The diagnostic value of a detailed first trimester anomaly scan in fetuses with increased nuchal translucency thickness

A Pain in the Neck: Lessons Learnt from Genetic Testing in Fetuses Detected with Nuchal Fluid Collections, Increased Nuchal Translucency versus Cystic Hygroma-Systematic Review of the Literature, Meta-Analysis and Case Series

Fetal Nuchal fluid collections can manifest with two distinct presentations attributable to the same phenotypic spectrum: increased nuchal translucency (iNT) and cystic hygroma. The prenatal detection of these findings should prompt an accurate assessment through genetic counseling and testing, including karyotype, chromosomal microarray analysis (CMA) and multigene RASopathy panel. We performed a systematic review of the literature and meta-analysis, to calculate diagnostic yields of genetic testing in fetuses with iNT and cystic hygroma. We compared the results with a cohort of 96 fetuses with these isolated findings. Fetuses with isolated NT ≥ 2.5 mm showed karyotype anomalies in 22.76% of cases and CMA presented an incremental detection rate of 2.35%. Fetuses with isolated NT ≥ 3 mm presented aneuploidies in 14.36% of cases and CMA had an incremental detection rate of 3.89%. When the isolated NT measured at least 3.5 mm the diagnostic yield of karyotyping was 34.35%, the incremental CMA detection rate was 4.1%, the incremental diagnostic rate of the RASopathy panel was 1.44% and it was 2.44% for exome sequencing. Interestingly, CMA presents a considerable diagnostic yield in the group of fetuses with NT ≥ 3.5 mm. Similarly, exome sequencing appears to show promising results and could be considered after a negative CMA result.

First-Trimester Nonvisualization of the Parotid Gland and Aneuploidy in Fetuses With Increased Nuchal Translucency: A Prospective Cohort Study

OBJECTIVES

Aplasia and hypoplasia of the major salivary glands, particularly the parotid glands, were reported to be associated with trisomy 21. This study aimed to evaluate the value of first-trimester nonvisualization of the parotid gland in a high-risk population of fetuses with increased nuchal translucency (NT).

METHODS

A single-center prospective observational cohort study was conducted. The feasibility of imaging the parotid gland was assessed in 100 sequential cases of routine low-risk NT scans. In a 2-dimensional image in an axial plane at the level of the fetal mandible, the parotid glands appear as bilateral hyperechoic round areas. Cases referred for counseling for an NT measured above the 95th percentile for gestational age were evaluated for visualization of the parotid glands. Prenatal findings were correlated with fetal genetic analysis results.

RESULTS

Forty-two cases with increased NT constituted the final study group. Within the group with nonvisualization of the parotid gland, genetic testing revealed 9 cases of trisomy 21, 3 cases of trisomy 18, and 1 case of monosomy X. The sensitivity and specificity of nonvisualization of the parotid gland as a predictor of aneuploidy were 76% and 80%, respectively. The positive likelihood ratio, negative likelihood ratio, and relative risk were 3.82 (95% confidence interval [CI], 1.67-8.74), 0.29 (95% CI, 0.12-0.71), and 4.33 (95% CI, 1.69-11.09; P < .01). The negative predictive value was 95.14%.

CONCLUSIONS

First-trimester nonvisualization of the parotid gland may constitute a potential method for detection of aneuploid fetuses within a high-risk population.