Test Details: FISH helps in aneuploidy detection and structural aberration for chromosomes 13, 18, 21, X and Y which account for greater than 90% of chromosomal aberrations. Autosomal monosomies are usually not compatible with life. Autosomal trisomy of chromosomes 13 and 21 are most common trisomy detected in live-births. Trisomy 21 is associated with Down Syndrome and is the single most common known cause of mental retardation. Trisomy 13 is associated with Patau Syndrome. Trisomy 18 is associated with Edward Syndrome. Sex chromosomal aneuploidies including Turner Syndrome (45,X), Klinefelter Syndrome (47,XXY) can also be detected. Structural chromosome rearrangements arise due to chromosome break with subsequent reunion of the wrong segments of the chromosomes. Unbalanced translocation may lead to significant clinical consequences in the form of dysmorphic features and mental abnormality in the child. Balanced translocation may have no phenotypic abnormalities with normal mental and physical fitness in the child. Multiple generations of a family may have members with balanced structural rearrangements without detection and manifest in the form of infertility, recurrent pregnancy loss or abnormal progeny. Genetic counselling to couples is essential to explain the recurrence risk and for planning subsequent pregnancies.