Test Details: Karyotyping helps to detect chromosomal aberrations which can result from either a variation in chromosome number or from structural rearrangement. Numerical aberrations or aneuploidies may be in the form of loss or gain of chromosomes. Autosomal monosomies are usually not compatible with life. Autosomal trisomy of chromosome 13, 18 and 21 are most common trisomy detected in live-births. Trisomy 21 is associated with Down Syndrome and is the single most common cause of mental retardation. Trisomy 18 is associated with Edward Syndrome. Trisomy 13 is associated with Patau Syndrome. The common sex chromosomal aneuploidies include Turner Syndrome (45,X) and Klinefelter Syndrome (47,XXY). Karyotyping of fetal cord blood sample is indicated when the patient presents late in gestation and is case of advanced maternal age, or has history of chromosomal aberrations in previous pregnancy, high risk of maternal serum screening tests, abnormal USG findings and/or either/both parents are carriers of balanced translocations.