Chromosomal Abnormalities and Embryonic Phenotype
Pregnancy loss during the embryonic period of development is a common event. Among the estimated 15 to 20% of clinically recognized pregnancies that are lost, the majority take place when the conceptus is undergoing embryonic development. The abnormal morphology of aborted embryos has been noted by earlier authors (Mall, 1908; Hertig et al., 1936). It has since been recognized that the incidence of cytogenetic abnormalities among such embryonic spontaneous abortions is over 50% (Boué et al., 1975; Jacobs and Hassold, 1987), with chromosomal trisomy, monosomy, and polyploidy being the most common. Nearly all these chromosomal defects are “de novo,” arising either during parental gametogenesis or fertilization/ cleavage. Trisomies and monosomies are caused by meiotic chromosomal nondisjunction; triploidy usually results from double fertilization of an ova by two sperms and tetraploidy from abnormal cleavage. Many studies have been dedicated to answering the question whether an abortion with an identified chromosomal defect—specifically, chromosomal trisomy—predisposes the parents to the higher risk of having a liveborn infant with chromosomal trisomy. When allowance was made for maternal age, no association between spontaneous abortion with aneuploidy and an increased risk of a future liveborn infant with a chromosomal defect could be demonstrated (Warburton et al., 1987).
KeywordsSpontaneous Abortion Neural Tube Defect Recurrent Spontaneous Abortion Abnormal Embryo Chromosomal Defect
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- Fantel AG, Shepard TH, Vadheim-Rok C, Stephens TD, Coleman C Embryonic and fetal phenotypes. Prevalence and other associated factors in a large study of spontaneous abortion, in Potter IH, Hook EB (eds): Embryonic and Fetal Death. New York, Academic Press, 1980, pp 261–287.Google Scholar
- ISCN: An international system for human cytogenetic nomenclature. Report of the standing committee on Human Cytogenic Nomenclature. Cytogenet Cell Genet, Basel, Karger, 1985.Google Scholar
- Jacobs PA, Hassold TJ: Chromosomal abnormalities: Origin and etiology in abortions and live births, in Vogel F, Sperling K (eds): Human Genetics. Springer-Verlag, 1987, pp 233–244.Google Scholar
- Kalousek DK: Anatomic and chromosomal anomalies in specimens of early spontaneous abortion: Seven year experience. Birth Defects. OAS 23:153–168, 1987. New York, Alan R. Liss.Google Scholar
- Warburton D, Stein Z, Kline J, Susser M: Chromosome abnormalities in spontaneous abortion, in Porter IH, Hook EB (eds): Human Embryonic and Fetal Death. New York, Academic Press, 1980, pp 261–288.Google Scholar