Chromosomal abnormalities includes 1) abnormalities in number of chromosomes which are known as aneuploidies and 2) structural defects like translocations and deletions. In this we will discuss about Aneuploidies The incidence of Aneuploidy is around one in 200 live births. Aneuploidy increases with advancing maternal age. Fetal aneuploidy has been associated with significant pregnancy complications such as growth restriction, congenital malformations and perinatal deaths. Several Major developments are happened in prenatal screening of Aneuploidy especially the introduction of first trimester screen with Nuchal thickness and fetal cell free DNA in maternal plasma and identification of ultrasound markers and biochemical screening in second trimester. In this chapter we will discuss about what are trisomies, why “Down syndrome” is important to detect prenatally, history of “Down syndrome”, advances in screening methods biochemical as well as sonographic markers in first and second trimester and the criteria to get those markers. What are the features of trisomy 21, trisomy18 and trisomy13.
Part of the book: Down Syndrome and Other Chromosome Abnormalities