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Editor’s comment: Prof. Yves Ville: The street light effect of Down syndrome screening in pregnancy. Time to broaden risk assessment in early pregnancy.
Our present prenatal screening and diagnostic approach remains directed predominantly at identifying Down syndrome. However there are far more prevalent and serious conditions that have become amenable to prenatal screening and diagnosis.
While non invasive advanced prenatal screening using cell-free fetal DNA (cff-DNA) has helped to lift taboos and reservations about screening for other genetic anomalies, the incremental risk of a pregnancy loss associated with invasive testing has seemingly come down to 1 in 500 or less. Evans et al therefore question the significance of fair counselling knowing that in addition to 1 in 200 infants carrying a cytogenetic abnormality identifiable by standard karyotype, another 2.5% have a clinically relevant microdeletion or duplication identified by array-CGH and around 1.6% have a copy number variant. The authors provide an argumentative opinion and a plea for offering either chorion villus sampling (CVS) or amniocentesis for an extensive array-CGH examination to all pregnant women as opposed to screening non-invasively with cff-DNA in maternal blood.
In addition to genetic and cytogenetic abnormalities and variations, more than 7,000 children are born every year in the USA with a disease caused by congenital cytomegalovirus (cCMV) infection, a far greater number than other disorders for which screening and interventions are available, including Down’ syndrome, spina bifida, Fetal alcohol syndrome, congenital rubella, toxoplasmosis and HIV. To date, there is no national health system recommending screening for cCMV neither prenatally or even at birth. The reasons usually given include the uncertainty of the prognosis of a infected fetus and the lack of prenatal treatment. In this issue of AJOG, Leruez-Ville et al show that risk assessment of infected fetuses for being symptomatic at birth is possible as early as the time of diagnosis by using a combination of targeted ultrasound examination along with viral load in amniotic fluid and in fetal blood together with platelet count. The advantage of using amniotic fluid is that it is available at prenatal diagnosis.
The continued rapid increase in the field of screening and prenatal diagnosis calls for a paradigm shift in the field of prenatal diagnosis. However, the severity of the phenotype of the targetted anomalies does vary and these inevitable changes are fraught with new expertise needed in order to avoid iatrogenic and eugenic drift.