A 13-year cytogenetic study of spontaneous abortion: clinical applications of testing

Chromosome analysis was performed on 1,543 specimens of first trimester miscarriage received between 1982 and 1994. Comparisons with earlier studies show that some findings are absolutely consistent between different years and populations, but some major differences are also found. The results are considered in the light of several recent genetic, environmental and physiological studies. Trisomy 16, and probably trisomy 22, is entirely dependent on maternal age; other trisomies show both maternal age and other environmental or genetic effects. Monosomy X and mosaic aneuploidy arise postzygotically by chromosome loss, a normal control mechanism. Some trisomy, dipaternal triploidy and tetraploidy probably occur because of pre- or postovulatory 'overripeness'; either due to transient or chronic maternal conditions or delayed fertilization. Unbalanced structural abnormalities, most apparently of de novo origin, are markedly increased compared to earlier studies and are possibly due to paternal environmental exposures. It is concluded that when considering histories of abortion, studies of the chromosomes of the aborted products are much more informative and cost-effective than studies of parental bloods. Where available, studies of products should be undertaken for preference, but only by experienced and committed laboratories.