Abstract:

A case of 69, XXX homozygous triploid was reported. This is a 24-year-old, 21-week-pregnant woman with adverse pregnancy and childbirth history. The serum prenatal screening showed the high risk of 18-trisomy syndrome. The four-dimensional color ultrasound suggested some abnormality, and the non-invasive prenatal testing (NIPT) suggested the high risk of sex chromosome aneuploidy. After that, the in-depth genetic testing and analysis by the short tandem repeat (STR) fragment analysis and fetal chromosome karyotype analysis were done with the informed consent. In this case, the fetal chromosome karyotype was 69, XXX, and the STR fragment analysis showed fetal triploid. The possible cause of this case was double female fertilization, since no maternal contamination was found in amniotic fluid samples. Therefore, this fetal case was considered as the homozygous triploid. The pregnant woman chose to terminate the pregnancy after genetic counseling. In conclusion, the prenatal diagnosis combining with STR fragment analysis can not only eliminate the influence of maternal contamination, but also find chromosome number abnormalities.

Key words: Prenatal diagnosis, Congenital abnormalities, Triploidy, Short tandem repeat, Tandem repeat sequences, Abnormal karyotype