Indications of invasive genetic study in a selected population: August 2005 to December 2007 Indicaciones de estudio genético invasivo en una población seleccionada: Agosto de 2005 a diciembre de 2007

Abstract

Background: the greater use of prenatal ultrasound and invasive diagnostic procedures has made it possible to improve the identification of fetal malformations at birth. The dilemma involves a risk related to the procedure, so physicians continue to grapple with how to identify high-risk patients so as not to subject those at low risk to unnecessary diagnostic procedures. In the present study we have set out to describe the different indications for the invasive genetic diagnosis of chromosomal alterations in a selected population of Bogotá D.C. PATIENTS AND METHODS: A cross-sectional descriptive study was conducted between August 1, 2005 and December 31, 2007. The medical records of pregnant women referred with an indication of invasive genetic study due to chromosomal abnormalities were reviewed. Results: 374 pregnancies were analyzed, of which 98.9% (n = 370) were simple and 1.1% (n = 4) corresponded to twins, for a total of 378 analyzes of the fetal karyotype. The average maternal age was 35 years and the average gestational age was 17.4 weeks. 366 amniocentesis (96.8%) and 12 chorionic villus biopsies (3.2%) were performed. The most requested cytogenetic study was the 64.8% karyotype (n = 245) and 33.6% (n = 127) of the cases were analyzed by FISH and karyotype. Among the indications for requesting an invasive genetic study, maternal age stands out with 35.7% (n = 135), followed by minor sonographic malformations 14.8% (n = 56), second trimester screening 9.3% (n = 35). ), increased nuchal sonography 6.9% (n = 26) and major sonographic malformations 6.3% (n = 24). 54 altered cytogenetic studies (14.3%) were reported; Of these, 36 corresponded to aneuploidies (66.67%) and eighteen to structural variations (33.33%). When maternal age was the only indication of an invasive procedure, only 6.66% of altered karyotypes were detected, while in the group where the indication was due to minor malformations, major malformations and nuchal sonolysis, the diagnosis of aneuploidy was made in 25%, 29% and 26% respectively. Conclusions: the decision to offer invasive tests should not be based only on maternal age. The differences between screening and diagnostic tests should be discussed with all patients. Thus, the maternal age of 35 years should no longer be considered as an independent cut-off point to determine who is offered screening or invasive tests. Although precise non-invasive prenatal diagnosis has not been achieved, technological advances continue to focus on improving individual risk assessment, so that the number of invasive diagnostic procedures and gestational losses associated with the procedure can be minimized. Abbreviations: ECO, ultrasound, ultrasound; RN, newborn (s).