BACKGROUND Screening for trisomy 21 by a combination of maternal age, fetal nuchal translucency (NT) thickness and maternal serum free beta-hCG and pregnancy associated plasma protein-A (PAPP-A) at 11-13(+6) weeks of gestation is associated with a detection rate of 90%, for a false-positive rate of 5%. Recent evidence suggests that in about 70% of fetuses with trisomy 21 the nasal bone is not v...

Down syndrome is a collection of features that are caused by trisomy for human Chromosome 21. While elevated transcript levels of the more than 350 genes on the chromosome are primarily responsible, it is likely that multiple genetic mechanisms underlie the numerous ways in which development and function diverge in individuals with trisomy 21 compared to euploid individuals. We consider genotyp...

Down syndrome (DS) or trisomy 21 is the most common genetic disorder with a prevalence of 1 in 660 live births [1]. In 1959, Lejeune and colleagues discovered the genetic basis of DS and named as trisomy of chromosome 21, which is the smallest human autosomal chromo‐ some [2]. Trisomy 21 can occur as three types of chromosomal abnormalities: free trisomy 21, translocation or mosaicism. Free tri...

Prenatal screening is often misconstrued by patients as screening for trisomy 21 alone; however, other chromosomal anomalies are often detected. This study aimed to systematically review the literature and use diagnostic meta-analysis to derive pooled detection and false positive rates for aneuploidies other than trisomy 21 with different prenatal screening tests. Non-invasive prenatal testing ...

John Hilton Edwards [7] first described the symptoms of the genetic disorder known as Trisomy 18?one of the most common forms of human trisomy, which occurs when cells have an extra copy of a chromosome, in 1960. Trisomy 18 [5], also known as Edwards Syndrome [6], occurs approximately once per 6000 live births and is second in frequency only to Trisomy 21, or Down?s Syndrome, as an autosomal tr...

OBJECTIVE The study aimed to validate the efficacy of detection of fetal cell-free DNA in maternal plasma of trisomy 21, 18 and 13 in a clinical setting. METHODS A total of 2340 women at high risk for Down syndrome based on maternal age, prenatal history or a positive sesum or sonographic screening test were offered prenatal noninvasive aneuploidy test. According to the prenatal noninvasive a...