Fetal Chromosomal Polymorphisms

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Why is it important?

Chromosomal polymorphism or normal variant, are the heritable variations at specific chromosomal regions, called heterochromatin, without phenotypic effect. The clinical importance of polymorphisms is not yet fully known. But some authors reported that there was an association between chromosomal polymorphism and embryonic development disorders, male infertility, recurrent abortion, mental retardation. In this study we aimed to determine fetal polymorphism rate in in pregnant women who had been implemented for invasive prenatal test in our region. Secondly, we investigated whether there is a relationship between fetal polymorphism and first/second trimester prenatal screening test parameters. To our knowledge, we observed lower Pregnancy-associated plasma protein-A (PAPP-A) values in women having fetuses with polymorphisms on chromosome 9, for the first time. It is known that PAPP-A is encoded by PAPP-A gene which is localized on 9q33.1 chromosomal region. In this study we found that fetal polymorphism on chromosome 9 may affect PAPP-A glycoprotein expression in the maternal circulation. We concluded that lower PAPP-A values in these women may affect the placental function and first trimester screening test results (higher risk for trisomies).