Prenatal diagnosis of trisomy 9

We present a foetus affected by trisomy 9, a rare chromosomal disorder, which was diagnosed in a low-risk patient during the first trimester of pregnancy. The finding of multiple structural foetal anomalies at the first trimester screening prompted chorionic villus sampling. Evaluation of the quantitative fluorescent polymerase chain reaction was normal, but the final karyotype result revealed a diagnosis of trisomy 9. First trimester screening for detection of foetal anomalies is highly effective. Although rapid molecular methods are available for prenatal diagnosis of common autosomal and sex chromosome aneuploidies, it is essential to obtain a full karyotype in order to exclude the less commonly encountered chromosomal abnormalities.