Impact of prenatal diganosis on the prevalence of live births with Down sysndrome in the eastern half of Switzerland 1980-1996

Objectives and methods: To investigate the impact of prenatal diagnosis on trisomy 21 live births, we collected all prenatal and postnatal trisomy 21 cases (n = 1096) in the eastern half of Switzerland for the years 1980-1996. Results: Despite increasing prenatal detection rates of trisomy 21 foetuses (an increase of 169% in the last 5 versus the first 5 years of the study period) and subsequent termination of pregnancies, the number of liveborn Down syndrome children remained constant. The reason is a shift towards a higher mean maternal age from 28 to 30 years between 1980 and 1996. If mean maternal age at delivery was considered, the observed increase of trisomy 21 conceptions matched well with the calculated figures. Conclusion: If the tendency to have pregnancies at a more advanced age continues and if the use of prenatal diagnosis does not increase, an increase in incidence of Down syndrome liveborns may be expected in the first decades of the 21st century

Complex rearranged small supernumerary marker chromosomes (sSMC), three new cases; evidence for an underestimated entity?

<p>Abstract</p> <p>Background</p> <p>Small supernumerary marker chromosomes (sSMC) are present ~2.6 × 10⁶human worldwide. sSMC are a heterogeneous group of derivative chromosomes concerning their clinical consequences as well as their chromosomal origin and shape. Besides the sSMC present in Emanuel syndrome, i.e. der(22)t(11;22)(q23;q11), only few so-called complex sSMC are reported.</p> <p>Results</p> <p>Here we report three new cases of unique complex sSMC. One was a <it>de novo </it>case with a dic(13 or 21;22) and two were maternally derived: a der(18)t(8;18) and a der(13 or 21)t(13 or 21;18). Thus, in summary, now 22 cases of unique complex sSMC are available in the literature. However, this special kind of sSMC might be under-diagnosed among sSMC-carriers.</p> <p>Conclusion</p> <p>More comprehensive characterization of sSMC and approaches like reverse fluorescence in situ hybridization (FISH) or array based comparative genomic hybridization (array-CGH) might identify them to be more frequent than only ~0.9% among all sSMC.</p

Werner Schmid 1930-2002

In Memoria

Impact of prenatal diagnosis on the prevalence of live births with Down syndrome in the eastern half of Switzerland 1980-1996

OBJECTIVES AND METHODS To investigate the impact of prenatal diagnosis on trisomy 21 live births, we collected all prenatal and postnatal trisomy 21 cases (n = 1096) in the eastern half of Switzerland for the years 1980-1996. RESULTS Despite increasing prenatal detection rates of trisomy 21 foetuses (an increase of 169% in the last 5 versus the first 5 years of the study period) and subsequent termination of pregnancies, the number of liveborn Down syndrome children remained constant. The reason is a shift towards a higher mean maternal age from 28 to 30 years between 1980 and 1996. If mean maternal age at delivery was considered, the observed increase of trisomy 21 conceptions matched well with the calculated figures. CONCLUSION If the tendency to have pregnancies at a more advanced age continues and if the use of prenatal diagnosis does not increase, an increase in incidence of Down syndrome liveborns may be expected in the first decades of the 21st century

Pre-implantation embryos of Chinese hamster. I. Incidence of karyotype anomalies in 226 control embryos

Karyotypes were determined in 226 pre-implantation embryos (4–8-cell stages) of Chinese hamster. The study was carried out under controlled natural breeding conditions, without superovulation and with the embryos developing in their mothers. A total of 5.3% karyotypically abnormal embryos were found. Over half, 3.1%, were due to ploidy mutations, 5 cases of triploidy and 2 cases of haploidy. Only 0.9% genome mutations were present, consisting of one autosomal trisomy and one autosomal monosomy. Structural aberrations were found in 1.8%, half of these probably due to a balanced maternal aberration and the rest appearing in mosaic condition only. These results are compared with the scarce body of mammalian data from the literature. Compared with the situation in man, the spontaneous aberration rates in the Chinese hamster and other experimental mammals are extremely low. This may be due, in part, to the optimal timing of copulation in respect to estrus and ovulation prevailing in these animals but not in man. The low spontaneous aberration rate in the reported system is a valuable asset for purposes of mutagen testing

Pre-implantation embryos of chinese hamster. II. Incidence and type of karyotype anomalies after treatment of the paternal post-meiotic germ cells with an alkylating mutagen

Ninety-two male Chinese hamsters were treated with a single, sub-lethal dose of the alkylating cytostatic drug Trenimon. After 3--23 days they were mated with untreated females. The great majority of the male germ cells had been exposed to the mutagen while they were in the highly sensitive post-meiotic spermatid stage. The karyotypes of the resulting embryos were studied in the 4--8-cell stage. Out of 221 analysable embryos, 24.4% had aberrant karyotypes. Ploidy and genome mutations were, at 0.9% each, within control limits. Structural aberrations, involving one or several chromosomes, were present in 23.6% of the embryos (control 1.8%). 51% had a single aberrant centric element. The most frequent aberration types were deletions (54%), dicentrics (16%), translocations inversions and complex rearrangements with 22% and rings with 7%. About one-third of the cells, in addition, contained acentric fragments