个杂合性缺失(LOH)的区域。Trio-WES证实了2号染色体的母体UPD的存在。超声检查显示宫内生长受限和羊水过少。宫内胎儿死亡发生在妊娠23+4周。病理检查未能发现明显的内脏异常。通过CNV-seq证明胎盘含有完整的T2。
结论：T2CPM可导致NIPT假阳性结果，并可能并发胎儿UPD，导致不良产科结局，如宫内生长受限，羊水过少和胎儿宫内死亡。
方法：对无创性产前检测（NIPT）提示2号染色体异常高风险的孕妇进行羊膜穿刺术和染色体核型分析。进行了单核苷酸多态性阵列（SNP-array）和三全外显子组测序（Trio-WES）。超声检查用于密切监测胎儿生长。分娩后进行胎盘的多焦取样以进行拷贝数变异测序(CNV-seq)。
结果：胎儿染色体核型正常。SNP阵列显示2号染色体上有多个杂合性缺失(LOH)的区域。Trio-WES证实了2号染色体的母体UPD的存在。超声检查显示宫内生长受限和羊水过少。宫内胎儿死亡发生在妊娠23+4周。病理检查未能发现明显的内脏异常。通过CNV-seq证明胎盘含有完整的T2。
结论：T2CPM可导致NIPT假阳性结果，并可能并发胎儿UPD，导致不良产科结局，如宫内生长受限，羊水过少和胎儿宫内死亡。
