Clinical Utility of the Prenatal BACs-on-Beads™ Assay in Invasive Prenatal Diagnosis

Background: The prenatal BACs-on-Beads™ (PNBoBs™) assay has been applied worldwide for prenatal diagnosis. However, there are neither guidelines nor consensus on choosing patients, sample types, or clinical pathways for using this technique. Moreover, different perspectives have emerged regarding its clinical value. This study aimed to evaluate its clinical utility in the context of clinical practice located in a prenatal diagnostic center in Xiamen, a city in southeast China.Methods: We tested 2,368 prenatal samples with multiple referral indications using both conventional karyotyping and PNBoBs™. Positive results from PNBoBs™ were verified using current gold-standard approaches.Results: The overall rates for the detection of pathogenic copy number variation (pCNV) by karyotyping and PNBoBs™ were 1.9% (46/2,368) and 2.0% (48/2,368), respectively. The overall detection rate of karyotyping combined with PNBoBs™ for pCNV was 2.3% (54/2,368). A total of 13 cases of copy number variation (CNV)with a normal karyotype were detected by PNBoBs™. Another case with a normal karyotype that was detected as a CNV of sex chromosomes by PNBoBs™ was validated to be maternal cell contamination by short tandem repeat analysis.Conclusion: Karyotyping combined with PNBoBs™ can improve both the yield and efficiency of prenatal diagnosis and is appropriate in the second trimester in all patients without fetal ultrasound anomalies who undergo invasive prenatal diagnosis.

The femur too short? 1373 fetuses with short femur during second-trimester screening

Purpose A short fetal femur in prenatal diagnosis might be an indicator for intrauterine growth retardation (IUGR), a genetically determined small child (SGA) with or without associated fetal malformations and/or an adverse fetal outcome. Methods 1373 singleton pregnancies with a femoral length < 5th percentile detected between 1999 and 2015 during second-trimester screening in a tertiary prenatal diagnostic center were subjected to a descriptive retrospective analysis with regard to fetal characteristics as well as pregnancy outcome. Results 685 (49.9%) fetuses presented an isolated short femur, while 688 (50.1%) showed additional abnormalities. 293 (42.6%) of those were SGA babies without any malformation, while 395 (57.4%) had one or more severe anomaly of the following organ systems: 157 (11.5%) cardiovascular, 101 (7.4%) musculoskeletal, 82 (6.0%) urogenital, 72 (5.2%) cerebrocephalic, 50 (3.6%) gastrointestinal, and 5 (0.4%) thoracic. 75 (5.5%) of the fetuses showed chromosomal aberrations of which Trisomy 13, 18 and 21 were found in 2, 13 and 27 of the cases, respectively. Fetuses with associated malformations had a significantly lower live birth rate than those without (64.2% vs. 98.1%, p < 0.001); in addition, a higher rate of preterm births 36.6% vs. 11.3%, p < 0.001) and SGA babies (51.4% vs. 30.4%, p < 0.001) were observed in the first collective. Conclusion Diagnosis of a short fetal femur should lead to an extended organ screening; in the case of associated abnormalities, additional genetic testing has to be offered, as well as intensified pregnancy monitoring in pregnancies at risk for IUGR and/or preterm birth.

Significance of the ‘line sign’ in the diagnosis of congenital imperforate anus on prenatal ultrasound

Background The prenatal diagnosis of foetal imperforate anus is difficult. Most previous studies have been case reports. To provide useful information for diagnosing foetal imperforate anus, a retrospective review of diagnostic approaches was conducted. Ultrasonography was performed in 19 cases of foetal imperforate anus from 2016 to 2019 at our prenatal diagnostic centre. The prenatal sonographic features and outcomes of each case were collected and evaluated. Result The anal sphincter of a normal foetus shows the ‘target sign’ on cross-sectional observation. Of the 19 cases of imperforate anus, 16 cases were diagnosed by the ultrasound image feature called the ‘line sign’. 1 case with tail degeneration was low type imperforate anus with the irregular ‘target sign’ not a real ‘target sign’. There was two false-negative case, in which the ‘target sign’ was found, but irregular. Conclusion In this study, we find that the anus of a foetus with imperforate anus presents a ‘line sign’ on sonographic observation. The absence of the ‘target sign’ and then the presence of the ‘line sign’ can assist in the diagnosis of imperforate anus. The ‘line sign’ can be used as a secondary assessment to determine the type of the malformation following non visualization of the ‘target sign’. The higher the position of the imperforate anus is, the more obvious the ‘line sign’. It is worth noting that the finding of the short ‘line sign’ and irregularr ‘target sign’ can not ignore the low type imperforate anus.

How COVID-19 pandemic is changing the practice of prenatal screening and diagnosis?

Objectives To evaluate the impact of the COVID-19 pandemic on prenatal screening and diagnostic tests. Methods We conducted a retrospective study with pregnant women attending to the perinatology department of a tertiary referral center. The pre-COVID-19 period between 11 March 2019 and 10 March 2020 and COVID-19 period between 11 March 2020 and 10 March 2021 were evaluated. Both periods were compared in terms of outpatient visits, ultrasound examinations, prenatal screening and diagnostic tests. The correlation of deaths related to COVID-19 pandemic on these parameters was also assessed. Results A total of 38,918 patients were examined and 28,452 ultrasound examinations, 26,672 prenatal screening tests and 1,471 prenatal diagnostic tests were performed over two years. During COVID-19 pandemic, number of outpatient visits decreased by 25.2%, ultrasound examinations decreased by 44.2%, prenatal screening tests decreased by 36.2% and prenatal diagnostic tests decreased by 30.7%. Statistically significant correlation was not observed between deaths related to COVID-19 and outpatient visits (p=0.210), ultrasound examinations (p=0.265), prenatal screening (p=0.781) and diagnostic tests (p=0.158). Among indications of prenatal diagnostic tests, maternal anxiety was significantly higher in COVID-19 period (p=0.023). There was significant decrease in the detection of fetuses with trisomy 21 (p=0.047) and a significant increase in the detection of fetuses with Turner syndrome (p=0.017) during COVID-19 period. Conclusions The COVID-19 pandemic has severely impacted antenatal care. Prenatal fetal screening and diagnosis was adversely affected by the pandemic in terms of detecting genetic and structural anomalies.

Mandibular Measurements at the 20-Week Anatomy Ultrasound as a Prenatal Diagnostic Predictor of Pierre Robin Sequence

Background Pierre Robin Sequence (PRS) is characterized by micrognathia, glossoptosis, and upper airway obstruction. Early recognition and appropriate perinatal management is crucial for optimizing outcomes. This study aimed to evaluate 20-week fetal ultrasounds to determine if specific mandibular measurements could predict PRS diagnosis and disease severity. Methods A retrospective case-control study of 48 patients with PRS and gender-matched controls was performed. Medical records were reviewed for respiratory and surgical interventions. Three parameters to assess micrognathia were measured on mid-sagittal profile ultrasound images: frontal nasal-mental angle (FNMA), facial-maxillary angle (FMA), and alveolar overjet. Student's t-test and univariate logistic regression was performed. P ≤ 0.05 was considered statistically significant. Results Patients with PRS demonstrated a significantly smaller mean FNMA compared to the control group, 129.3 ± 8.6° and 137.4 ± 3.2°, respectively (p < 0.0001), as well as significantly smaller mean FMA, 63.2 ± 9.2° and 74.8 ± 6.1°, respectively (p < 0.0001). The PRS group also demonstrated significantly larger mean alveolar overjet compared to the control group, 3.9 ± 1.4 mm and 2.1 ± 0.9 mm, respectively (p < 0.0001). The odds of respiratory intervention increased among cases when FMA was <68°. Additionally, there was a significant difference in median overjet between patients with PRS who did and did not require respiratory intervention. Conclusions Mandibular features on the 20-week ultrasound can be measured to predict diagnosis and severity of PRS. This is an important first step to prepare for potential respiratory intervention at delivery to minimize perinatal hypoxia. Alveolar overjet, previously not described in prenatal ultrasound literature, is measurable and has utility in prenatal screening for PRS, as do FMA and FNMA.

Isolation and Enrichment of Circulating Fetal Cells for NIPD: An Overview

Prenatal diagnosis plays a crucial role in clinical genetics. Non-invasive prenatal diagnosis using fetal cells circulating in maternal peripheral blood has become the goal of prenatal diagnosis, to obtain complete fetal genetic information and avoid risks to mother and fetus. The development of high-efficiency separation technologies is necessary to obtain the scarce fetal cells from the maternal circulation. Over the years, multiple approaches have been applied, including choice of the ideal cell targets, different cell recovering technologies, and refined cell isolation yield procedures. In order to provide a useful tool and to give insights about limitations and advantages of the technologies available today, we review the genetic research on the creation and validation of non-invasive prenatal diagnostic testing protocols based on the rare and labile circulating fetal cells during pregnancy.

The impact of preimplantation genetic testing for aneuploidy on prenatal screening

Objectives To determine whether preimplantation genetic testing for aneuploidy (PGT-A) is associated with a reduced risk of abnormal conventional prenatal screening results in singleton pregnancies conceived using in vitro fertilization (IVF). Methods This was a retrospective cohort study of singleton IVF pregnancies conceived from a single tertiary care center between January 2014 and September 2019. Exclusion criteria included mosaic embryo transfers, vanishing twin pregnancies, and cycles with missing outcome data. Two cases of prenatally diagnosed aneuploidy that resulted in early voluntary terminations were also excluded. The primary outcome of abnormal first or second-trimester combined screening results was compared between two groups: pregnancy conceived after transfer of a euploid embryo by PGT-A vs. transfer of an untested embryo. Multivariable backwards-stepwise logistic regression with Firth method was used to adjust for potential confounders. Results Of the 419 pregnancies included, 208 (49.6%) were conceived after transfer of a euploid embryo by PGT-A, and 211 (50.4%) were conceived after transfer of an untested embryo. PGT-A was not associated with a lower likelihood of abnormal first-trimester (adjusted OR 1.64, 95% CI 0.82–3.39) or second-trimester screening results (adjusted OR 0.96, 95% CI 0.56–1.64). The incidences of cell-free DNA testing, fetal sonographic abnormalities, genetic counseling, and invasive prenatal diagnostic testing were similar between the two groups. Conclusions Our data suggest that PGT-A is not associated with a change in the likelihood of abnormal prenatal screening results or utilization of invasive prenatal diagnostic testing. Counseling this patient population regarding the importance of prenatal screening and prenatal diagnostic testing, where appropriate, remains essential.

More than sample providers: how genetic researchers in Pakistan mobilized a prenatal diagnostic service for thalassemia

While unequally resourced partners from the so-called global South are often considered ‘mere sample providers’ in larger international genomics collaborations, in this paper, we show how they strategically work to mobilize their role in a global system of tissue exchange to deliver services for local communities. We unpack how a prenatal diagnostic service for thalassemia in Pakistan emerged out of the maneuvering efforts of internationally connected Pakistani researchers. By tracing the distributed capacities that emerged and circulated as they set about improving medical genetics in Pakistan, we outline some key conditions that led to the establishment of the service: first, the scale of unmet needs that geneticists faced when collecting data as part of their research that made medical genomics a relevant field; secondly, joint efforts between researchers and physicians that were engaged with the challenge of decreasing disease prevalence through diagnostics and abortion; and finally, the ways in which international research collaborations helped generate resources to improve medical genetics in Pakistan. To understand how genetic research and medicine is currently being developed in Pakistan, we need to ethnographically re-center our analyses in ways that allow us to identify the resourceful ways in which researchers maneuvre to secure locally relevant outcomes.

Determinant of Prenatal Diagnostic Testing Among Women with Increased Risk of Fetal Aneuploidy and Genetic Disorders.

Objective: This study aimed to assess factors that influence patients’ decisions in accepting prenatal diagnostic testing following genetic counseling for increased risk of fetal aneuploidy. Methods: A retrospective cohort study of women at increased risk of fetal aneuploidy who had genetic counseling from January 2012 to December 2016 at a single academic center. Demographics, indications for genetic counseling and rates of diagnostic testing were collected and compared between those who accepted diagnostic testing and those who chose cell free DNA. The variables were analyzed using chi-square, Fisher exact test, and multiple logistic regression. Result: Of the 2373 pregnant women who underwent genetic counseling for increased risk of fetal aneuploidy during the study period, 321 women had diagnostic testing (13.5%). Women at 35 years and older accepted diagnostic testing more than women younger than 35 years (20.7% versus 11.5%, p < 0.001). Asian women accepted diagnostic testing at 27.7% more than white, non-Hispanic Black and Hispanic women at 18.0%, 12.1% and 11.7% respectively, p = 0.002. Number of indications for genetic counseling influenced the likelihood of accepting diagnostic testing. Women with one indication had 11.5% acceptance of diagnostic testing; and with two and three indications, it was 17.0% and 29.2% respectively. The commonest indication for diagnostic testing was cystic hygroma (RR 7.5, 95% CI 3.12-8.76 p < 0.001). The relative risk of diagnostic testing for fetuses with shortened long bones; femur and humerus, thickened nuchal fold, echogenic bowel, single umbilical artery, increased nuchal translucency were 4.0, 3.3, 3.1, 2.7, and 2.7 respectively. Abnormal serum analyte alone was associated with less acceptance of diagnostic testing (RR 0.8, 95% CI 0.7 – 0.96, p = 0.017). Conclusion: Age, race, ethnicity and cumulative number of indications for genetic counseling influenced acceptance of diagnostic testing in at-risk women of fetal aneuploidy and genetic disorders