Usefulness of early morphological ultrasound in association with cell-free DNA testing in case of atypical serum markers in first trimester of pregnancy: A retrospective study over 5 years

Background: Early morphologic ultrasound, generally carried out in case of atypical first trimester serum markers (PAPP-A and/or free hCG beta <0.30 MoM), has not been re-evaluated since the possibility of performing a cell -free fetal DNA analysis in this indication. Our objective was to evaluate the usefulness of early morphological ultrasound in case of atypical profile of serum markers performed in association with Non -Invasive Prenatal Testing (NIPT). Methods: This was a single -center retrospective study in a tertiary maternity. Between January 2017 and December 2021, women with an atypical first trimester serum markers and low/intermediate risk for trisomy 21 (<1/50) were included. The clinical data, results of first trimester serum markers, NIPT, early morphological ultrasound and subsequent ultrasounds and other investigations (amniocentesis, pregnancy outcomes) were analyzed. Results: After exclusion of women with high -risk of trisomy 21 and lost to follow-up, 163 women were included. In 72 % of cases (117/163), women had a low risk of trisomy 21, and 39 % (59/163) had an early morphological ultrasound. Early morphological ultrasound was useful to detect severe IUGR leading to the suspicion of triploidy (3/163, 1.8 %). In all other situations, it did not allow earlier management. After analysis of the 3 triploidy cases, a collapsed profile for both serum markers was demonstrated (<0.25 MoM). Conclusions: Systematic early morphological ultrasound in case of an atypical serum marker profile seems useless considering the performance of NIPT. An ultrasound restricted to women with both markers below 0.25 MoM would allow the early detection of triploidy.