Nuchal translucency and other first-trimester sonographic markers of chromosomal abnormalities.
There is extensive evidence that effective screening for major chromosomal abnormalities can be provided in the first trimester of pregnancy. Prospective studies in a total of 200,868 pregnancies, including 871 fetuses with trisomy 21, have demonstrated that increased nuchal translucency can identify 76.8% of fetuses with trisomy 21, which represents a false-positive rate of 4.2%. When fetal nuchal translucency was combined with maternal serum free-beta-human chorionic gonadotropin and pregnancy-associated plasma protein-A in prospective studies in a total of 44,613 pregnancies, including 215 fetuses with trisomy 21, the detection rate was 87.0% for a false-positive rate of 5.0%. Studies from specialist centers with 15,822 pregnancies, which included 397 fetuses with trisomy 21, have demonstrated that the absence of the nasal bone can identify 69.0% of trisomy 21 fetuses, which represents a false-positive rate of 1.4%. It has been estimated that first-trimester screening by a combination of sonography and maternal serum testing can identify 97% of trisomy 21 fetuses, which represents a false-positive rate of 5%, or that the detection rate can be 91%, which represents a false-positive rate of 0.5%. In addition to increased nuchal translucency, important sonographic markers for chromosomal abnormalities, include fetal growth restriction, tachycardia, abnormal flow in the ductus venosus, megacystis, exomphalos and single umbilical artery. Most pregnant women prefer screening in the first, rather than in the second, trimester. As with all aspects of good clinical practice, those care givers who perform first-trimester screening should be trained appropriately, and their results should be subjected to external quality assurance.
Harris Birthright Research Centre for Fetal Medicine, King's College, London University, Denmark Hill, London SE5 8RX. Kypros@fetalmedicine.com
Kypros H
KH
Nicolaides
D000328:Adult; D001290:Attitude; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000097:blood; D002869:Chromosome Aberrations; D002882:Chromosomes, Human, Pair 13; D002887:Chromosomes, Human, Pair 18; D018568:Crown-Rump Length; D004314:Down Syndrome / Q000175:diagnosis; D005260:Female; D006801:Humans; D008403:Mass Screening / Q000523:psychology; D008423:Maternal Age; D009295:Nasal Bone / Q000002:abnormalities / Q000000981:diagnostic imaging; D009333:Neck / Q000000981:diagnostic imaging* / Q000196:embryology; D011237:Predictive Value of Tests; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011262:Pregnancy Trimester, Second; D011266:Pregnancy-Associated Plasma Protein-A / Q000032:analysis; D014314:Trisomy / Q000175:diagnosis*; D016216:Ultrasonography, Prenatal
D018997:Chorionic Gonadotropin, beta Subunit, Human; D011266:Pregnancy-Associated Plasma Protein-A