title: Ultrasound findings and multiple marker screening in trisomy 18.
abstract: OBJECTIVE
  To compare detection of trisomy 18 in the second trimester by ultrasound and multiple-marker testing.
  
  
  METHODS
  A computerized genetics database was used to identify fetuses of 14-22 weeks' gestation who had comprehensive ultrasound examinations, multiple-marker screening tests (alpha-fetoprotein [AFP]), hCG, unconjugated estriol [E3], and trisomy 18 karyotype. A positive trisomy 18 screen was defined as AFP up to 0.75 multiples of the median (MoM), hCG up to 0.55 MoM, and unconjugated E3 up to 0.60 MoM. A risk of at least 1:190 defined a positive Down syndrome screen. Ultrasound abnormalities were diagnosed prospectively and were confirmed later by retrospective review of sonographic images.
  
  
  RESULTS
  From 1988-1997, 30 trisomy 18 fetuses who had comprehensive ultrasounds and multiple-marker testing were identified. Twenty-one (70%) had abnormalities detected by ultrasound, of which the most common isolated finding was choroid plexus cyst. Eleven fetuses (37%) had positive trisomy 18 screens, and two had positive Down syndrome screens, for a total of 13 of 30 (43%) fetuses with positive multiple-marker screening tests.
  
  
  CONCLUSIONS
  We found that ultrasound was more likely to be abnormal than multiple-marker screening tests in fetuses with trisomy 18 (70%) (95% confidence interval [CI] 54, 86 versus 43% CI 25, 61). However, combining the two testing methods yielded the highest detection rate (80% [CI 66%, 94%]).
authors.affiliation: Department of Obstetrics and Gynecology, The University of Alabama at Birmingham, 35233-7333, USA. cynthiab@uab.edu
authors.forename: C G
authors.initials: CG
authors.lastname: Brumfield
authors.forename: K D
authors.initials: KD
authors.lastname: Wenstrom
authors.forename: J
authors.initials: J
authors.lastname: Owen
authors.forename: R O
authors.initials: RO
authors.lastname: Davis
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000032:analysis; D006063:Chorionic Gonadotropin / Q000032:analysis; D002887:Chromosomes, Human, Pair 18; D004958:Estradiol / Q000032:analysis; D005260:Female; D006801:Humans; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D014314:Trisomy; D016216:Ultrasonography, Prenatal; D000509:alpha-Fetoproteins / Q000032:analysis
chemical_list: D015415:Biomarkers; D006063:Chorionic Gonadotropin; D000509:alpha-Fetoproteins; D004958:Estradiol