ROLE OF ULTRASONOGRAPHY IN PREGNANCIES WITH MARKER CHROMOSOME ANEUPLOIDY

The objective of this report was to evaluate the effect of ultrasonogr aphic (US) findings on pregnancy management in patients with marker ch romosome (MC) aneuploidy ascertained through prenatal diagnosis. From 1989 through June 1993, 15,522 prenatal diagnostic procedures were per formed for accepted indications. Charts of patients with MC on amnioce ntesis or chorionic villus sampling (CVS) karyotype were evaluated wit h respect to US anomalies, pregnancy complications, and outcome. Ninet een cases of MC were identified. The prevalence of MC in our study was 0.12%(1:816 procedures). No significant difference between CVS and am niocentesis was found: 5/19 (26%) were CVS specimens, which is compara ble to our CVS (3,259/15,522) case distribution. Three cases with inco mplete records were excluded from the analysis. Four inherited MC case s were identified; 1 case had anencephaly. Of the 12 de novo MC cases 4 (33%) had abnormal US findings, and an additional 4 were found to ha ve cytogenetic evidence for partial trisomy. Seven of these 8 abnormal de novo MC cases were terminated. MC aneuploidy is more common in pre gnancies sampled for usual genetic indications than previously reporte d in pediatric series. High-resolution US may identify a major malform ation not etiologically related to a MC inherited from a normal phenot ypic parent. The association of the novo MC with US anomalies confers a poor prognosis, suggesting the expression of genetic imbalance from the accessory chromatin (partial trisomy). However, when US appears no rmal on initial and follow-up examinations, the chances for a normal-p henotypic newborn are high.