Evaluation of the proportion of Genetic Disorders detected at prenatal testing in a Tertiary fetal medicine referral centre

Abstract

OBJECTIVE: Prenatal suspicion of fetal chromosomal aneuploidies is the most common indication for invasive prenatal testing. Amniocentesis followed by genetic testing for chromosomal aneuploidies is the diagnostic technique for prenatal detection of chromosomal disorders. Prenatal detection of these disorders would enable timely medical or surgical treatment of a condition before or after birth. It further “prepare” the family psychologically, socially, financially, andmedically of a baby with a health problem or disability or for the likelihood of a still birth. The objective of this study was to evaluate the proportion of genetic disorders detected at prenatal testing procedures at a Tertiary Fetal Medicine referral centre. METHODS: A retrospective study was carried out from 2016 October to 2017 April in all invasive procedures done in the Fetal Medicine Unit, Ninewells Care Mother & Baby hospital, Colombo, Sri Lanka. Prenatal samples were analyzed by Fluorescent in situ hybridization for the common chromosomal aneuploidies including chromosome number 13, 18, 21, X andY and by karyotype. Patient information and details of invasive procedures were obtained from the Fetal Medicine Unit database. RESULTS: A total of 57 prenatal examinations was performe during the study period of which 55 were amniocentesis and 02 were cordocentesis procedures. The mean maternal age at which the procedure was performed was 33 years(SD=6.3). The commonest indication for the prenatal testing was increased nuchal translucency (NT) thickness (27) detected at the NT scan. The other common indications for prenatal detection were atrioventricular septal defect (5), omphalocoele (4), nonimmunehydrops (3) and Diaphragmatic hernia (2) detected at the second trimester scan. There were 3 who had elevated double test and1 with increased Non Invasive Prenatal test result which directed them for prenatal testing. Chromosomal abnormalities were detected in 13 fetuses of which majority were Trisomy 18 (5). Trisomy 21 and Trisomy 13 syndromes were detected in 4 and 3 fetuses respectively. Of the 27 fetuses who had elevated NT thickness, 4 fetuses were Trisomy 21. Fetuses who had structural abnormalities 4 had Trisomy 18 syndrome. There was one which had Trisomy 21 mosaic syndrome and one with Turner mosaic syndrome. CONCLUSION: Testing for diseases or conditions in a fetus/embryo by an invasive method before it is born would enable the doctors to improve the outcome of the developing fetus/embryo hence prepare the family for an anticipated problem.