Introduction:

The prenatal investigation of chromosomal abnormalities through the use of epidemiological and echographic markers on the first trimester, allows to identify pregnant women with an increased risk of Down syndrome.

Objectives:

To analyze maternal age, nuchal translucency, venous ductus and nasal bone, during the first trimester screening, in pregnant women who underwent prenatal cytogenetic diagnosis, in order to evaluate effectiveness in early detection of Down syndrome and the value for reducing the number of invasive tests.

Methods:

A descriptive retrospective cross-sectional study was carried out and a sample of 3439 pregnant women was studied. The cytogenetic study ordered at Havana Provincial Center for Medical Genetics was carried out from January 3, 2006 to December 30, 2008.

Results:

Advanced maternal age showed 87% sensitivity and 99% of false positive rate. Nuchal translucency accounted 10% of sensitivity. The nasal bone showed no association with positive karyotypes for Down syndrome. A statistical association of the venous ductus presence could not be established since the search was not systematically.

Conclusions:

The estimation of Down syndrome risk based solely on advanced maternal age determines high false positive rate. Therefore, this marker, together with the evaluation of the first trimester ultrasound markers for recalculating the individual risk, can increase the diagnostic effectiveness and decrease the number of invasive tests.

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