Impacto de la introducción en el primer trimestre del cribado combinado de trisomía 21 en la tasa de procedimientos invasivos

Objective

To study the impact of introducing first-trimester combined Down syndrome screening on invasive prenatal testing for prenatal diagnosis, together with the criteria change from 35 to 38 years old as the indication for obtaining the fetal karyotype.

Material and methods

A retrospective population-based study was carried out of invasive tests for prenatal diagnosis performed at the Cabueñes Hospital in Gijón (Spain). A first period from 31-1-2004 to 30-1-2006 (without the screening program) was compared with a second period from 31-1-2006 to 30-1-2008 (with the screening program). During the second period the impact of screening (31-1-2006 to 30-1-2007) was differentiated from that linked to changing the maternal age criteria to 38 years old as the indication for invasive testing (31-1-2007 to 30-1-2008).

Results

During the second period there was an overall reduction of 31.2% in invasive testing; 21.6% was exclusively attributable to first-trimester combined Down syndrome screening. In expectant mothers aged 35 or more at delivery, the number of amniocentesis performed in the second period was reduced by 30.74%; this tendency was maintained for pregnant women aged 38 years or more, showing a reduction of 25.92%. In the second period, 30% of the expectant mothers aged 38 years or more chose to have an invasive test due to their age compared with 61.53% in the first period.

Conclusions

First-trimester combined Down syndrome screening had a major impact on invasive testing, increasing its efficiency and, moreover, allowing detection rates to be improved.