Sonographic markers of fetal trisomies: second trimester.

Abstract

Objective. Second-trimester sonographic findings of fetal trisomy may include structural abnormalities or sonographic markers of fetal aneuploidy. Unlike structural anomalies, sonographic markers of fetal aneuploidy are insignificant by themselves with regard to outcome, are nonspecific-most frequently seen in normal fetuses, and are often transient. Our objective was to review the secondtrimester sonographic findings of the major trisomic conditions, trisomies 13, 18, and 21. Methods. We reviewed a number of the most commonly accepted markers, including nuchal thickening, hyperechoic bowel, echogenic intracardiac focus, renal pyelectasis, shortened extremities, mild cerebral ventricular dilatation, and choroid plexus cysts. Markers associated with trisomy 21 were emphasized. Results. The sensitivity of sonography for detection of fetal trisomic conditions varies with the type of chromosome abnormality, gestational age at the time of sonography, reasons for referral, criteria for positive sonographic findings, and the quality of the sonography. As an estimate, 1 or more sonographic findings can be identified in approximately 90% of fetuses with trisomy 13, 80% of fetuses with trisomy 18, and 50% to 70% of fetuses with trisomy 21 (Down syndrome). Conclusions. The presence or absence of sonographic markers can substantially modify the risk of fetal Down syndrome and is the basis of the so-called genetic sonogram. Because maternal biochemical and sonographic markers are largely independent, combined risk estimates will result in even higher detection rates than either alone.

Trisomy 18: Fetal ultrasound findings at different gestational ages

“…Invasive diagnostic tests are supported by serum screening tests and by the study of ultrasonographic features [De Vore, 2000]. The sonographic markers can identify approximately 80% of fetuses with trisomy 18 [Bundy et al, 1986;Benacerraf et al, 1988Benacerraf et al, , 1990Nyberg et al, 1993;Seoud et al, 1994;Salihu et al, 1997;Grandjean et al, 1998;Shields et al, 1998;Brumfield et al, 2000;Brun et al, 2000;De Vore, 2000;Feuchtbaum et al, 2000;Nyberg and Souter, 2001;Tongsong et al, 2002;Yeo et al, 2003;Brosteen et al, 2004;Sahinoglu et al, 2004]. In fact the majority of affected fetuses have at least one sonographic abnormality.…”

Screening of trisomy 21 nowadays. Is maternal age so important?

“…A Down-szindrómás magzatok jelentős hányada mutat egy vagy több gyanújelet [9], azonban ezeket a gyanújeleket euploid magzatok is mutathatják. A második trimeszterbeli ultrahangjeleken alapuló szűrés szenzitivitása alacsony (átlagosan 70%), a fals pozitív ráta pedig magas (5-15%) [10]. A major jelek közül a legerősebb második trimeszteri gyanújel az 5 mm-nél vastagabb tarkópárna, hypoplasiás vagy hiányzó orrcsont, szívfejlődési rendellenesség, amely utóbbi legtöbbször kamrai sövényhiány vagy endocardialis párnadefektus.…”

Three-Dimensional Sonographic Features of Nuchal Edema

“…With respect to the definition of nuchal edema, its thickness was measured on an axial view of the skull, and a threshold of 5 mm (or 6 mm) or greater after 15 weeks has been used as a cutoff value for the detection of suspected fetal aneuploidy [13]. More precisely, ^5 mm up to 18 weeks and 6 mm from 18 to 22 weeks are used as cutoff values [14].…”