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The use of second-trimester genetic sonogram in guiding clinical management of patients at increased risk for fetal trisomy 21.

AbstractOBJECTIVE:
To test the efficacy of ultrasound in detecting fetuses with trisomy 21.
METHODS:
From November 1, 1992, to December 31, 1995, a second-trimester genetic sonogram was offered to all women with singleton fetuses at increased risk (at least 1:274) for trisomy 21, who had either declined genetic amniocentesis or chose to have a sonogram before deciding whether to undergo an amniocentesis. In addition to standard fetal biometry, the following ultrasound markers for aneuploidy were evaluated: structural anomalies (including face, hands, and cardiac [four-chamber view and outflow tracts]), short femur, short humerus, pyelectasis, nuchal fold thickening, echogenic bowel, choroid plexus cysts, hypoplastic middle phalanx of the fifth digit, wide space between the first and second toes, and two-vessel umbilical cord. Outcome information included the results of genetic amniocentesis, if performed, or the results of postnatal pediatric assessment and follow-up.
RESULTS:
Five hundred seventy-three patients had a genetic sonogram between 15 and 23 weeks' gestation: 378 patients had advanced maternal age (at least 35 years), 141 had abnormal serum biochemistry, and 54 had both. The majority (495, or 86.3%) had a normal genetic sonogram (absence of abnormal ultrasound markers); 51 (9%) had one marker present, and 27 (4.7%) had two or more markers present. Outcome was obtained on 422 patients (the remaining were ongoing pregnancies or were lost to follow-up). Twelve of 14 fetuses with trisomy 21, one fetus with trisomy 13, and one fetus with triploidy had two or more abnormal ultrasound markers present; one fetus with trisomy 21 had one abnormal marker and one had a completely normal ultrasound. When one or more abnormal ultrasound markers were present, the sensitivity, specificity, and positive and negative predictive values for trisomy 21 were 92.8%, 86.7%, 19.4%, and 99.7%, respectively. When two or more abnormal ultrasound markers were present, the corresponding values were 85.7%, 96.8%, 48%, and 99.5%. In the study population, the amniocentesis rate was 12.7% overall and 17.3% in cases with known outcome.
CONCLUSION:
Second-trimester genetic sonogram may be a reasonable alternative for patients at increased risk for fetal trisomy 21 who wish to avoid amniocentesis. In experienced hands, this approach may result in a high detection rate of trisomy 21 (93%), with an amniocentesis rate of less than 20%.
AuthorsA M Vintzileos, W A Campbell, J F Rodis, E R Guzman, J C Smulian, R A Knuppel
JournalObstetrics and gynecology (Obstet Gynecol) Vol. 87 Issue 6 Pg. 948-52 (Jun 1996) ISSN: 0029-7844 [Print] United States
PMID8649704 (Publication Type: Journal Article)
Topics
  • Adult
  • Amniocentesis
  • Congenital Abnormalities (diagnostic imaging)
  • Down Syndrome (diagnostic imaging)
  • Female
  • Fetal Diseases (diagnostic imaging)
  • Humans
  • Maternal Age
  • Predictive Value of Tests
  • Pregnancy
  • Pregnancy Trimester, Second
  • Pregnancy, High-Risk
  • Prospective Studies
  • Risk Factors
  • Sensitivity and Specificity
  • Ultrasonography, Prenatal

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