Aspiring toward equitable benefits from genomic advances to individuals of ancestrally diverse backgrounds

Advancements in genomic technologies have shown remarkable promise for improving health trajectories. The Human Genome Project has catalyzed the integration of genomic tools into clinical practice, such as disease risk assessment, prenatal testing and reproductive genomics, cancer diagnostics and prognostication, and therapeutic decision making. Despite the promise of genomic technologies, their full potential remains untapped without including individuals of diverse ancestries and integrating social determinants of health (SDOHs). The NHGRI launched the 2020 Strategic Vision with ten bold predictions by 2030, including "individuals from ancestrally diverse backgrounds will benefit equitably from advances in human genomics." Meeting this goal requires a holistic approach that brings together genomic advancements with careful consideration to healthcare access as well as SDOHs to ensure that translation of genetics research is inclusive, affordable, and accessible and ultimately narrows rather than widens health disparities. With this prediction in mind, this review delves into the two paramount applications of genetic testing-reproductive genomics and precision oncology. When discussing these applications of genomic advancements, we evaluate current accessibility limitations, highlight challenges in achieving representativeness, and propose paths forward to realize the ultimate goal of their equitable applications.

Placental, maternal, fetal, and technical origins of false-positive cell-free DNA screening results

The introduction of noninvasive prenatal testing has resulted in substantial reductions to previously accepted false-positive rates of prenatal screening. Despite this, the possibility of false-positive results remains a challenging consideration in clinical practice, particularly considering the increasing uptake of genome-wide noninvasive prenatal testing, and the subsequent increased proportion of high-risk results attributable to various biological events besides fetal aneuploidy. Confined placental mosaicism, whereby chromosome anomalies exclusively affect the placenta, is perhaps the most widely accepted cause of false-positive noninvasive prenatal testing. There remains, however, a substantial degree of ambiguity in the literature pertaining to the clinical ramifications of confined placental mosaicism and its potential association with placental insufficiency, and consequentially adverse pregnancy outcomes including fetal growth restriction. Other causes of false-positive noninvasive prenatal testing include vanishing twin syndrome, in which the cell-free DNA from a demised aneuploidy-affected twin triggers a high-risk result, technical failures, and maternal origins of abnormal cell-free DNA such as uterine fibroids or unrecognized mosaicisms. Most concerningly, maternal malignancies are also a documented cause of false-positive screening results. In this review, we compile what is currently known about the various causes of false-positive noninvasive prenatal testing.

Fetal fraction of cell-free DNA in noninvasive prenatal testing and adverse pregnancy outcomes: a nationwide retrospective cohort study of 56,110 pregnant women

BACKGROUND

Noninvasive prenatal testing by cell-free DNA analysis is offered to pregnant women worldwide to screen for fetal aneuploidies. In noninvasive prenatal testing, the fetal fraction of cell-free DNA in the maternal circulation is measured as a quality control parameter. Given that fetal cell-free DNA originates from the placenta, the fetal fraction might also reflect placental health and maternal pregnancy adaptation.

OBJECTIVE

This study aimed to assess the association between the fetal fraction and adverse pregnancy outcomes.

STUDY DESIGN

We performed a retrospective cohort study of women with singleton pregnancies opting for noninvasive prenatal testing between June 2018 and June 2019 within the Dutch nationwide implementation study (Trial by Dutch Laboratories for Evaluation of Non-Invasive Prenatal Testing [TRIDENT]-2). Multivariable logistic regression analysis was used to assess associations between fetal fraction and adverse pregnancy outcomes. Fetal fraction was assessed as a continuous variable and as <10th percentile, corresponding to a fetal fraction <2.5%.

RESULTS

The cohort comprised 56,110 pregnancies. In the analysis of fetal fraction as a continuous variable, a decrease in fetal fraction was associated with increased risk of hypertensive disorders of pregnancy (adjusted odds ratio, 2.27 [95% confidence interval, 1.89-2.78]), small for gestational age neonates <10th percentile (adjusted odds ratio, 1.37 [1.28-1.45]) and <2.3rd percentile (adjusted odds ratio, 2.63 [1.96-3.57]), and spontaneous preterm birth from 24 to 37 weeks of gestation (adjusted odds ratio, 1.02 [1.01-1.03]). No association was found for fetal congenital anomalies (adjusted odds ratio, 1.02 [1.00-1.04]), stillbirth (adjusted odds ratio, 1.02 [0.96-1.08]), or neonatal death (adjusted odds ratio, 1.02 [0.96-1.08]). Similar associations were found for adverse pregnancy outcomes when fetal fraction was <10th percentile.

CONCLUSION

In early pregnancy, a low fetal fraction is associated with increased risk of adverse pregnancy outcomes. These findings can be used to expand the potential of noninvasive prenatal testing in the future, enabling the prediction of pregnancy complications and facilitating tailored pregnancy management through intensified monitoring or preventive measures.

Obstetrical, perinatal, and genetic outcomes associated with nonreportable prenatal cell-free DNA screening results

BACKGROUND

The clinical implications of nonreportable cell-free DNA screening results are uncertain, but such results may indicate poor placental implantation in some cases and be associated with adverse obstetrical and perinatal outcomes.

OBJECTIVE

This study aimed to assess the outcomes of pregnancies with nonreportable cell-free DNA screening in a cohort of patients with complete genetic and obstetrical outcomes.

STUDY DESIGN

This was a prespecified secondary analysis of a multicenter prospective observational study of prenatal cell-free DNA screening for fetal aneuploidy and 22q11.2 deletion syndrome. Participants who underwent cell-free DNA screening from April 2015 through January 2019 were offered participation. Obstetrical outcomes and neonatal genetic testing results were collected from 21 primary-care and referral centers in the United States, Europe, and Australia. The primary outcome was risk for adverse obstetrical and perinatal outcomes (aneuploidy, preterm birth at <28, <34, and <37 weeks' gestation, preeclampsia, small for gestational age or birthweight <10th percentile for gestational week, and a composite outcome that included preterm birth at <37 weeks, preeclampsia, small for gestational age, and stillbirth at >20 weeks) after nonreportable cell-free DNA screening because of low fetal fraction or other causes. Multivariable analyses were performed, adjusting for variables known to be associated with obstetrical and perinatal outcomes, nonreportable results, or fetal fraction.

RESULTS

In total, 25,199 pregnant individuals were screened, and 20,194 were enrolled. Genetic confirmation was missing in 1165 (5.8%), 1085 (5.4%) were lost to follow-up, and 93 (0.5%) withdrew; the final study cohort included 17,851 (88.4%) participants who had cell-free DNA, fetal or newborn genetic confirmatory testing, and obstetrical and perinatal outcomes collected. Results were nonreportable in 602 (3.4%) participants. A sample was redrawn and testing attempted again in 427; in 112 (26.2%) participants, results were again nonreportable. Nonreportable results were associated with higher body mass index, chronic hypertension, later gestational age, lower fetal fraction, and Black race. Trisomy 13, 18, or 21 was confirmed in 1.6% with nonreportable tests vs 0.7% with reported results (P=.013). Rates of preterm birth at <28, 34, and 37 weeks, preeclampsia, and the composite outcome were higher among participants with nonreportable results, and further increased among those with a second nonreportable test, whereas the rate of small for gestational age infants was not increased. After adjustment for confounders, the adjusted odds ratios were 2.2 (95% confidence interval, 1.1-4.4) and 2.6 (95% confidence interval, 0.6-10.8) for aneuploidy, and 1.5 (95% confidence interval, 1.2-1.8) and 2.1 (95% confidence interval, 1.4-3.2) for the composite outcome after a first and second nonreportable test, respectively. Of the patients with nonreportable tests, 94.9% had a live birth, as opposed to 98.8% of those with reported test results (adjusted odds ratio for livebirth, 0.20 [95% confidence interval, 0.13-0.30]).

CONCLUSION

Patients with nonreportable cell-free DNA results are at increased risk for a number of adverse outcomes, including aneuploidy, preeclampsia, and preterm birth. They should be offered diagnostic genetic testing, and clinicians should be aware of the increased risk of pregnancy complications.

First-trimester septated cystic hygroma, marked non-immune fetal hydrops, 45,X and coarctation of the aorta with neonatal survival

Marked first-trimester nonimmue hydrops fetalis and 45,X with neonatal survival.

Experiences of receiving an increased chance of sex chromosome aneuploidy result from non-invasive prenatal testing in Australia: "A more complicated scenario than what I had ever realized"

Many non-invasive prenatal testing (NIPT) platforms screen for sex chromosome aneuploidy (SCA) and SCA analysis is generally included in Australia where NIPT is available as a self-funded test. Little is known about the experience of receiving an NIPT result indicating an increased chance of SCA. This study aimed to explore the experiences of people who received this result and their perspectives on the information, care, and support they received from healthcare practitioners (HCPs). Semi-structured interviews were conducted with people who received an NIPT result indicating an increased chance of SCA and continued their pregnancy. Most participants only had contact with a genetic counselor after receiving their result. Transcribed data were analyzed using rigorous thematic analysis to identify important patterns and themes. Participants (18 women, 2 male partners) described embarking on NIPT, primarily based on advice from their HCP and without much consideration. Consequently, participants expressed feeling unprepared for the unanticipated complexity of their NIPT result and were faced with making a time-sensitive decision about a condition they had not previously considered. While more pre-test information was desired, timely access to genetic counseling post-test assisted with adjustment to the result. These findings suggest that routinization of NIPT may be compromising informed decision-making, resulting in unpreparedness for an increased chance result. Given the increasing uptake and expanding scope of NIPT, resources should be dedicated to educating HCPs offering NIPT and ensuring timely access to genetic counseling post-result. With appropriate funding, genetics services may be able to play a central role in offering information and support to both people who undertake NIPT and their HCPs ordering the testing. Implementing a publicly funded screening program in Australia could assist with standardizing prenatal screening care pathways and consequently better access to appropriate resources.

The accuracy of cell-free DNA screening for fetal segmental copy number variants: A systematic review and meta-analysis

BACKGROUND

The performance of cell-free DNA (cfDNA) screening for microscopic copy number variants (CNVs) is unclear.

OBJECTIVES

This was a systematic review and meta-analysis to investigate the sensitivity, specificity and positive predictive value (PPV) of cfDNA screening for CNVs.

SEARCH STRATEGY

Articles published in EMBASE, PubMed or Web of Science before November 2022 were screened for inclusion. This protocol was registered with PROSPERO (23 March 2021, CRD42021250849) prior to initiation.

SELECTION CRITERIA

Articles published in English, detailing diagnostic outcomes for at least 10 high-risk CNV results with cfDNA were considered for inclusion.

DATA COLLECTION AND ANALYSIS

The PPV was calculated and pooled with random-effects models for double-arcsine transformed proportions, using cases with diagnostic confirmation. Overall sensitivity, specificity and a summary receiver-operating characteristics (ROC) curve were calculated using bivariate models. The risk of bias was assessed using QUADAS-2.

MAIN RESULTS

In all, 63 articles were included in the final analysis, detailing 1 591 459 cfDNA results. The pooled PPV was 37.5% (95% confidence interval [CI] 30.6-44.8), with substantial statistical heterogeneity (I²  = 93.9%). Bivariate meta-analysis estimated sensitivity and specificity to be 77.4% (95% CI 65.7-86.0) and 99.4% (95% CI 98.0-99.8), respectively, with an area under the summary ROC curve of 0.947 (95% CI 0.776-0.984).

CONCLUSIONS

Approximately one-third of women who screen high-risk for CNVs with cfDNA will have an affected fetus. This value is of importance for screening counselling.

Cytogenetic outcomes following a failed cell-free DNA screen: a population-based retrospective cohort study of 35,146 singleton pregnancies

BACKGROUND

Cell-free fetal DNA screening is routinely offered to pregnant individuals to screen for aneuploidies. Although cell-free DNA screening is consistently more accurate than multiple-marker screening, it sometimes fails to yield a result. These test failures and their clinical implications are poorly described in the literature. Some studies suggest that a failed cell-free DNA screening result is associated with increased likelihood of cytogenetic abnormalities.

OBJECTIVE

This study aimed to assess the association between a failed cell-free DNA test and common aneuploidies. The objectives were to determine: (1) the proportion of test failures on first and subsequent attempts, and (2) whether a failed cell-free DNA screen on first attempt is associated with increased likelihood of common aneuploidies (trisomies 21, 18, and 13, and sex chromosome aneuploidies).

STUDY DESIGN

This was a population-based retrospective cohort study using data from Ontario's prescribed maternal and child registry, Better Outcomes Registry and Network Ontario. The study included all singleton pregnancies in Ontario with an estimated date of delivery from September 1, 2016 to March 31, 2019 that had a cell-free DNA screening record in the registry. Specific outcomes (trisomies 21, 18, and 13, and sex chromosome aneuploidies) of pregnancies with a failed cell-free DNA screen on first attempt were compared with those of pregnancies with low-risk cell-free DNA-screening results using modified Poisson regression adjusted for funding status (publicly funded vs self-paid), gestational age at screening, method of conception, and maternal age for autosomal aneuploidies.

RESULTS

Our cohort included 35,146 pregnancies that had cell-free DNA screening during the study period. The overall cell-free DNA screening failure rate was 4.8% on first attempt and 2.2% after multiple attempts. An abnormal cytogenetic result for trisomies 21, 18, and 13, or sex chromosome aneuploidies was identified in 19.4% of pregnancies with a failed cell-free DNA screening for which cytogenetic testing was performed. Pregnancies with a failed cell-free DNA screen on first attempt had a relative risk of 130.3 (95% confidence interval, 64.7-262.6) for trisomy 21, trisomy 18, or trisomy 13, and a risk difference of 5.4% (95% confidence interval, 2.6-8.3), compared with pregnancies with a low-risk result. The risk of sex chromosome aneuploidies was not significantly greater in pregnancies with a failed result compared with pregnancies with a low-risk result (relative risk, 2.7; 95% confidence interval, 0.9-7.9; relative difference, 1.2%; 95% confidence interval, -0.9 to 3.2).

CONCLUSION

Cell-free DNA screening test failures are relatively common. Although repeated testing improves the likelihood of an informative result, pregnancies with a failed cell-free DNA screen upon first attempt remain at increased risk for common autosomal aneuploidies, but not sex chromosome aneuploidies.

First Trimester Screening - Current Status and Future Prospects After Introduction of Non-invasive Prenatal Testing (NIPT) at a Tertiary Referral Center

Objective To investigate the uptake of different components of first trimester screening (FTS) and the impact on invasive diagnostic testing (IPT) since the introduction of non-invasive prenatal testing (NIPT) at a level III center. Methods Retrospective data analysis was conducted for singleton pregnancies that presented for FTS between 01/2019-12/2019 (group 1, n = 990). Patients were categorized into three risk groups: low risk for trisomy 21 (< 1 : 1000), intermediate risk (1 : 101-1 : 1000) and high risk (≥ 1 : 100). Uptake of NIPT and IPT was analyzed for each of the risk groups. Results were compared to a previous cohort from 2012/2013 (immediately after the introduction of NIPT, group 2, n = 1178). Results Group 1 showed a significant increase in the use of NIPT as part of FTS (29.5% vs. 3.7% for group 2, p = 0.001) in all three risk groups. Overall IPT rates were lower in group 1 (8.6%) vs. group 2 (11.3%, p = 0.038), mainly due to a significant reduction of IPT in the intermediate risk group. IPT rates in the high-risk group remained stable over time. Conclusion Appropriate clinical implementation of NIPT is still currently a challenge for prenatal medicine experts. Our data suggest that widespread uptake of NIPT is becoming more common these days; however, a contingent approach might prevent redundant uptake.

Controversies in implementing non-invasive prenatal testing in a public antenatal care program

Women's autonomy and an inclusive society for all individuals are highly valued in Norway. The Norwegian Biotechnology Act changed in 2020 allowing first-trimester screening and cell-free DNA for common trisomies to all pregnant women. However, implementing non-invasive prenatal testing (NIPT) in a public antenatal care program is difficult, because many patients, politicians, and medical professionals do not consider trisomy 21 a severe medical disease. Screening for trisomies at an early gestation might inevitably lead to an increase in pregnancy terminations and making cost-benefit calculations is ethically challenging. Moreover, offering NIPT to all pregnant women is debatable because of the lower prevalence of fetal trisomies in younger women. Therefore, appropriate genetic pre-test counseling is essential. Furthermore, organizing the service between private institutions and public hospitals poses another debate and challenges both quality and equal access to health services for women across the country.

Society for Maternal-Fetal Medicine Special Statement: Checklist for pregnancies resulting from in vitro fertilization

The management of pregnancies resulting from in vitro fertilization includes several recommended interventions at various times by various providers. To minimize the chance of errors of omission, the Society for Maternal-Fetal Medicine presents a patient-oriented checklist summarizing the recommended management of such pregnancies.

Society for Maternal-Fetal Medicine Consult Series #57: Evaluation and management of isolated soft ultrasound markers for aneuploidy in the second trimester: (Replaces Consults #10, Single umbilical artery, October 2010; #16, Isolated echogenic bowel diagnosed on second-trimester ultrasound, August 2011; #17, Evaluation and management of isolated renal pelviectasis on second-trimester ultrasound, December 2011; #25, Isolated fetal choroid plexus cysts, April 2013; #27, Isolated echogenic intracardiac focus, August 2013)

Soft markers were originally introduced to prenatal ultrasonography to improve the detection of trisomy 21 over that achievable with age-based and serum screening strategies. As prenatal genetic screening strategies have greatly evolved in the last 2 decades, the relative importance of soft markers has shifted. The purpose of this document is to discuss the recommended evaluation and management of isolated soft markers in the context of current maternal serum screening and cell-free DNA screening options. In this document, "isolated" is used to describe a soft marker that has been identified in the absence of any fetal structural anomaly, growth restriction, or additional soft marker following a detailed obstetrical ultrasound examination. In this document, "serum screening methods" refers to all maternal screening strategies, including first-trimester screen, integrated screen, sequential screen, contingent screen, or quad screen. The Society for Maternal-Fetal Medicine recommends the following approach to the evaluation and management of isolated soft markers: (1) we do not recommend diagnostic testing for aneuploidy solely for the evaluation of an isolated soft marker following a negative serum or cell-free DNA screening result (GRADE 1B); (2) for pregnant people with no previous aneuploidy screening and isolated echogenic intracardiac focus, echogenic bowel, urinary tract dilation, or shortened humerus, femur, or both, we recommend counseling to estimate the probability of trisomy 21 and a discussion of options for noninvasive aneuploidy screening with cell-free DNA or quad screen if cell-free DNA is unavailable or cost-prohibitive (GRADE 1B); (3) for pregnant people with no previous aneuploidy screening and isolated thickened nuchal fold or isolated absent or hypoplastic nasal bone, we recommend counseling to estimate the probability of trisomy 21 and a discussion of options for noninvasive aneuploidy screening through cell-free DNA or quad screen if cell-free DNA is unavailable or cost-prohibitive or diagnostic testing via amniocentesis, depending on clinical circumstances and patient preference (GRADE 1B); (4) for pregnant people with no previous aneuploidy screening and isolated choroid plexus cysts, we recommend counseling to estimate the probability of trisomy 18 and a discussion of options for noninvasive aneuploidy screening with cell-free DNA or quad screen if cell-free DNA is unavailable or cost-prohibitive (GRADE 1C); (5) for pregnant people with negative serum or cell-free DNA screening results and an isolated echogenic intracardiac focus, we recommend no further evaluation as this finding is a normal variant of no clinical importance with no indication for fetal echocardiography, follow-up ultrasound imaging, or postnatal evaluation (GRADE 1B); (6) for pregnant people with negative serum or cell-free DNA screening results and isolated fetal echogenic bowel, urinary tract dilation, or shortened humerus, femur, or both, we recommend no further aneuploidy evaluation (GRADE 1B); (7) for pregnant people with negative serum screening results and isolated thickened nuchal fold or absent or hypoplastic nasal bone, we recommend counseling to estimate the probability of trisomy 21 and discussion of options for no further aneuploidy evaluation, noninvasive aneuploidy screening through cell-free DNA, or diagnostic testing via amniocentesis, depending on clinical circumstances and patient preference (GRADE 1B); (8) for pregnant people with negative cell-free DNA screening results and isolated thickened nuchal fold or absent or hypoplastic nasal bone, we recommend no further aneuploidy evaluation (GRADE 1B); (9) for pregnant people with negative serum or cell-free DNA screening results and isolated choroid plexus cysts, we recommend no further aneuploidy evaluation, as this finding is a normal variant of no clinical importance with no indication for follow-up ultrasound imaging or postnatal evaluation (GRADE 1C); (10) for fetuses with isolated echogenic bowel, we recommend an evaluation for cystic fibrosis and fetal cytomegalovirus infection and a third-trimester ultrasound examination for reassessment and evaluation of growth (GRADE 1C); (11) for fetuses with an isolated single umbilical artery, we recommend no additional evaluation for aneuploidy, regardless of whether results of previous aneuploidy screening were low risk or testing was declined. We recommend a third-trimester ultrasound examination to evaluate growth and consideration of weekly antenatal fetal surveillance beginning at 36 0/7 weeks of gestation (GRADE 1C); (12) for fetuses with isolated urinary tract dilation A1, we recommend an ultrasound examination at ≥32 weeks of gestation to determine if postnatal pediatric urology or nephrology follow-up is needed. For fetuses with urinary tract dilation A2-3, we recommend an individualized follow-up ultrasound assessment with planned postnatal follow-up (GRADE 1C); (13) for fetuses with isolated shortened humerus, femur, or both, we recommend a third-trimester ultrasound examination for reassessment and evaluation of growth (GRADE 1C).

Clinical Significance of Non-Invasive Prenatal Screening for Trisomy 7: Cohort Study and Literature Review

Trisomy 7 is the most frequently observed type of rare autosomal trisomies in genome-wide non-invasive prenatal screening (NIPS). Currently, the clinical significance of trisomy 7 NIPS-positive results is still unknown. We reviewed two independent cohorts from two laboratories where similar NIPS metrics were applied. A total of 70,441 singleton cases who underwent genome-wide NIPS were analyzed, among which 39 pregnancies were positive for trisomy 7, yielding a screen-positive rate of 0.055% (39/70,441). There were 28 cases with invasive testing results available; the positive predictive value (PPV) was 3.6% (1/28). We then searched the published NIPS studies to generate a large cohort of 437,873 pregnancies and identified 247 cases (0.056%) that were screened positive for trisomy 7. The overall PPV was 3.4% (4/118) in the combined data. The presence of uniparental disomy 7 was not detected in the NIPS trisomy 7-positive pregnancies with normal fetal karyotype. Among the 85 cases with pregnancy outcome available in combined data, 88.2% were normal live births, 14.1% had intrauterine growth restriction, preterm birth or low birth weight, 3.5% presented with ultrasound abnormality, and no fetal loss was observed. Our data provide valuable information for counseling and management of trisomy 7-positive NIPS pregnancies.

The personal utility of cfDNA screening: Pregnant patients' experiences with cfDNA screening and views on expanded cfDNA panels

Prenatal cell-free DNA screening (cfDNA) provides more genetic risk information about the fetus than has ever been possible. At the same time, the rapid expansion of new cfDNA panels raises important questions about how to structure patient-centered discussions that best support patients' decision-making about its use. To address this question, we conducted interviews with pregnant patients to identify decision-making needs and preferences with respect to cfDNA in patient-centered healthcare discussions, given its evolving capability to identify a range of fetal variants. Personal utility was a core concept guiding decision-making. Participants spoke of how their deeply personal values and beliefs about maternal responsibility, actionability, and tolerance of uncertainty framed their view of the personal utility of cfDNA screening. While discussing their notions of personal utility with their healthcare provider, participants also had concerns about potential ramifications for the provider-patient relationship and shared decision-making when disclosing values and preferences regarding disability, quality of life, and termination-particularly as it becomes possible to identify variants with different disease-associated severity and outcomes. The complexities associated with the introduction of genomics in prenatal care present unique challenges to structuring effective shared decision-making discussions between patients and their healthcare providers. While efforts are underway to determine how to best educate patients about the medical aspects of cfDNA, it is equally important to develop approaches in healthcare communication that enable patients to make informed, values-based decisions about the use of cfDNA and its impact on their pregnancy.

Current landscape of prenatal genetic screening and testing

Pregnant patients should be offered the option of prenatal genetic screening and diagnostic testing. The type of screening and testing offered to a patient may depend on various factors including but not limited to age, family history, fetal findings, exposures, and patient preferences. Prenatal screening is available for a variety of genetic conditions including aneuploidy, congenital abnormalities, and carrier status. Diagnostic testing options include karyotype, prenatal microarray, as well as next-generation sequencing. The various options differ in methodology, accuracy, timing and indication for testing, and information they provide. Given that the technologies related to prenatal testing are rapidly evolving and improving, the array of available screening and testing modalities are increasing. This article reviews the current offerings in prenatal screening and diagnosis.

Utility of ultrasound examination at 10-14 weeks prior to cell-free DNA screening for fetal aneuploidy

OBJECTIVE

To estimate the frequency of unexpected first-trimester ultrasound findings that would alter prenatal management in pregnant women eligible for cell-free (cf) DNA screening because of advanced maternal age (AMA).

METHODS

This was a retrospective cohort study of all AMA women at a tertiary care center who had a 10-14-week ultrasound examination between 1 January 2012 and 27 April 2015. Information on pregnancy dating, obstetric ultrasound examination, prenatal screening and genetic testing were collected from a perinatal database. The primary outcome was an unexpected ultrasound finding in the first trimester that would alter the prenatal screening/testing strategy.

RESULTS

In total, 2337 women met the inclusion criteria, with a total of 2462 fetuses. Sixty-eight (2.9%) women had an anomalous fetus, of which 44 (64.7%) had diagnostic testing. In the entire cohort, a non-viable pregnancy was identified in 153 (6.5%) women. Multiple gestation was identified in 32 (1.4%) women; five had a cotwin demise. Gestational dating was revised for 126 (5.4%) women. Among those who opted for aneuploidy screening (n = 1806), 68.5% had cfDNA screening and 31.5% had first-trimester screening by analysis of maternal serum biomarkers and nuchal translucency thickness. Among those eligible for cfDNA screening, 16.1% (95% CI, 15.0-18.0%; 377/2337) had an ultrasound finding (anomaly, incorrect dating, multiple gestation, non-viable pregnancy) at the time of testing that would have altered the provider's counseling regarding the prenatal screening/testing strategy.

CONCLUSIONS

A substantial proportion of AMA women eligible for cfDNA screening have fetal ultrasound findings that could alter genetic testing strategy and clinical management. This study recommends ultrasound examination prior to cfDNA screening in AMA women. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Obesity and cell-free DNA "no calls": is there an optimal gestational age at time of sampling?

BACKGROUND

Cell-free DNA screen failures or "no calls" occur in 1-12% of samples and are frustrating for both clinician and patient. The rate of "no calls" has been shown to have an inverse relationship with gestational age. Recent studies have shown an increased risk for "no calls" among obese women.

OBJECTIVE

We sought to determine the optimal gestational age for cell-free DNA among obese women.

STUDY DESIGN

We performed a retrospective cohort study of women who underwent cell-free DNA at a single tertiary care center from 2011 through 2016. Adjusted odds ratios with 95% confidence intervals for a "no call" were determined for each weight class and compared to normal-weight women. The predicted probability of a "no call" with 95% confidence intervals were determined for each week of gestation for normal-weight and obese women and compared.

RESULTS

Among 2385 patients meeting inclusion criteria, 105 (4.4%) had a "no call". Compared to normal-weight women, the adjusted odds ratio of a "no call" increased with increasing weight class from overweight to obesity class III (respectively: adjusted odds ratio, 2.31; 95% confidence interval, 1.21-4.42 to adjusted odds ratio, 8.55; 95% confidence interval, 4.16-17.56). A cut point at 21 weeks was identified for obesity class II/III women at which there is no longer a significant difference in the probability of a "no call" for obese women compared to normal weight women. From 8-16 weeks, there is a 4.5% reduction in the probability of a "no call" for obesity class II/III women (respectively: 14.9%; 95% confidence interval, 8.95-20.78 and 10.4%; 95% confidence interval, 7.20-13.61; P_trend < .01).

CONCLUSION

The cut point of 21 weeks for optimal sampling of cell-free DNA limits reproductive choices. However, a progressive fall in the probability of a "no call" with advancing gestational age suggests that delaying cell-free DNA for obese women is a reasonable strategy to reduce the probability of a "no call".

The role of ultrasound in women who undergo cell-free DNA screening

The introduction of cell-free DNA screening for aneuploidy into obstetric practice in 2011 revolutionized the strategies utilized for prenatal testing. The purpose of this document is to review the current data on the role of ultrasound in women who have undergone or are considering cell-free DNA screening. The following are Society for Maternal-Fetal Medicine recommendations: (1) in women who have already received a negative cell-free DNA screening screen, ultrasound at 11-14 weeks of gestation solely for the purpose of nuchal translucency measurement (Current Procedural Terminology code 76813) is not recommended (grade 1B); (2) we recommend that diagnostic testing should not be recommended to patients solely for the indication of an isolated soft marker in the setting of a negative cell-free DNA screen (grade 2B); (3) in women with an isolated soft marker without other clinical implications (ie, choroid plexus cyst or echogenic intracardiac focus) and a negative cell-free DNA screen, we recommend describing the finding as not clinically significant or as a normal variant (grade 2B); (4) in women with an isolated soft marker that has no other clinical implication (ie, choroid plexus cyst or echogenic intracardiac focus) and a negative first- or second-trimester screening result, we recommend describing the finding as not clinically significant or as a normal variant (grade 2B); (5) we recommend that all women in whom a structural abnormality is identified by ultrasound should be offered diagnostic testing with chromosomal microarray (grade 1A); and (6) we recommend against routine screening for microdeletions with cell-free DNA screening (grade 1B).

Cell-free DNA vs sequential screening for the detection of fetal chromosomal abnormalities

BACKGROUND

Sequential and cell-free DNA (cfDNA) screening are both tests for the common aneuploidies. Although cfDNA has a greater detection rate (DR) for trisomy 21, sequential screening also can identify risk for other aneuploidies. The comparative DR for all chromosomal abnormalities is unknown.

OBJECTIVE

To compare sequential and cfDNA screening for detection of fetal chromosomal abnormalities in a general prenatal cohort.

STUDY DESIGN

The performance of sequential screening for the detection of chromosome abnormalities in a cohort of patients screened through the California Prenatal Screening Program with estimated due dates between August 2009 and December 2012 was compared with the estimated DRs and false-positive rates (FPRs) of cfDNA screening if used as primary screening in this same cohort. DR and FPR for cfDNA screening were abstracted from the published literature, as were the rates of "no results" in euploid and aneuploid cases. Chromosome abnormalities in the entire cohort were categorized as detectable (trisomies 13, 18, and 21, and sex chromosome aneuploidy), or not detectable (other chromosome abnormalities) by cfDNA screening. DR and FPR were compared for individual and all chromosome abnormalities. DR and FPR for the cohort were compared if "no results" cases were considered "screen negative" or "screen positive" for aneuploidy. DR and FPR rates were compared by use of the Fisher exact test.

RESULTS

Of 452,901 women who underwent sequential screening during the time period of the study, 2575 (0.57%) had a fetal chromosomal abnormality; 2101 were detected for a DR of 81.6%, and 19,929 euploid fetuses had positive sequential screening for an FPR rate of 4.5%. If no results cases were presumed normal, cfDNA screening would have detected 1820 chromosome abnormalities (70.7%) with an FPR of 0.7%. If no results cases were considered screen positive, 1985 (77.1%) cases would be detected at a total screen positive rate of 3.7%. In either case, the detection rate of sequential screening for all aneuploidies in the cohort was greater than cfDNA (P<.0001).

CONCLUSION

For primary population screening, cfDNA provides lower DR than sequential screening if considering detection of all chromosomal abnormalities. Assuming that no results cfDNA cases are high-risk improves cfDNA detection but with a greater FPR. cfDNA should not be adopted as primary screening without further evaluation of the implications for detection of all chromosomal abnormalities and how to best evaluate no results cases.