So she turned to what was then a more controversial idea: testing for DNA damage in the man’s sperm. By that point, a growing body of research had linked DNA fragmentation in sperm to an increased risk of miscarriage. The guidelines stop short of outright recommending the tests; instead they say more research is needed to determine whether treatments for reducing sperm DNA fragmentation improve pregnancy outcomes. Sakkas conducted research in the 1990s that looked at the DNA of sperm from men with fertility problems and found little breaks in the molecules’ structure. Sakkas predicts that consensus will shift toward more proactively testing sperm in the case of repeat miscarriage, especially as companies offer increasingly sophisticated and lower-cost DNA testing.