Rapid diagnosis of triploidy of maternal origin using fluorescent PCR and DNA fragment analysis in the third trimester of pregnancy

OBJECTIVES: Triploidy is a common cause of spontaneous abortion in the very early stages of pregnancy. It is very rare for a prenatal diagnostic center to discover triploidy in the third trimester of pregnancy. A pregnant woman in the third trimester was referred to our genetic counselling clinic because of abnormal ultrasound findings. We planned to test for the most common chromosomal abnormalities. METHODS: We performed ultrasound examination, chorionic villus sampling, karyotyping and fluorescent-polymerase chain reaction (F-PCR) and fragment analysis. RESULTS: We diagnosed a 69,XXX karyotype fetus in the 31st week of gestation, based on a short tandem repeat (STR) pattern typical for triploidy, which was confirmed by karyotyping. The comparison of the fetal and parental STR patterns showed maternal origin of the extra haploid chromosome set. CONCLUSIONS: STR analysis of fluorescent-PCR and DNA fragment analysis is a rapid and reliable alternative to karyotyping for detection of certain aneuploidies. The method is also suitable for the determination of the origin of the extra chromosome set.