INTEGRATION OF GENETICS AND ULTRASONOGRAPHY IN PRENATAL-DIAGNOSIS - JUST LOOKING IS NOT ENOUGH

OBJECTIVE: There has been a gradual shift of the focus of prenatal dia gnosis from genetics to ultrasonography. We assessed our primary genet ics approach to determine what would be missed without the genetics co mponent. STUDY DESIGN: We evaluated referral indications for patients with normal and abnormal prenatal findings from Jan. 1, 1990, to March 31, 1995, and categorized them according to type of fetal anomalies a nd genetic abnormalities found. Discordance among initial indication, identified risk factors, and observed abnormalities was assessed. RESU LTS: The proportion of patients referred for very-high-risk indication s increased over time; 13.5% of all patients (1992 of 14,725) had abno rmalities. Abnormal outcomes were categorized as 26% chromosomal, 58% ultrasonographic dysmorphologic features, 11% biochemical or deoxyribo nucleic acid disorders, 5% infectious, and 11% other. Of the cases of ultrasonographic dysmorphism (exclusive of the aneuploidies), 3.5% wer e ultimately determined to be syndromic and 2.5% to be discrepant, tha t is, having a different abnormality than the referred diagnosis. Incl uding the whole spectrum of disorders seen, half of the abnormalities would not be detectable with even high-quality ultrasonography. CONCLU SION: A large number of abnormal findings were not consistent with ini tial indication for referral. Correct diagnosis depended on increased acuity provided by genetic pedigree analysis and recognition of syndro mes. Diligence in the search for associated anomalies, aneuploidy, ped igree analysis, and syndromic abnormalities remain critical components in the differential diagnosis. The elucidation of unexpected findings suggests the advantages of early counseling and a genetics-based appr oach combined with tertiary ultrasonography rather than primary ultras onography with counseling only when anomalies are detected.