In breakthrough study, researchers from the University of Stanford in California have mapped the entire DNA of an unborn baby using just mother’s blood. The new research could allow doctors to screen a range of genetic diseases in future such as Down’s syndrome and cystic fibrosis.
The new invention brings foetal genetic testing closer to becoming an everyday procedure. For decades, procedures known as amniocentesis or chorionic villus sampling had been done in attempt to learn whether woman’s foetus carried genetic abnormalities. These tests rely on obtaining cells or tissue from the fetus through a needle inserted in the womb.
These procedures could lead to miscarriage in about one in two hundred pregnancies. Besides they also detect only a limited number of genetic conditions. The existing techniques that are used to pick up genetic diseases in unborn babies need invasive sampling, which carries certain risks to the health of the mother and chill.
However, the early diagnosis of such problems can allow doctors to pre-empt whether treatments are required immediately after a baby is born. The latest technique pivots around the fact pregnant women have DNA from both their cells and those of their unborn baby circulating freely in their blood. The amount of circulating foetal DNA increases steadily during pregnancy.
By reaching in the final three months the amount of circulating foetal DNA can be as high as thirty percent of the total. Circulating foetal DNA contains genetic material from both the mother and the father. By comparing the relative levels in the mother’s blood of regions of maternal and paternal DNA known as haplotypes, the researchers were able to identify fetal DNA.
They can even verify which haplotype came from the father lacking of additional paternal information, which may be useful if his DNA is not available. Lead researcher Prof Stephen Quake, explained they are interested in identifying conditions that can be treated before birth, or immediately after. Without such diagnoses, newborns with treatable metabolic or immune system disorders suffer until their symptoms become noticeable and the causes determined.
Because, the cost of such technology continues to drop, the researchers believe it will become increasingly common to diagnose genetic diseases within the first three months of pregnancy. They even showed mapping just the exome, the coding portion of the genome, can provide clinically relevant information.
The Stanford team tried this method in two pregnant women, one of whom with DiGeorge syndrome, a condition caused by a short deletion of chromosome twenty-two, and the other healthy. Their whole genome and exome sequencing showed the child of the woman with DiGeorge syndrome would also have the disorder. The study was reported in Nature.