Repeat measurements of nuchal translucency at 11-14 weeks of gestation: when do we need them?

SIGNIFICANCE OF LOW MATERNAL SERUM Β-HCG LEVELS IN THE ASSESSMENT OF THE RISK OF ATYPICAL CHROMOSOMAL ABNORMALITIES

INTRODUCTION

The introduction of prenatal cell-free DNA as a screening test has surpassed traditional combined first-trimester screening (cFTS) in the detection of common trisomies. However, its current limitation in detecting only common trisomies is affecting the diagnostic yield for other clinically significant chromosomal abnormalities.

METHODS

In efforts to optimize the detection of fetuses with genetic abnormalities, we have analyzed the relationship between the cFTS risk score and biomarkers with atypical chromosomal abnormalities. Furthermore, we have evaluated the impact of prenatal cell-free DNA screening on the detection of chromosomal abnormalities in our population. For these purposes, we performed a retrospective study of 877 singleton pregnancies who underwent chromosomal microarray analysis (CMA) between 2013 to 2020 and for whom first-trimester screening data were available.

RESULTS

The results demonstrated that low levels of free beta human chorionic gonadotropin (β-hCG) (≤ 0.37 MoM) and increased fetal nuchal translucency (NT) (≥ 3.5mm) were statistically associated with the presence of atypical chromosomal abnormalities. In fact, the risk of pathogenic CMA results increased from 6% to 10% when fetal NT was increased and from 6% to 20% when a low serum β-hCG level was detected in the high-risk cFTS group. Moreover, our results showed that altered serum levels of β-hCG can have a substantial impact on the early detection of clinically relevant copy number variants.

DISCUSSION/CONCLUSION

Traditional cFTS can potentially identify a substantial proportion of atypical chromosomal aberrations, and women with increased NT or low maternal serum β-hCG levels are at increased risk of having pathogenic CMA results. Our results may help clinicians and women decide whether invasive testing or prenatal cell-free DNA screening testing are more appropriate for each situation.

[A simple self-assessment tool for the first-trimester ultrasound images]

OBJECTIVES

The objective of this study was to establish a minimum subset of simple criteria for the self-assessment of the quality of first-trimester ultrasound images of nuchal translucency (NT) and crown-rump length (CRL).

METHODS

We designed 162 simplified image-scoring methods (ISM) based on 1, 2, 3 or 4 binary criteria derived from the 8 criteria of the original image scoring method of the French College of Fetal Ultrasound (CFEF). These ISM were assessed on 68,250 consecutive scans of the French national audit conducted by the CFEF on NT and CRL images. The ISM associated with the best precision to identify excellent/reasonable quality scans were selected.

RESULTS

Simplified ISM based on 1, 2, 3 and 4 criteria showed maximum positive predictive values of 95.3% (95.11-95.50) 98.0% (97.87-98.14), 99.3% (99.17-99.35) and 99.7% (99.68-99.79), respectively, to identify excellent/reasonable quality scans. The proportion of excellent/reasonable scans was 2.8 to 16.7% when three criteria among the 8 were insufficient, and 0.17 to 3.95% when four criteria were insufficient.

CONCLUSIONS

The best performing ISM was based on the following four quality criteria: (i) sagittal plane of the NT, (ii) calipers placement for measuring the NT, (iii) image magnification of NT images and (iv) CRL measurement. This score might be the most relevant in clinical practice in the first-trimester screening.