Balanced and unbalanced reciprocal translocation: An overview of a 30-year experience in a single tertiary medical center in Taiwan

BackgroundReciprocal translocation is the most common type of translocation; however, there are only a few studies that address the indications for reciprocal translocation in amniocentesis. Here we share our data, based on 30 years' experience in a single tertiary center, to investigate the rates and indications for amniocentesis in cases of reciprocal translocations.MethodsA retrospective review of 16,749 pregnant women, who underwent midtrimester amniocentesis between January 1981 and December 2010, was conducted. Seventy-four cases of reciprocal translocation were identified.ResultsThe percentage of reciprocal translocations in all amniocentesis cases was 0.44% (74/16,749); of these 74 cases, 56 were balanced and 18 unbalanced. De novo abnormality occurred in 23 cases, which constituted 31.1% of all reciprocal translocations. The three major indications for amniocentesis with a diagnosis of reciprocal translocation included advanced maternal age (AMA, 52.7%), a parent with an abnormal karyotype (17.6%), and abnormal biochemical markers in the maternal serum (12.2%). For individual types of reciprocal translocations (balanced and unbalanced), except for the presence of abnormal biochemical markers in maternal serum, both AMA and a parent with an abnormal karyotype were primary indications for amniocentesis. However, the highest percentage of reciprocal translocations in all amniocentesis cases was found in cases involving a parent with an abnormal karyotype (5.16%, 13/252).ConclusionPatients with a parent who carries an abnormal karyotype should be encouraged to undergo amniocentesis in prenatal consultation, since the risk of a diagnosis of reciprocal translocation can be particularly high.