What was once considered a ground-breaking US study to track the health of children from birth to adulthood may be stopped before its official start, causing alarm for advocates and researchers who say its findings are crucial to developing prevention strategies for childhood illnesses like asthma, autism, and attention deficit disorder.

The National Children’s Study, a 21-year longitudinal study of 100,000 children, was set to start this year. Its implementation, though, has snagged on concerns that it’s based on costly and antiquated research methods, and that it has been plagued by mismanagement.