A prenatal case misunderstood as specimen confusion: 46,XY/46,XY chimerism.

Chimerism results from the fusion of two zygotes in a single embryo, whereas mosaicism results from mitotic errors in a single zygote. True human chimerism is rare, with fewer than 100 cases reported in the literature. Here, we report a case in which the fetus was identified as having tetragametic chimerism based on short tandem repeat - polymerase chain reaction analysis of the family observed during amniocentesis for advanced maternal age. The chimerism occurred via the fertilization of two ova by two spermatozoa, followed by the fusion of early embryos. The genotypes of the two amniotic fluid samples obtained successively by one puncture were completely different, and the sex chromosomes were XY. Karyotyping and copy number variation sequencing showed no abnormalities. The fetus was delivered at term and the phenotype of the newborn was normal.

Defining the scope of extended NIPS in Western China: evidence from a large cohort of fetuses with normal ultrasound scans.

BACKGROUND: Standard noninvasive prenatal screening(NIPS) is an accurate and reliable method to screen for common chromosome aneuploidies, such as trisomy 21, 18 and 13. Extended NIPS has been used in clinic for not only aneuploidies but also copy number variants(CNVs). Here we aim to define the range of chromosomal abnormalities that should be able to identify by NIPS in order to be an efficient extended screening test for chromosomal abnormalities. METHODS: A prospective study was conducted, involving pregnant women without fetal sonographic structural abnormalities who underwent amniocentesis. Prenatal samples were analyzed using copy number variation sequencing(CNV-seq) to identify fetal chromosomal abnormalities. RESULTS: Of 28,469 pregnancies included 1,022 (3.59%) were identified with clinically significant fetal chromosome abnormalities, including 587 aneuploidies (2.06%) and 435 (1.53%) pathogenic (P) / likely pathogenic (LP) CNVs. P/LP CNVs were found in all chromosomes, but the distribution was not uniform. Among them, P/LP CNVs in chromosomes 16, 22, and X exhibited the highest frequencies. In addition, P/LP CNVs were most common on distal ends of the chromosomes and in low copy repeat regions. Recurrent microdeletion/microduplication syndromes (MMS) accounted for 40.69% of total P/LP CNVs. The size of most P/LP CNVs (77.47%) was < 3 Mb. CONCLUSIONS: In addition to aneuploidies, the scope of extended NIPS should include the currently known P/LP CNVs, especially the regions with recurrent MMS loci, distal ends of the chromosomes, and low copy repeat regions. To be effective detection should include CNVs of < 3 Mb. Meanwhile, sufficient preclinical validation is still needed to ensure the clinical effect of extended NIPS.

Prenatal phenotype of Wolf-Hirschhorn syndrome: A case series and literature review.

OBJECTIVE: Wolf-Hirschhorn syndrome (WHS) is a congenital malformation syndrome with poor prognosis. It is associated with a heterozygous deletion of chromosome 4p16.3. Adequate knowledge of prenatal phenotypes and proper prenatal counseling are essential for intrauterine diagnosis. METHOD: We retrospectively analyzed 11 prenatal cases of WHS diagnosed using low-depth whole-genome sequencing (copy number variation sequencing) performed at our hospital from May 2017 to September 2022 and reviewed their prenatal ultrasound reports in detail. We also analyzed WHS cases (including prenatal and postnatal) with abnormal prenatal ultrasound findings in the published literature over the past 20 years. RESULTS: Among the 11 fetuses with a prenatal diagnosis of WHS in our hospital, four cases showed abnormal prenatal ultrasound findings, including shrunken kidneys, ventricular septal defect, a small stomach, fetal growth restriction (FGR), enlarged posterior fossa, and soft ultrasonic markers. Our four cases were combined with 114 published WHS cases with prenatal ultrasound abnormalities from other medical institutions. Of the 118 cases, 59.3% (70 of 118) were multiple malformations. The most frequent ultrasound features observed in all 118 cases were FGR (76.3%, 90 of 118), followed by facial anomalies (28.8%, 34 of 118), central nervous system anomalies (27.1%, 32 of 118), and soft ultrasound markers (23.7%, 28 of 118). Other less common phenotypes included cardiac anomalies (19.5%, 23 of 118), genitourinary anomalies (19.5%, 23 of 118), increased NT/NF (12.7%, 15 of 118), skeletal anomalies (11.9%, 14 of 118), a single umbilical artery (10.2%, 12 of 118), gastrointestinal anomalies (9.3%, 11 of 118), oligohydramnios (8.5%, 10 of 118), cystic hygroma (5.1%, six of 118), hydrops/pleural effusion/ascites (2.5%, three of 118), and polyhydramnios (2.5%, three of 118). CONCLUSION: This study improved our understanding of the prenatal presentation of WHS by analyzing prenatal ultrasound abnormalities. The timely identification of prenatal ultrasound abnormalities can provide accurate consultation for pregnant women, improve the prenatal detection of WHS, and enable early prenatal management and intervention of WHS.

Does isolated nuchal translucency from 2.5 to 2.9 mm increase the risk of fetal chromosome disease?

Increased fetal nuchal translucency (NT) is a common ultrasonic manifestation during pregnancy. Many studies have confirmed that NT ≥ 3 mm is a high risk factor for adverse pregnancy outcome. However, when NT is between 2.5 and 2.9 mm, will it increase the risk of fetal chromosome abnormalities and other diseases? What is the most appropriate method for prenatal chromosome evaluation? At present, it has not been widely reported in the literature, and the conclusion is also controversial. This prospective cohort study included fetal samples from women who underwent amniocentesis from 2017 to 2020. The samples of the experimental group were fetuses with NT ≥ 2.5 mm at 11 to 13 + 6 weeks of gestation, with or without ultrasonographic anomaly. The control group contained fetal NT < 2.5 mm without ultrasonographic anomalies. All amniotic fluid samples were tested by copy number variants sequencing. In 262 fetal samples with isolated NT from 2.5 to 2.9 mm, the detection rate of aneuploidy was 3.4% (9/262), and the risk of aneuploidy was significantly higher than that of the control group (1.4%, 32/2331) (relative risk 2.5, 95% CI 1.2-5.2). The detection rates of other pathogenic/likely pathogenic copy number variants in the two groups were 0.8% (2/262) and 1.3% (31/2331), respectively, which was not statistically significant (relative risk 0.6, 95% CI 0.1-2.4). Our results showed that isolated NT from 2.5 to 2.9 mm increased the risk of fetal chromosome aneuploidy. Therefore, noninvasive prenatal screening is recommended as the first choice for prenatal chromosome evaluation in this population.

[Application of copy number variation squencing for prenatal diagnosis].

OBJECTIVE: To assess the value of next-generation sequencing-based copy number variation sequencing (CNV-seq) for the detection of copy number variations (CNVs) in prenatal diagnosis. METHODS: The results of single nucleotide polymorphism array (SNP-array) for prenatal diagnosis from May 2018 to December 2020 were reviewed. Selected cases of CNVs of clinical significance or low-percentage mosaic aneuploidies were included. Preserved DNA samples of amniotic fluid DNA were detected by CNV-seq. The results of CNV-seq and CMA were analyzed. RESULTS: A total of 16 488 data of SNP-array were re-analyzed, and 343 DNA samples were selected for the CNV-seq assay. All samples were successfully analyzed. Compared with the SNP-array, the proportion of full concordance, partial concordance and missed detection was 91.5% (314/343), 1.2% (4/343) and 7.3% (25/343), respectively. The non-detection zones of CNV-seq were confirmed, which have encompassed the SHOX gene and AZFc region. CONCLUSION: With a high accuracy and wide genome-wide coverage, CNV-seq is worthy for a wide application in prenatal diagnosis, though the limitation of testing should be taken into consideration, and the appropriate prenatal diagnosis method should be selected for different populations to reduce the occurrence of birth defects.

Analysis of autosomal dominant genes impacted by copy number loss in 24,844 fetuses without structural abnormalities.

BACKGROUND: The broad application of high-resolution chromosome detection technology in prenatal diagnosis has identified copy number loss (CNL) involving autosomal dominant (AD) genes in certain fetuses. Exon sequencing of fetuses exhibiting structural anomalies yields diagnostic information in up to 20% of cases. However, there is currently no relevant literature about the genetic origin and pregnancy outcome of CNL involving AD genes in fetuses without structural abnormalities. RESULTS: This was a prospective study involving pregnant women who underwent amniocentesis for fetal copy number variation sequencing (CNVseq). Detection of parent-of-origin was suggested in cases of samples with CNL involving AD genes and the pregnancy outcome was monitored. Amniotic fluid samples from 24,844 fetuses without structural abnormalities were successfully tested via CNVseq. The results showed that 134 fetuses (0.5%) had small CNL (< 10 Mb) containing AD genes, after excluding microdeletion and microduplication syndrome and polymorphisms. By monitoring the pregnancy outcomes of the 134 fetuses, we found that 104 (77.6%) were good, 13 (9.7%) were adverse, and 17 (12.7%) pregnant women voluntarily chose to terminate pregnancy. Of the 13 fetuses with adverse pregnancy outcomes, only 2 fetuses had phenotypes consistent with those of diseases caused by AD genes involved in CNL. CONCLUSIONS: The overall prognosis for fetuses without family history or structural abnormalities but with small CNL containing AD genes detected during pregnancy is good. The genetic origin, overlap status of established haploinsufficient gene and/or region, size of the CNL, and genetic mode may affect the pathogenicity of the CNL.

Copy number variation sequencing combined with quantitative fluorescence polymerase chain reaction in clinical application of pregnancy loss.

PURPOSE: In this study, we evaluated the feasibility of the combining CNV-seq and quantitative fluorescence polymerase chain reaction (QF-PCR) for miscarriage analysis in clinical practice. METHODS: Over a 35-month period, a total of 389 fetal specimens including 356 chorionic villi and 33 fetal muscle tissues were analyzed by CNV-seq and QF-PCR. Relationships between the risk factors (e.g., advanced maternal age, abnormal pregnancy history, and gestational age) and incidence of these chromosomal abnormalities were further analyzed by subgroup. RESULTS: Clinically significant chromosomal abnormalities were identified in 58.95% cases. Aneuploidy was the most common abnormality (46.84%), followed by polyploidy (8.16%) and structural chromosome anomalies (3.95%). In sub-group analysis, significant differences were found in the total frequency of chromosomal abnormalities between the early abortion and the late abortion group, as well as in the distribution of chromosomal abnormalities between the advanced and the younger maternal age group. Meanwhile, the results of the logistic regression analysis identified a trend suggesting that the percentage of fetal chromosomal abnormalities is significantly higher in advanced maternal age, lesser gestational age, and lesser number of prior miscarriages. CONCLUSION: Our study suggests that CNV-seq and QF-PCR are efficient and reliable technologies in the fetal chromosome analysis of miscarriages and could be used as a routine selection method for the genetic analysis of spontaneous abortion.

Segmental aneuploidies in fetuses with isolated echogenic intracardiac focus among women younger than 35 years.

Studies on the occurrence of segmental aneuploidoidy in fetuses with isolated echogenic intracardiac focus (EIF) are scarce. The aim of this study was to analyze whether there is an association between abnormal segmental aneuploidies and isolated EIF. This was a prospective case-control study. The study participants in the case group were fetuses that were diagnosed with isolated EIF. Samples without fetal ultrasound abnormalities but received prenatal diagnosis for other reasons (serological screening high-risk, voluntary request) were set as controls. All pregnant women were younger than 35 years old at the expected date of childbirth. Copy number variation sequencing (CNV-seq) was performed for all samples. The case group and control group successfully underwent CNV-seq analysis and exhibited 1,099 and 5,616 amniotic fluid samples, respectively. The detection rates of abnormal segmental aneuploidies in the case group and control group were 0.6% (7/1,099) and 1.1% (64/5,616), respectively; no statistically significant difference was found between the two groups (x2 = 2.220, P = 0.136). Isolated EIF did not increase the risk of fetal segmental aneuploidies.

Influence of the detection of parent-of-origin on the pregnancy outcomes of fetuses with copy number variation of unknown significance.

The widespread application of high-resolution chromosome detection technology in clinical practice has identified many variants of unknown significance (VOUS) in prenatal diagnosis. The purpose of this study was to prospectively analyze the chromosomal results of parents and the follow-up information of pregnancy outcomes of prenatal samples with VOUS, so as to determine the influence of the detection of parent-of-origin on the pregnancy outcomes of fetuses with VOUS. The present study analyzed amniotic fluid samples obtained from women with different risk indications between February 2017 and December 2018. The samples were subjected to copy number variation sequencing, and detection of parent-of-origin was suggested in cases of samples with VOUS. The pregnancy outcome was followed up. In a total of 14073 amniotic fluid samples, 729 cases of VOUS were detected (5.2%, 729/14073) and 721 cases were followed up successfully. Among the 721 cases, 525 patients agreed to detect the parent-of-origin (72.8%, 525/721). It was revealed that the VOUS in 460 of the fetuses were hereditary (87.6%, 460/525). The percentages of abnormal pregnancy outcomes (included pregnancy loss, fetal pathological abnormality, preterm delivery, neonatal death, birth defects) in the inherited, de novo, and refusal to detect the parent-of-origin (i.e. unknown origin) groups were 4.3% (20/460), 6.2% (4/65), and 6.6% (13/196), respectively. There was no significant difference among the three groups (P > 0.05). The rate of voluntary termination of pregnancy (TOP) in the unknown origin group was significantly higher than that in the group that had determined the parent-of-origin (14.3% vs 7.4%, P = 0.005). There is currently no evidence that suggests that the proportion of abnormal pregnancy outcomes is higher in fetuses with VOUS than in other fetuses. However, the present study revealed that determining the parent-of-origin affects the decision to undergo voluntary TOP, as the rate of voluntary TOP in the group that refused detection was higher than that in the group that consented.

Identification of copy number variations among fetuses with ultrasound soft markers using next-generation sequencing.

A prospective analysis investigating the associations between pathogenic copy number variations (pCNVs) and ultrasound soft markers (USMs) in fetuses and evaluating the clinical value of copy number variation sequencing (CNV-seq) in such pregnancy studies was carried out. 3,398 unrelated Chinese women with singleton pregnancies and undergone amniocentesis at 18-36 weeks of gestation for fetal CNV-seq were included. According to the prenatal fetal ultrasound screening results, the samples were divided into 3 groups: normal ultrasound (n = 2616), solitary USM (n = 663), and two or more USMs (n = 119). CNV-seq was performed successfully using all samples. The prevalence of pCNVs in fetuses with normal ultrasound and USMs was 3.03% (79/2616) and 2.94% (23/782), respectively. The risk of segmental aneuploidies was significantly higher in the two or more USMs group (5/119, 4.20%) than in the normal ultrasound (27/2616, 1.04%) or solitary USM (9/663, 1.36%) groups (p = 0.002 and p = 0.031, respectively). Assuming that the resolution of karyotyping is ~5 Mb, a cytogenetic analysis would miss 33 of 102 (32.35%) pCNVs in these samples. Our results suggest an association between pCNVs and fetal USMs; multiple USMs indicate an increased risk of fetal segmental aneuploidies. In prenatal diagnostic testing, CNV-Seq identified additional, clinically significant cytogenetic information.

[Clinical Significance of Urinary Microalbumin to Creatinine Ratio in Physical Examinations].

OBJECTIVE: To-determine the association between urinary microalbumin to creatinine ratio (mALB/Cr) and metabolic indicators in people undergoing physical examinations. METHODS: A total of 4 184 people who took physical examinations in West China Hospital, Sichuan University from November 2013 to October 2014 participated in this study. We measured their body mass index (BMI), systolic blood pressure (SBP), diastolic blood pressure (DBP), waistline, hipline, Waist-to-hip ratio (WHR), urinary mALB/Cr, serum glucose (GLU), total cholesterol (TC), triglyceride (TG) , high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C), blood urea nitrogen (BUN), serum creatinine (SCr) , uric acid (UA), cystatin C (Cys-C), glomerular filtration rate (eGFR) and homocysteine (Hcy). RESULTS: (1) The participants had a median (interquartile range) mALB/Cr of 5.7 (3.1-11.8) mg/g: 5.4 (3.0-11.3) mg/g for males and 6.3 (3.6-13.2) mg/g for females (P < 0.05). (2) About 10.95% participants (10.96% for males and 10.90% for females) had a mALB/Cr ≥ 30 mg/g. (3) mALB/Cr increased with age. (4) BMI, SBP, DBP, waistline, WHR, GLU, HDL-C, TG, SCr, BUN, UA, eGFR and Cys-C were associated the distribution of participants (P < 0.05) across the three groups of mALB/Cr: normal (< 30 mg/g), microalbuminuria (30-300 mg/g) , and proteinuria (> 300 mg/g). (5) Logistic regression demonstrated that age, SBP, WHR, GLU, TG and eGFR were significant predictors of albuminuria. CONCLUSION: A high level of abnormal/positive mALB/Cr was found in people undergoing physical examinations. Increased age, SBP, WHR, GLU, TG and decreased eGFR are major risk factors of abnormal mALB/Cr. mALB/Cr should be monitored, especially in the elderly and those with high-metabolic-syndrome.