Clinical Laboratory Experience With Prenatal cfDNA Screening in Triplet Pregnancies

Abstract

Objective: Prenatal cfDNA screening is the most sensitive and specific screen for common aneuploidies in singleton and twin pregnancies and has been endorsed by several professional societies as a first-tier screen or contingent screen. However, data for triplet pregnancies is lacking, as these pregnancies are relatively uncommon and obtaining sufficient data for a robust analysis of test performance is challenging.

Method: This study presents a retrospective review of over 1500 samples from triplet pregnancies screened via cfDNA for common aneuploidies.

Results: Mean patient age was 34 years, while mean gestational age was 13 weeks. The most common indication for testing was patient age, representing > 60% of the cohort. There were 13 screen-positive cases (1.01%), 270 NR cases (17.32%), and the remainder were screen-negative. Complete or partial genetic and/or obstetric outcome information (including birth and neonatal outcomes) was available for 147 samples, including all 13 positive cfDNA samples. No false positive or false negative cases were identified.

Conclusion: The data from this study support the notion that cfDNA screening in triplet pregnancies is a reasonable approach given the lack of alternative screening options for these patients and that the performance likely approaches that of twin pregnancies, albeit with a higher no-call rate.

FIGURE 1

Indications for testing in the study cohort.

FIGURE 2

Flowchart of the samples in the study cohort. * Screen positive and screen negative rates are calculated based on reportable samples.