OC06.06: Management and outcomes following anomalous findings at the pre‐NIPT ultrasound

To evaluate the clinical utility of the pre-NIPT scan at 10-14 weeks gestation in singleton pregnancies and examine the genetic and structural outcomes in those with anomalous pre-NIPT ultrasound findings in a cohort undertaking definitive prenatal testing. Pre-NIPT scans in 902 patients with prenatal microarray testing were classified into 5 groups: (I) structural abnormality; (II) septated NT enlargement; (III) generalised edema; (IV) NT > 95th centile without generalised edema and (V) no abnormality detected. For each pre-NIPT group, aneuploidy was identified in 61% (I), 54% (II), 48% (III) and 44% (IV). Similar rates of genetic abnormality were found in early and late pre-NIPT scans (CRL < or > 45 mm). Structural abnormalities not identified at the pre-NIPT scan were found in 57 cases at the later first trimester scan which changed management for those with low-risk NIPT results. NT measurement above the 95th centile at 10-11 weeks (2.2 mm) was associated with aneuploidy in 48% and if the NT enlargement progressed above 3.5mm at a later 11-14 week scan, the rate of aneuploidy increased to 55%. Most microdeletion cases do not have a significant pre-NIPT finding. The high incidence of genetic abnormality identified after an abnormal pre-NIPT scan justifies bypassing NIPT screening in favour of offering CVS. Combining gwNIPT with a 12-13 week ultrasound to review NT measurement and fetal structural assessment provides valuable additional information without increasing the risk of missing triploidy or genetic abnormalities currently not detected by gwNIPT.