51 - Triploidy in a Live-Born Female With Normal Non-Invasive Prenatal Testing Results

Abstract

Non-invasive prenatal testing (NIPT) has become an increasingly popular option for pregnancies with abnormal ultrasound (U/S) findings. Although it has high clinical sensitivity and specificity for trisomy 21, some other, rarer cytogenetic conditions are less likely to be detected with certain NIPT methods. Triploidy is a rare genetic condition that usually results in miscarriage or stillbirth. Very few triploid pregnancies result in a live birth. We present a case of a female neonate with multiple anomalies and normal non-invasive testing who was diagnosed with dygynic triploidy after birth. Fetal U/S at 19 weeks was abnormal for a two-vessel cord, a cardiac defect and intrauterine growth restriction (IUGR). NIPT at 20w indicated a normal female result. Due to the abnormal U/S findings, further diagnostic testing was recommended but parents declined amniocentesis due to normal NIPT. Subsequent U/S at 30w identified anomalies including IUGR, a congenital heart defect, cerebellar hypoplasia, thoracic hemivertebrae, absent right kidney, absent left hand, right hand syndactyly and abnormal posturing of the hands and feet. The patient was born at 33 weeks gestation by C-section due to severe IUGR and fetal distress. She had additional anomalies including small posterior fossa, atrial septal defect, pulmonary hypoplasia, toe syndactyly, cutis aplasia and cleft palate. She had respiratory distress requiring mechanical ventilation. She developed bilateral pneumothoraces and progressive respiratory failure and died after 3 days. Direct FISH and cytogenetic analysis revealed a female triploid karyotype. The NIPT method used (InformaSeq) is used by many laboratories and is unable detect triploidy. This case highlights the need for more sensitive NIPT methods for detecting non-trisomic abnormal cytogenetic findings. In the context of MCA and normal NIPT, amniocentesis and karyotype and/or CMA should be recommended for families that desire diagnostic testing.