Scientists say a new blood test for pregnant women could identify thousands of serious genetic conditions in a developing foetus, potentially reducing the need for invasive prenatal screening.
The test, set to be presented at the European Society for Human Genetics conference in Gothenburg on Saturday, analyses tiny fragments of foetal DNA circulating in the mother’s bloodstream. Using advanced sequencing and computing methods, researchers say it can detect a high proportion of genetic disorders, including cystic fibrosis, that are currently usually confirmed through amniocentesis or other invasive procedures.
Known as non-invasive foetal sequencing (NIFS), the technique could offer a safer and similarly accurate screening option in pregnancy, according to Dr Christopher Whelan, a senior computational scientist at the Broad Institute of Massachusetts Institute of Technology and Harvard University.
Whelan said the test is capable of identifying thousands of serious genetic conditions, including most of those included on major newborn sequencing and foetal anomaly panels, such as Genomics England’s panel of more than 2,500 genes linked to foetal anomalies.
He added that the validation study detected conditions including Noonan syndrome, CHARGE syndrome, Stickler syndrome, achondroplasia and many other rare genetic disorders where early diagnosis could influence pregnancy management, delivery planning or newborn care.
Non-invasive prenatal tests based on foetal DNA have already transformed screening, but until now have mainly been limited to a small number of conditions, such as Down’s syndrome. If further confirmed, the new method could expand screening to almost all genetic conditions included in newborn screening programmes.
Whelan said NIFS could be used as an initial test when an ultrasound or another screening result suggests a possible foetal anomaly. Many pregnant women currently decline invasive procedures such as amniocentesis and chorionic villus sampling (CVS) because of miscarriage risk, stress, access barriers and cost, despite their strong diagnostic capability.
Amniocentesis, usually carried out between the 15th and 20th weeks of pregnancy, involves using a thin needle to collect amniotic fluid. It is highly accurate, but carries a miscarriage risk of about one in every 200 pregnancies.
In the study, researchers used NIFS in 565 pregnancies at an average of 17 weeks’ gestation. By sequencing small fragments of DNA and applying advanced computing methods, they identified genetic variants across nearly 23,000 genes in each foetus. When compared with results from amniocentesis or CVS, the test detected 95% to 99% of the variants found by invasive testing and more than 97% of clinically relevant variants.
Prof Alexandre Reymond of the University of Lausanne, who was not involved in the research, said sequencing an entire foetal genome without taking a direct sample was a major scientific achievement that could open new opportunities for treatment and prevention and transform reproductive medicine.
Prof Angus Clarke, a clinical geneticist at Cardiff University, described the work as a highly impressive technical achievement, particularly in cases where a genetic condition is suspected and prenatal treatment may be possible.
Clarke also warned that using the test for broad exploratory screening could identify genes of uncertain significance, creating anxiety for parents and potentially leading to unnecessary monitoring or medical intervention. He said that without a specific clinical concern, generating possible answers can create additional problems for families.