Search

Second trimester maternal serum biochemical markers, introduced between 1990 and 1995, were supplemented with new ultrasound methods at 14-16 weeks and first trimester biochemical markers between 1995 and 2000. This study evaluated the effectiveness of a Down syndrome (DS) prevention program among the Israeli Jewish population between 1990 and 2000. We collected data on the total number of prenatal tests performed on Israeli Jewish women, DS cases detected prenatally and DS livebirths in Israel during these years. We also studied the use of the newer screening tests in 1990, 1992, and 2000. Between 1990 and 1995, use of chromosomal studies for DS in this population increased from 11.3% to 21.6% and the percentage of cases detected prenatally from 53% to 70%. However, between 1996 and 2000, even with the new screening methods, the utilization rate remained similar (20.7% and 19.8%, respectively) and the percentage detected prenatally decreased to 61% in 2000. The total cost per case detected increased from $47,971 US dollars in 1990 to $75,229 US dollars in 1992, and to $190,171 US dollars in 2000. Between 1990 and 1995, improvement in the percentage of cases detected prenatally was associated with a significant increase in the amniocentesis rate-both are attributed to the introduction of second trimester maternal serum biochemical marker tests. Unexpectedly, the introduction between 1995 and 2000 of new genetic methods to assess the DS risk did not improve the percentage detected or reduce the amniocentesis rate, and was accompanied by an increased cost per case detected.

The clinical significance of mosaicism trisomy 20 detected prenatally following amniocentesis remains uncertain, due to the rarity of liveborn cases with inconsistent clinical findings, the short postnatal follow-up, and failure in evaluating other fetal tissues for the presence of the trisomy. We report on a 15 month-old 46,XX chromosome constitution in white blood cells, while skin fibroblasts demonstrated trisomy 20 mosaicism (54%) by fluorescence in situ hybridization (FISH) analysis. Clinical examination of the baby showed only minor phenotypic signs (bilateral epicanthal folds, delayed closure of fontanel with no other gross anomalies), but demonstrated a considerable developmental delay in gross and fine motor skills along with hypotonicity. This is the second oldest described liveborn with trisomy 20 mosaicism confirmed in skin fibroblasts. This cytogenetic aberration along with her developmental delay suggests that the two findings are related and that aberration affects various fetal tissues and is not confined to extra-embryonic tissue as suggested previously. Yet, an undiagnosed condition may be the cause of the child's developmental delay. Based on this case and following a review of the literature we suggest that when mosaic trisomy 20 is identified in amniocytes, further evaluation is required. Cord blood should be analyzed preferably by FISH. During counseling the parents should be advised of an additional risk, such as developmental delay, even when fetal cord karyotype and detailed ultrasonic scan are normal.

We describe three unrelated cases of Wiedemann-Beckwith syndrome (WBS). Two of them were diagnosed postnatally while the third was detected during pregnancy that resulted in elective termination. Amniotic karyotypes were normal in all. PCR amplification of polymorphic loci mapping to 11p15.5 region documented partial trisomy of 11p15.5 due to paternal translocation in one, and segmental and mosaic segmental unipaternal disomy (UPD) in the second and third cases, respectively. Based on findings documented in these cases and the literature, we tabulated the anomalies that might be detected prenatally by ultrasound and that may suggest the syndrome. Constant findings included fetal overgrowth, polyhydramios, enlarged placenta, and specifically a distended abdomen. As most described signs developed after 22 weeks of gestation, a careful follow-up should be carried on until late stages of pregnancy. An amniotic karyotype might not detect subtle chromosomal rearrangements. We therefore recommend utilizing PCR of polymorphic loci on 11p15.5, in addition to conventional cytogenetic analysis of the fetus and both parents to detect possible maternal deletions or inversions, paternal duplications, and UPD that may account for the largest subset of sporadic WBS reaching 25% of cases. An early diagnosis of WBS is important for counseling the parents concerning potential risk for developing embryonic tumors, selection of the mode of delivery due to potential adrenal cysts that might bleed during labor, and prevention of neonatal hypoglycemia.