The performance of an intermediate 16th-week ultrasound scan for the follow-up of euploid fetuses with increased nuchal translucency

First-Trimester Ultrasound Screening in Routine Obstetric Practice

Technologic advances and ultrasonographer-physician experience in fetal imaging have led to significant improvements in our ability to distinguish between normal and abnormal fetal structural development in the latter part of the first trimester. As a critical component of pregnancy care, assessment of fetal anatomy at the end of the first trimester with a standardized imaging protocol should be offered to all pregnant patients regardless of aneuploidy screening results because it has been demonstrated to identify approximately half of fetal structural malformations. Early identification of abnormalities allows focused genetic counseling, timely diagnostic testing, and subspecialist consultation. In addition, a normal ultrasound examination result offers some degree of reassurance to most patients. Use of cell-free DNA alone for aneuploidy screening while foregoing an accompanying early anatomic evaluation of the fetus will result in many anomalies that are typically detected in the first trimester not being identified until later in pregnancy, thus potentially diminishing the quality of obstetric care for pregnant individuals and possibly limiting their reproductive options, including pregnancy termination.

[Management of isolated increased nuchal translucency: survey among the Pluridisciplinary Centers for Prenatal Diagnosis]

OBJECTIVES

The management for isolated increased nuchal translucency (NT) in the first trimester with a normal karyotype and normal Chromosomal Microarray Analysis (CMA) is not consensual. The aim was to perform a survey among the Pluridisciplinary Centers for Prenatal Diagnosis (CPDPN) in France regarding their management of increased NT in the first trimester.

METHODS

We conducted a multicenter descriptive survey between September 2021 and October 2021 among the 46 CPDPNs of France.

RESULTS

The response rate was 56.5% (n = 26/46). The NT thickness threshold for which invasive diagnosis testing is performed is 3.0mm in 23.1% of centers (n = 6/26) and 3.5mm in 76.9% of centers (n = 20/26). A CMA was performed alone in 26.9% of centers (n = 7/26) while 7.7% of centers (n = 2/26) did not perform a CMA. The gestational age for the first reference ultrasound scan was 16 to 18 WG in 88.5% of centers (n = 23/26), while it was not performed before 22 WG in 11.5% of centers (n = 3/26). Fetal echocardiography is proposed systematically in 73.1% of centers (n = 19/26).

CONCLUSION

There is heterogeneity in the management of increased NT in the first trimester among the CPDPNs in France. In case of increased NT on first trimester ultrasound scan, the NT thickness threshold for which invasive diagnosis testing is performed varies from 3.0 mm or 3.5mm depending on the center. Moreover, CMA and early reference morphological ultrasound scan between 16 and 18 WG were not systematically performed, despite the current data suggesting their interest.

Extending the prenatal Noonan's phenotype by review of ultrasound and autopsy data

OBJECTIVES

The antenatal phenotypic spectrum of Noonan Syndrome (NS) requires better characterization.

METHODS

This multicenter retrospective observational included 16 fetuses with molecularly confirmed NS admitted for fetopathological examination between 2009 and 2016.

RESULTS

Among 12 pathogenic variants (PV) in PTPN11 (80%), 5 (42%) fell between position c.179 and c.182. Ultrasound showed increased nuchal translucency (n=13/16, 93%), increased nuchal fold after 15 weeks of gestation (n=12/16, 75%), pleural effusions (n=11/16, 69%), polyhydramnios (n=9/16, 56%), hydrops (n=7/16, 44%), cardiovascular (n=6/16, 38%) and cerebral (n=4/16, 25%) anomalies. Fetopathological examination found dysmorphic features in all cases, cardiovascular anomalies (n=12/15, 80%), pulmonary hypoplasia (n=10/15, 67%), effusions (n=7/15, 47%) and neuropathological anomalies (n=5/15, 33%). Hydrops was significantly (p=0.02) more frequent in the four fetuses with RIT1, NRAS and RAF1 PV versus the 12 fetuses with PTPN11 PV.

CONCLUSIONS

Increased nuchal translucency and nuchal fold is common in NS. NS antenatal phenotype showed high in utero fetal death, hydrops, prenatal pleural effusion and pulmonary hypoplasia, although the inclusion of only deceased fetuses will have selected more severe phenotypes. Non-specific cardiovascular and neurological abnormalities should be added to NS antenatal phenotype. Next generation sequencing will help detect more genotypes, clarifying the prenatal phenotype and identifying genotype-phenotype correlations. This article is protected by copyright. All rights reserved.

The 16-week sonographic findings in fetuses with increased nuchal translucency and a normal array

OBJECTIVE

The aim of this prospective study is to evaluate the performance of the intermediate 16-week ultrasound in fetuses with increased nuchal translucency (NT) and a normal chromosomal microarray analysis (CMA).

METHODS

During a one-year period, a detailed ultrasound was performed at 16 week' gestation for patients with an increased NT (≥3.5 mm) and normal CMA. Pregnancy work-up included a traditional 22-week ultrasound scan, an echocardiography, and the option of a 10-gene Rasopathy panel after a normal 16-week scan. Abnormal findings and pregnancy outcomes were collected and analyzed.

RESULTS

In 52 fetuses with an isolated increased NT and normal CMA, 14 (26.5%) were noted to have structural defects on the 16-week ultrasound. Intrauterine fetal death occurred in one (1.9%) case identified by the 16-week scan. Of the remaining 37 cases, six opted for a RASopathy panel. In this group, one case of Noonan syndrome was detected. One case of unilateral duplex kidney had not been found until the 22-week scan. One case of fetal growth restriction was identified in the third trimester. The remaining 34 cases proceeded with normal ultrasound to term.

CONCLUSION

The 16-week ultrasound scan performed on fetuses with increased NT and normal CMA could detect the majority of structural abnormalities that are expected to be identified traditionally at 20-24 weeks.

Different Cutoff Values for Increased Nuchal Translucency in First-Trimester Screening to Predict Fetal Chromosomal Abnormalities

INTRODUCTION

Increased nuchal translucency (NT) is closely related to an increased risk of chromosomal abnormalities. However, the criterion of increased NT for invasive prenatal diagnosis remains controversial, as the cutoff values are inconsistent among countries. This study was conducted to compare the various cutoff values of increased NT and calculate the incidence of chromosomal abnormalities to determine the predictive ability of these cutoff values in conventional chromosome analysis.

METHODS

A total of 3223 invasive samples with increased nuchal translucency (NT) or other non-ultrasound indications were collected from singleton pregnant women. Samples with isolated increased NT were divided into five groups based on the NT thickness: 909 samples in the NT ≥2.5 mm group, 819 samples in the NT ≥95th group, 547 samples in the NT ≥99th group, 527 samples in the NT ≥3.0 mm group, and 253 samples in the NT ≥3.5 mm group; 2301 samples with normal NT were considered as the control group. All five groups were karyotyped and the results were compared. The accuracy of the NT cutoff value for the screening of chromosomal abnormalities was assessed using receiver operating characteristic curve analysis.

RESULTS

Detection of all chromosomal aberrations and trisomy 21 showed that the sensitivity and false-positive rate decreased sequentially in the NT ≥2.5 mm, NT ≥95th, NT ≥3 mm, NT ≥99th, and NT ≥3.5 mm groups, whereas the specificity, positive predictive value, and false-negative rates increased sequentially. Comprehensive analysis of various factors, including sensitivity and specificity, revealed values equal to or higher than the calculated 95th percentile of NT distribution, which showed a sensitivity of 49.2% and specificity of 75.67% for detecting all aneuploidies and a sensitivity of 64% and specificity of 75.45% for trisomy 21, exhibiting the highest ability for the screening of chromosomal defects in first-trimester screening.

CONCLUSION

For different thresholds of NT thickness, values equal to or higher than the calculated 95th percentile of the NT distribution showed the highest ability for the screening of chromosomal defects in first-trimester screening.

Evaluation of the Scan Duration and Mechanical and Thermal Indices Applied for the Diagnostic Ultrasound Examinations

OBJECTIVE

Although epidemiological studies have failed to show the harmful effects of ultrasound in humans, as a form of energy, ultrasound has the potential to cause bio-effects in tissues. Therefore, clinical guidelines have been established for ultrasound technology related to human safety, which include Thermal (TI) and mechanical (MI) indices. The appropriate TI and MI ranges for embryonic examinations are between 0-1.0 and 0-0.4, respectively. The accepted TI and MI ranges are 0-2.0 and 0-1.9, respectively, for general ultrasound examinations. In addition, the scan duration should be kept as low as possible. Therefore, the present study aimed at evaluating the scan duration, TI, and MI as measures of acoustic output during ultrasound studies.

METHODS

A cross-sectional descriptive study was conducted for patients undergoing pregnancy checkups, routine checkups, and initial diagnosis ultrasound examinations. Samples were selected from imaging departments of 4 educational hospitals based on convenience sampling and 321 checklists completed by direct observation of ultrasound examinations.

RESULTS

For pregnancy scans, the mean TI and MI were obtained as 0.32 ± 0.27 and 1.15 ± 0.13, respectively. For non-pregnancy examinations, the mean value of TI and MI were 0.30 ± 0.29 and 1.07 ± 0.35, respectively. Therefore, mean TI for pregnancy and non-pregnancy examinations and mean MI for non-pregnancy studies obtained lower than the permitted values, while the mean MI was higher than the permitted level for first trimester of pregnancy. Also, relatively suitable scan durations were seen in reviewed studies.

CONCLUSION

From this study, it may be concluded that the reported ultrasound scans were safe.

Increased nuchal translucency after low-risk noninvasive prenatal testing: What should we tell prospective parents?

Three decades ago, the observation that first trimester fetuses with excess fluid accumulation at the back of the neck were more likely to be aneuploid, gave rise to a new era of prenatal screening. The nuchal translucency (NT) measurement in combination with serum biomarkers and maternal age, resulted in the first trimester combined screening (FTCS) program. The introduction of noninvasive prenatal testing (NIPT) over the past decade has introduced the option for parents to receive highly sensitive and specific screening information for common trisomy from as early as 10 weeks gestation, altering the traditional pathway FTCS pathway. The retention of the 11-13-week NT ultrasound remains important in the detection of structural anomalies; however, the optimal management of pregnancies with a low-risk NIPT result and an isolated increased NT measurement in an era of advanced genomic testing options is a new dilemma for clinicians. For parents, the prolonged period between the initial diagnosis in first trimester, and prognostic information at each successive stage of investigations up to 22-24 weeks, can be emotionally challenging. This article addresses the common questions from parents and clinicians as they navigate the uncertainty of having a fetus diagnosed with an increased NT after a low-risk NIPT result and presents suggested approaches to management.

Microarray and RASopathy-disorder testing in fetuses with increased nuchal translucency

OBJECTIVES

To determine the incidence of chromosomal abnormalities, submicroscopic chromosomal abnormalities and RASopathy-disorder (RD) pathogenic variants in a cohort of pregnancies with nuchal translucency thickness (NT) ≥ 3.5 mm, and to propose a clinical protocol for surveillance of this group of patients.

METHODS

This was a retrospective chart review of patients referred to The Prenatal Diagnosis and Medical Genetics Program at Mount Sinai Hospital between January 2013 and December 2015, due to NT ≥ 3.5 mm, who underwent chorionic villus sampling or amniocentesis. Patients underwent extensive genetic counseling prior to invasive procedures and testing. Quantitative fluorescence polymerase chain reaction (QF-PCR) was performed as the first-line test for aneuploidy. If the result was negative, patients underwent karyotyping and/or chromosomal microarray analysis (CMA), and if the findings were normal, they had testing for RD pathogenic variants, which included nine known genes. Patients also underwent detailed fetal ultrasound examinations and echocardiography, performed by expert operators.

RESULTS

A total of 226 eligible patients were identified. In 116/226 (51.3%) patients, QF-PCR identified a chromosomal aneuploidy. The remaining 110/226 (48.7%) patients had further genetic testing. Karyotyping/CMA detected an abnormal/pathogenic cytogenetic result in 9/110 (8.2%) patients, as well as five variants of unknown significance (VOUS). RD testing yielded three pathogenic variants (3/103), giving a detection rate of 2.9%, and one VOUS. The optimal NT cut-off for RD screening was 7.9 mm in this population. In 92/110 (83.6%) patients, the genetic investigations were normal. Of these pregnancies, an early (14-16 weeks' gestation) detailed fetal ultrasound examination identified a structural abnormality in 24 (26.1%), 15 (16.3%) had an abnormal detailed ultrasound examination at 18-22 weeks' gestation and fetal echocardiography showed a cardiac abnormality in nine (9.8%). The birth outcome in the 83 pregnancies that had normal genetic investigations and known outcome included seven (8.4%) cases of termination of pregnancy, seven (8.4%) cases of intrauterine fetal death and 69 (83.1%) cases of live birth. Nine (9.8%) patients were lost to follow-up.

CONCLUSIONS

Both CMA and molecular testing for RD are important investigations in pregnancies with NT ≥ 3.5 mm. The use of genetic testing combined with fetal ultrasound examination provides valuable information that can influence pregnancy outcome, and provide recurrence risks, in this patient population. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.