Objective of the study:
At the moment of study design, there was no data available on prevalence of subtelomeric imbalanced rearrangements in fetuses with abnormal phenotype assessed by ultrasound and with normal classical karyotype, consequently this study was initiated to fill in this gap.
Material & Method:
Amniotic fluid samples or chorionic villi from:
137 fetuses with abnormalities in two or more organ systems
96 fetuses with nuchal translucency above 3.5 mm (99th centile),
85 apparently healthy fetuses (control group) were studied by subtelomeric MLPA, using two kits (P036 and P070) in all cases. Confirmation of a rearrangement was obtained by means of fluorescence in situ hybridization (FISH) studies.
In the group of fetuses with abnormalities in two or more organ systems, one subtelomeric deletion (de novo deletion (del1p36).) was detected, yielding the detection rate of cryptic subtelomeric imbalances in these pregnancies of 0.84%. In the control group and in the group of fetuses with NT measurement above 3.5 mm, no abnormalities were found.
The low detection rate of subtelomeric rearrangements in the studied group, together with the low robustness of the method (only one sequence per telomere is studied in one experiment) and necessity to confirm the pathological findings with another method, imply low usefulness of the method in the prenatal setting. In the current era, there are genome-wide methods, like CGH-arrays or SNP-array, which are better-suited for prenatal diagnosis, because of higher yields and lack of necessity of confirmation of the pathological results.