Discordant circulating fetal DNA and subsequent cytogenetics reveal false negative, placental mosaic, and fetal mosaic cfDNA genotypes

Abstract

These Maternal Fetal Medicine referrals demonstrate that positive NIPT results identify an increased abnormal karyotypic frequency as well as a substantial proportion of discordant fetal results. Our results found: (1) a normal NIPT test result followed by a 20 week anatomical ultrasound detected a false negative trisomy 18 NIPT result, (2) a substantial proportion of abnormal NIPT tests identify chromosomal mosaicism that may or may not be confined to the placenta, (3) follow up karyotyping should be completed on the newborn placenta and peripheral blood when the amniocyte karyotype does not confirm the NIPT reported abnormality in order to identify ongoing risk of developing mosaic symptoms, and (4) karyotyping all high risk fetuses tested by amniocentesis defines the 24% of chromosome abnormalities not currently screened by NIPT.