After those tiny blood spots are tested for a list of devastating diseases, some states are storing them for years. Scientists consider the leftover samples a treasure, both to improve newborn screening and to study bigger questions, like which environmental toxins can harm a fetus’ developing heart or which genes trigger childhood cancers.

But seldom are parents asked to consent to such research — most probably do not know it occurs — raising privacy concerns that are shaking up one of public health’s most successful programs. Texas is poised to throw away blood samples from more than 5 million babies to settle a lawsuit from parents angry at what they call secret DNA warehousing. A judge recently dismissed a similar lawsuit in Minnesota.