EP06.03: Be aware of a diagnostic delay: Rotterdam's experience with NIPT in 1071 high-risk pregnancies

It is expected that many pregnant women will choose for NIPT instead of first trimester combined testing (ftCT). As a consequence high risk pregnancies may be identified later on in the pregnancy. NIPT performed in high risk pregnancies may lead to a diagnostic delay of some chromosome aberrations. The aim of this study was to evaluate the risk of a diagnostic delay in our cohort of high risk pregnancies tested with NIPT. 2014-2015 NIPT was performed in 1071 high risk pregnancies (risk > 1:200 after ftCT). 39 (3.6%) women subsequently chose array testing due to further doubts (10), an ultrasound anomaly found later on in the pregnancy (21) or fetal death (IUFD, 8). In 3 fetuses a pathogenic fetal unbalanced chromosome aberration matching the indication was found (isochromosome Xq, a de novo atypical 22q11 microdeletion and triploidy). Thus, in ca. 1:350 (3/1071) “false” reassurance was given with normal NIPT results and a diagnostic delay to the second trimester occurred. This is an underestimation of the overall diagnostic delay since not all unbalanced chromosome aberrations manifest ultrasound anomalies or cause IUFD. Besides this, developmental delay and intellectual disability are not immediately evident at birth. As the detection of severe chromosome disorders is more traumatic when discovered late in pregnancy and both the medical as well as psychological impact of a pregnancy termination are more severe, it is important to avoid diagnostic delay. Thus, it is of importance to identify high risk pregnancies either through searching for (new) early ultrasound markers or to offer higher resolution NIPT for all clinically significant unbalanced chromosome aberrations.