title: Ultrasound and fetal diagnosis.
abstract: OBJECTIVE
  The purpose of this review is to highlight publications from the last year that have advanced the use of ultrasound in obstetrics.
  
  
  RESULTS
  Anatomic examination of the fetus in the first trimester has been emphasized because it allows for early diagnosis of many conditions. The prevalence of absent nasal bone, a marker for trisomy 21, in euploid fetuses depends on ethnicity. Nasal bone hypoplasia is another marker for Down syndrome. Studies on genetic screening in the first trimester have involved various serum analytes, adjustments in timing and calculations, use in multiple gestations, and the association of extreme measurements with adverse outcomes. A first-trimester integrated screening approach, which incorporates nuchal translucency, nasal bone, crown-rump length, pregnancy-associated plasma protein-A, and free beta-human chorionic gonadotropin, has the potential to maximize detection rates of Down syndrome and trisomy 18 and minimizes the screen-positive rate. The value of combining first and second-trimester results in sequential, contingent, or integrated screening protocols has been assessed. Isolated mild ventriculomegaly (10-12 mm) may prove to be a normal variant, and the role of 'soft' ultrasound markers in genetic counseling continues to be debated. Anomaly or high-risk status detection in the second trimester has been enhanced by the use of Doppler, 3D/4D ultrasound, and magnetic resonance imaging.
  
  
  CONCLUSIONS
  Imaging techniques have been critical in the development of screening methods for Down syndrome or trisomy 18 and for euploid fetuses at high risk for adverse outcomes.
authors.affiliation: Department of Obstetrics and Gynecology, University of California, Irvine, California, USA. karen_filkins@pediatrix.com
authors.forename: Karen
authors.initials: K
authors.lastname: Filkins
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Koos
mesh_terms: D000782:Aneuploidy; D002869:Chromosome Aberrations / Q000196:embryology; D005260:Female; D005315:Fetal Diseases / Q000175:diagnosis* / Q000235:genetics; D005333:Fetus / Q000098:blood supply; D006801:Humans; D009295:Nasal Bone / Q000000981:diagnostic imaging; D048208:Nuchal Translucency Measurement; D011247:Pregnancy; D011248:Pregnancy Complications / Q000175:diagnosis*; D011256:Pregnancy Outcome; D011264:Pregnancy Trimesters; D013997:Time Factors; D016216:Ultrasonography, Prenatal / Q000379:methods*; D014599:Uterus / Q000098:blood supply / Q000000981:diagnostic imaging