"Pregnancies are usually about  weeks and a premature birth is when a baby arrives three or more weeks early. This happens in about  of all deliveries and it can be seriously risky for the infant https they can have all kinds of complications including lung problems brain hemorrhages and infections. However a new blood test  which is still experimental and not yet available outside of a research lab  can pick up on gene activity in the body that suggests a pregnancy is at risk for preterm delivery according to a study published Thursday in the journal Science httpscience.sciencemag.orglookupdoi.science.aar. The researchers also found a similar type of blood test could determine gestational age which is used to calculate the due date of the baby. Currently gestational age is calculated in the first trimester using ultrasound and its not that accurate if used later in pregnancy. Both tests use cellfree RNA cfRNA which are snippets of genetic material released by cells when genes are active. They float around in the mothers bloodstream and can be picked up by blood tests.  Those molecules will circulate in the blood for some time they can be measured and you can see the contributions from essentially every tissue in the body senior investigator Stephen Quake told BuzzFeed News. When you are pregnant you can see the contribution from the placenta and the fetus said Quake a professor of bioengineering and applied physics at Stanford University in Palo Alto California. The scientists analyzed  genes to find the ones that were active during pregnancy and labor.  They identified seven cfRNAs that seemed to be associated with premature birth and in a test of  women they found that they could predict premature birth up to two months in advance. All the women were at risk for premature labor because they had early contractions or a previous preterm delivery and  did indeed go on to have a premature baby.  In a subgroup of women the test accurately classified  of  preterm deliveries as being atrisk and incorrectly suggested that  of  women who had a fullterm pregnancy were at risk for early labor. In a test of  healthy pregnant women testing for nine cfRNAs seemed roughly as accurate as an ultrasound at measuring gestational age. An ultrasound has a  accuracy rate at predicting a due date thats within two weeks of a babys actual birth while the blood test was  accurate. The test if it does turn out to work in clinical trials would be cheaper than ultrasound said Quake. It might be tens or hundreds of dollars rather than thousands he said. Theres a lot more work to be done before these tests becomes available including clinical trials. The studies were small and included only black or white women but not other ethnicities. But the findings are promising particularly because premature delivery is such a serious problem. Preterm birth is the leading cause of neonatal death its a huge problem Quake said. If doctors know someone is at risk for premature labor earlier in pregnancy they might start efforts to help delay labor such as recommending bed rest. Quake became interested in the problem in part because his first child was born almost a month premature. Shes now a healthy yearold. You realize holy cow that was a pretty risky thing that we had no control over and no sense that it was coming he said. Wed like to see a bunch of lives saved thats really the goal here Quake said. Theres a lot of work left to do before we get to that point but we are pretty energized and excited at this point. The study was funded by the March of Dimes and other nonprofit sources although Quake and his colleagues have filed for a patent on the test."