The importance of ultrasound preceding cell-free DNA screening for fetal chromosomal abnormalities

This study aims to determine the incidence of ultrasound findings that may change clinical management on the day of blood-sampling for cell-free DNA (cfDNA) screening.

A retrospective study was conducted at a tertiary provider of obstetric and gynecological ultrasound in Melbourne, Australia. Individual patient files were reviewed and results were collated for maternal characteristics, pre-cfDNA ultrasound reports, results and test characteristics of both cfDNA and diagnostic testing, and genetic counselling notes. The primary outcome was a potential change in patient management due to findings detected on the pre-cfDNA ultrasound.

Of 6250 pre-cfDNA ultrasounds, 6207 were included in analysis. Of these, 598 (9.6%) pregnancies had a finding on pre-cfDNA ultrasound that had the potential to change management. The reasons for this potential change in management were detection of gestational age below 10 weeks (245, 3.9%), miscarriage (175, 2.8%), demised twin (43, 0.7%), fetal edema (115, 1.9%) and major structural abnormalities (20, 0.3%). These findings were more common in patients of advanced maternal age and in spontaneous conceptions.

An ultrasound prior to cfDNA screening has the potential to change clinical management in almost one in 10 women. The proportion is higher in older age groups and lower in IVF-conceived pregnancies.