Balanced reciprocal translocation at amniocentesis: cytogenetic detection and implications for genetic counseling.

ABSTRACT

Balanced translocation is a common structural chromosomal rearrangement in humans. Carriers can be phenotypically normal but have an increased risk of pregnancy loss, fetal death, and the transmission of chromosomal abnormalities to their offspring. Existing prenatal screening technologies and diagnostic procedures fail to detect balanced translocation, so genetic counseling for carriers remains a challenge. Here, we report the characteristics of chromosomal reciprocal translocation in 3807 amniocentesis cases. Of the 16 detected cases of fetal reciprocal translocation, 8 cases (50%) showed positive biochemical marker screening; 3 cases (18.75%) were the parental carriers of a chromosomal abnormality; 2 (12.5%) were of advanced maternal age, 2 (12.5%) had a previous history of children with genetic disorders, and 1 case (6.25%) was associated with positive soft markers in obstetric ultrasound. Chromosomes 5 and 19 were the most commonly involved chromosomes in balanced translocations. Of the 13 cases with fetal balanced translocations, 8 (61.5%) were inherited from a paternal chromosome, 3 (23.1%) from a maternal chromosome, and 2 (15.4%) cases were de novo. The incidence of balanced translocation at amniocentesis was 0.42%. Male carriers of reciprocal chromosome translocation appear to have a higher chance of becoming a parent of a child born by normal childbirth than female carriers.