How large a market for prenatal diagnosis by sequencing?

Prenatal diagnosis is one of the most interesting clinical applications of sequencing. The idea behind prenatal diagnosis is that potential disorders that a foetus may have are detected before birth, so that the parents can decide what to do about it. A widespread and ancient technology is ultrasound. An alternative method involves sampling of the amniotic fluid surrounding the foetus with a large needle (amniocentesis), which causes a miscarriage in 1% of cases. More recently genetic screening technologies, including sequencing, have entered the market.

The most prominent company offering prenatal diagnosis by screening is Sequenom. This week, Sequenom announced a public offering of shares valued in excess of $50m. The aim is to finance further expansion of its business, including sales of its MaterniT21 prenatal test.

The principle behind the MaterniT21 test is that some of the DNA in a pregnant woman's blood is of foetal origin. By sequencing that DNA, it is in principle possible to reconstruct most of the genotype of the foetus, and to detect most genetic disorders from the 10th week of pregnancy onwards- earlier than with equivalent tests.

Sequenom's MaterniT21 test currently only returns information on whether there is an third copy of chromosome 21, which causes Down syndrome. If the test returns a positive result, the parents can then decide which actions to take, which could include termination of the pregnancy.

Sequenom is reported to charge $2,700 per test to insurance companies, which is likely to be the cost to them many times over. Therefore there should be plenty of room for prices to come down once there is more competition. That there will be more competition is likely. In the United States, Verinata, which raised $47m in autumn 2011, and TrovaGene are also working on technology based on sequencing foetal DNA from the mother's blood. In Germany, LifeCodexx is developing a similar test, licencing technology from Sequenom.

Even at lower prices, which will probably be paid for by insurers anyway, the big question is how many couples are willing to purchase a test. Of 4.1 million births each year in the US, 750,000 (18%) are judged to be at a high risk of Down syndrome or other chromosomal abnormalities, either because the mother is over 35 years old or because there is a history of such disorders in the family.

It is likely that in the future the tests of Sequenom and its competitors will include other disorders such as cystic fibrosis, muscular dystrophy, anaemia, neuropsychiatric conditions like autism, and beta-thalassaemia. This could widen their appeal to parents that are not in the 18% currently judged as high risk. If prices come down sufficiently, I don't see a reason why sequencing-based tests for pregnant women could not be as prevalent as ultrasound is today.

At 4.1 million births in the US alone each year, and even if the price of tests decreases to a fraction of what they are now, it could well be a multi-billion dollar market.

Time to buy some of those new Sequenom shares?