THE ROLE OF MIDTRIMESTER TARGETED FETAL ORGAN SCREENING COMBINED WITHTHE TRIPLE TEST AND MATERNAL AGE IN THE DIAGNOSIS OF TRISOMY-21 - A RETROSPECTIVE STUDY

OBJECTIVE: Our purpose was to evaluate the role of fetal ultrasonograp hy in prenatal detection of trisomy 21. STUDY DESIGN: A retrospective study was performed on all cases of trisomy 21 diagnosed prenatally or postnatally between January 1990 and December 1993 in the Jerusalem m etropolitan area. Our program of prenatal detection of trisomy 21 is a three-tiered, chronologically progressive screening that includes mat ernal age, biochemical serum markers, and targeted fetal organ survey. Sixty-seven thousand ninety-two babies were born during the study per iod; 17,084 maternal biochemistry analyses (triple test) were performe d; and 6315 fetuses were karyotyped. RESULTS: One hundred eight cases of trisomy 21 were diagnosed prenatally and postnatally. The overall r ate of detection of trisomy 21 was 92.2% when our recommendations were followed. Among those cases diagnosed prenatally, 66.6% of trisomy 21 cases had been referred for fetal karyotyping because of maternal age greater than or equal to 35 years, 18.5% because of abnormal triple t est results, and 11.1% because of fetal ultrasonographic findings asso ciated with trisomy 21. Among women <35 years old, 80% of trisomy 21 c ases were detected prenatally. Of these, 50% had been referred for kar yotyping because of triple test results and 30% because of abnormal ul trasonographic findings. CONCLUSION: Midtrimester ultrasonographic tar geted fetal organ screening plays a critical role in prenatal diagnosi s of trisomy 21 among women under the age of 35 years.