Prenatal karyotype results from 2169 invasive tests.

Objectives: Foetal karyotyping is a basic tool used to diagnose the most common genetic syndromes. Although new molecular methods such as FISH, MLPA or QF-PCR allow rapid prenatal testing, they are of limited value when diagnosing less frequent chromosomal abnormalities. Chromosomal microarray analysis offers higher test resolution than traditional karyotyping and has been recommended as first-line genetic testing in prenatal diagnosis. The aim of the study was to confirm whether foetal karyotyping remains a valid approach to prenatal diagnosis by analysing its performance in a large population of pregnant women with a high risk of chromosomal aberration.

Material and methods: An analysis was performed of 2169 foetal karyotypes from two referral university centres for prenatal diagnostics in Lodz, Poland.

Results: Amniocentesis and foetal karyotyping were performed when screening methods had indicated a high risk of chromosomal aberration, or when prenatal ultrasound had proved foetal abnormality. The study group included 205 (9.4%) abnormal foetal karyotypes. Rare aberrations were observed in 34 cases (e.g., translocations, inversions, deletions and duplication). A marker chromosome was present in five cases.

Conclusions: One third of the chromosomal abnormalities observed in the prenatal tests were rarer aberrations (i.e., not trisomy 21, 18 or 13). As many of these could not be detected by the new molecular methods, foetal karyotyping remains an important component of prenatal diagnosis.