Biochemical screening for aneuploidy

Biochemical and ultrasound methods for risk adjustment of fetal aneuploidy have replaced maternal age as the mainstay of prenatal care. This development has been accompanied by much confusion and inconsistent results. However, the totality of available data support the conclusion that, as of 2007, optimal biochemical detection can be achieved in the first trimester using free β−human chorionic gonadotropin and pregnancy-associated plasma protein-A, and for greater sensitivity the biochemistry needs to be combined with ultrasound nuchal translucency measurement. Even better results might be obtained by testing women sequentially in both trimesters, but this approach has the disadvantage of delaying diagnosis for many women. An alternative, in appropriately trained centers, is to carry out sequential testing within the first trimester using nasal bone determination and other secondary ultrasound markers to complement nuchal translucency measurements.