Objective: To investigate the performance of first-trimester screening for aneuploidies by including assessment of tricuspid blood flow in the combined test of maternal age, fetal nuchal translucency (NT) thickness, fetal heart rate (FHR) and serum free beta-human chorionic gonadotropin (beta-hCG) and pregnancy-associated plasma protein A (PAPP-A).
Method: Screening by the combined test was performed in singleton pregnancies, including 19 614 with chromosomally normal fetuses or the delivery of a phenotypically normal baby (euploid group), 122 with trisomy 21, 36 with trisomy 18, 20 with trisomy 13 and eight with Turner syndrome. In all cases tricuspid flow was assessed to determine if there was tricuspid regurgitation. We examined the performance of two screening strategies: firstly, assessment of tricuspid flow in all patients and secondly, first-stage screening using the combined test in all patients followed by second-stage assessment of tricuspid flow only in those with an intermediate risk of 1 in 51 to 1 in 1000 after the first stage.
Results: Tricuspid regurgitation was observed in 0.9% of the euploid fetuses and 55.7%, 33.3% and 30% of the fetuses with trisomies 21, 18 and 13, respectively, and in 37.5% of those with Turner syndrome. In a screening policy based on maternal age, fetal NT, FHR, serum free beta-hCG and PAPP-A, for a fixed false positive rate of 3% the standardized detection rates were 91% for trisomy 21 and 100% for trisomy 18, trisomy 13 and Turner syndrome. Assessment of tricuspid flow in all pregnancies would increase the detection rate of trisomy 21 to 96%, and the detection rates of trisomy 18, trisomy 13 and Turner syndrome would be 92%, 100% and 100%, respectively. The same detection rates were achieved with the two-stage strategy-in which it was necessary to assess tricuspid flow in only 15% of the total population-at a false positive rate of 2.4%.
Conclusions: Assessment of tricuspid flow improves the performance of first-trimester screening for trisomy 21.
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