A big experiment aimed at finding out if it pays off to screen newborns for hundreds of potential genetic diseases has come back with an answer: maybe.

Researchers say they found an unexpectedly high number of potentially disease-causing mutations in a subset of 159 babies they tested. What they don’t know is how much useful information the testing provided for the babies or their parents.

One baby turned out to have a vitamin deficiency. Another, in the neonatal intensive care unit with respiratory distress, carried a gene that raises the risk of cancer. Still others carried hard-to-interpret genes that may raise the risk of heart disease in years to come.

The researchers taking part in the study say it’s too soon to recommend such wide genetic testing for the general public. But they say their findings suggest that in some cases, and for some people, it may be worth doing.

“This is a kind of glass half full, glass half empty situation. On one hand, you are identifying those babies as at-risk and we know many of them will never develop the disease in question,” said Dr. Robert Green, a professor of medicine at Harvard Medical School and Brigham and Women’s Hospital, who worked on the study.

“On the other side, you're identifying disease risks which are actually actionable, you can do something about. So these babies can be monitored … and you can actually look for these conditions and try to prevent them or mitigate them,” Green told NBC News.

Green and colleagues are testing newborns for about 5,000 different genetic variations linked with disease as part of a larger project called BabySeq. Their report on what they found in 159 of those babies is published in the American Journal of Human Genetics.

Just over 9 percent of the babies had genetic sequences that could put them at risk of diseases that might appear during childhood, such as hearing loss or heart defects. One had immediate symptoms linked with the genetic sequence: Cora Stetson, now 2, has a genetic tendency to be deficient in biotin, an important B vitamin.

Other tests showed that Cora did indeed have low levels of biotin, something easily corrected with a daily supplement. “So we give her a supplement every night with dinner. We put it in yogurt,” Lauren Stetson, her mother, who lives outside Boston, told NBC News.

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Without biotin, Cora’s development could have been affected. “She could have had just decreased vision, maybe trouble hearing, cognitive problems,” Stetson said. “She may just have struggled in school and we'd may just have said, ‘oh well, she just has a hard time learning’ or ‘she just needs glasses’ or any of those things,” she added.

“But is so easily fixed for us now that we know that's exactly what's going on.”

Green counts Cora as a success. “So, I'd like to think when this baby's in college we may have contributed to her good grades,” he said.

Most of the other cases, however, were fuzzier. Only a handful of parents signed up for the testing, and they did not always get clear answers to questions. A girl born with respiratory distress had a genetic variant linked to Lynch syndrome, which puts people at high risk of various cancers throughout life. A boy born with a narrowed heart artery had a genetic defect linked with a red blood cell disorder. They were among 32 babies in the NICU who were tested as part of the project.

“One of the things they did not see in this paper was they did not get an unequivocal answer for those families. There were families who wanted testing to answer the question of why their baby was sick, and some of those families did not get answers,” said Heather Zierhut, associate director of the Genetic Counseling Program at the University of Minnesota, who was not involved in the study.

That tells Dr. Wendy Chung that this kind of testing is not ready for wider use.

“Most (parents) probably got knowledge that wasn’t useful for a newborn baby,” Chung, an expert in pediatric genetics at Columbia University, told NBC News. “It’s not what we need to be doing right now. It’s not what parents want.”

Babies are already screened at birth for genetic diseases that could kill them or make them very ill in early childhood. The first test was for phenylketonuria, caused by a genetic defect that causes brain damage if patients do not eat special diets. Most states mandate a panel of such tests at birth.

Chung took part in a project that led to widespread testing for a genetic condition called spinal muscular atrophy. It’s a serious condition but treatments are available, Chung said. “We identified newborns in that study who absolutely their lives were saved,” she said. “They got immediate access to treatment that prevented them from developing symptoms.”

Green and colleagues tested for cancer-causing genes as part of their study. In one case, they were able to tell the mother of one of the children who tested positive for one such gene that she also carried the mutation. Chung worried about the effects on a child who tested positive for a mutation in BRCA1 or 2, which raises the risk of breast and ovarian cancer, as well as prostate cancer.

“It is not clear to me, for instance, if you have a BRCA mutation that you should be living under that cloud when you are growing up as a kid,” she said.

Green agreed that care is needed.

“We're very aware that the more you look at these genomes, the more variation you're going to find and to some degree we can be exposing these babies to excessive medical intervention,” he said. “They could get x-rays. They could get invasive tests. They might get surgery that they don’t need.”

One of the most common genetic risk factors that was found could lead to heart defects in childhood. “What is it like to live with uncertainty (such as) could my child have a heart condition that could lead to sudden death?” asked Zierhut.

Green has an answer. “That allows you to monitor the baby, to look for those symptoms early, to maybe examine their heart in some non-invasive way,” he said. “Maybe (a doctor) will listen just a little more carefully to the heart each time the baby comes in and maybe if there is a murmur or an abnormality in the heart, they'll detect it just a little bit earlier because of the DNA testing.”

The babies in the study will be followed for years to see what diseases, if any, they do develop.

"We plan to follow these babies, as well as their parents and their doctors, to look at how this information gets used and how it impacts health and well-being long term,” said Casie Genetti, a genetic counselor at Boston Children's Hospital who took part in the study.

“We would have to follow these babies for years, even decades, to know fully whether the condition in question is going to affect their health,” agreed Green.

The testing was worth it to Stetson. “The benefit of the tests outweighed the risks,” she said. “It was something that we felt could potentially help our child. I don't think ignorance is bliss.”