Duo test and aneuploidy detection in women under 35 years of age with high-risk pregnancy at the Hospital General de México

Non-invasive procedures for prenatal diagnosis are the most frequently used methods in the first trimester of pregnancy in pregnant women under 35 years of age because they do not involve risk of pregnancy loss; however, they are not considered to be a definitive diagnosis method. During the first trimester the duo test (PAPP-A and free βhGC), cell-free fetal DNA in maternal blood and structural ultrasound scans are the principal tools used; the quadruple marker test (αFP, E3, β-hCG, inhibin A) is used in the second trimester. However, the definitive diagnosis is performed by cytogenetic analysis through amniocentesis.

Methods

Thirty women, under 35 years of age with high-risk pregnancy, were studied with duo test and structural ultrasound in the first trimester and amniocentesis in weeks 15–18.

Results

Only five duo tests were positive: three showed risk of trisomy 18 and one of Turner syndrome, they all corroborated with the cytogenetic study; the fifth showed a risk of Down's syndrome, however it was a chromosomally normal product. Three patients with a negative duo test cytogenetically detected with karyotypes with structural abnormalities, which were: deletion of the short arm of chromosome 18 [46,XY, del(18)(p11)], Robertsonian translocation between chromosome 13 and 14 [45,XY, rob(13:14)] and a chromosome derived from X [46,X, der(X)]. The duo test is a very useful tool for the diagnosis of numerical chromosome abnormalities, but not for detecting structural chromosome aberrations. However, it is essential to perform amniocentesis to definitively rule out chromosomal aberrations in products of conception.