A Rare Case of Microduplication on Chromosome 13 Detected as High Risk for Trisomy 13 on NIPT Screening

Abstract Noninvasive prenatal testing (NIPT) has revolutionized the screening methods for fetal chromosomal aneuploidies with high utility for aneuploidies for common chromosomes 13,18, 21, X and Y. Trisomy 13 is often associated with major and minor fetal malformations and can be screened by antenatal fetal scan and first- and second-trimester biochemical screening. We describe a case with high risk for trisomy 13 on NIPT, but without any fetal abnormalities on fetal scan. As recommended, follow-up invasive testing of amniotic fluid by chromosomal microarray detected a microduplication on chromosome 13, which has been associated with congenital microcoria. This case demonstrates the high sensitivity and clinical utility of NIPT in detecting rare copy number variations, which can assist families in making informed reproductive decisions. This also emphasizes that all screen positive NIPT cases should be confirmed with an appropriate diagnostic test by an invasive method.