Blood test for pregnant women can predict premature birth

A new blood test for pregnant women detects with 75-80 percent accuracy whether their pregnancies will end in premature birth. The technique can also be used to estimate a fetus's gestational age -- or the mother's due date -- as reliably as and less expensively than ultrasound. Developed by a team of scientists led by researchers at Stanford University, the tests could help reduce problems related to premature birth, which affects 15 million infants worldwide each year. Until now, doctors have lacked a reliable way to predict whether pregnancies will end prematurely, and have struggled to accurately predict delivery dates for all types of pregnancies, especially in low-resource settings. The blood tests are described in a paper that will be published online June 7 in Science. Stephen Quake, PhD, professor of bioengineering and of applied physics at Stanford, shares senior authorship with Mads Melbye, MD, visiting professor of medicine. The lead authors are former Stanford postdoctoral scholar Thuy Ngo, PhD, and Stanford graduate student Mira Moufarrej. "This work is the result of a fantastic collaboration between researchers around the world," said Quake, who is also the Lee Otterson Professor in the School of Engineering. "We have worked closely with the team at the Stanford March of Dimes Prematurity Research Center, and the research involved collaborations with scientists in Denmark, Pennsylvania and Alabama. It's really team science at its finest." The tests measure the activity of maternal, placental and fetal genes by assessing maternal blood levels of cell-free RNA, tiny bits of the messenger molecule that carry the body's genetic instructions to its protein-making factories. The team used blood samples collected during pregnancy to identify which genes gave reliable signals about gestational age and prematurity risk. "We found that a handful of genes are very highly predictive of which women are at risk for preterm delivery," said Melbye, who is also president and CEO of the Statens Serum Institute in Copenhagen. "I've spent a lot of time over the years working to understand preterm delivery. This is the first real, significant scientific progress on this problem in a long time." Largest cause of infant mortality in U.S. Premature birth, in which a baby arrives at least three weeks early, affects 9 percent of U.S. births. It is the largest cause of infant mortality in the United States and the largest contributor to death before age 5 among children worldwide. In two-thirds of preterm births, the mother goes into labor spontaneously; doctors usually do not know why. Previously, the best available tests for predicting premature birth worked only in high-risk women, such as those who had already given birth prematurely, and were correct only about 20 percent of the time. Quake first became interested in this problem when he became a parent: his daughter was born nearly a month premature. "She's now a very healthy and active 16-year-old, but it certainly stuck in my mind that this is an important problem to work on," Quake said. Doctors also need better methods for measuring gestational age, he added. Obstetricians now use ultrasound scans from the first trimester of pregnancy to estimate a woman's due date, but ultrasound gives less reliable information as pregnancy progresses, making it less useful for women who don't get early prenatal care. Ultrasound also requires expensive equipment and trained technicians, which are unavailable in much of the developing world. In contrast, the researchers anticipate that the new blood test will be simple and cheap enough to use in low-resource settings.