The child was critically ill. The treating team at Children's National Hospital in Washington, DC, was stumped and worried that time was running out. Every test was coming back negative.

Genetics was called in to look for chromosomal mutations that might suggest the source of the problems. The geneticist recommended whole-exome sequencing, which tells a story based not only on all of the child's genes, but on two additional sources as well: the mother's and the father's genes.

They found something they weren't looking for. The father, the worried man in the waiting room who raised this child, wasn't the biological father. In genomics it's called an "incidental finding," and it raises huge ethical questions: Do you reveal this to the parents? Only to the mother? Or, if the results don't affect the child's care, do you even tell anyone?

In this case, the team called on the hospital's ethics committee for help.

Monisha Samanta Kisling, MS

"What made it really complicated here is that the father was actually the primary caregiver and was really, really involved with the child," explains Monisha Samanta Kisling, MS, a genetic counselor who has worked at Children's National for 7 years. Plus, the father was the legal parent and responsible for the family as a provider, including securing the child's health insurance. Disclosing this information could have a lasting, lifelong effect.

"He has dedicated his life to and does everything for the child. You're really at risk of causing potential serious conflict for this family, and potentially for this kid who really needs that support system," Kisling says.

If you think this scenario is an outlier, you're mistaken. Various studies have estimated rates of false paternity at between 1% and 10%.[1]

'Incidental' Yet Deeply Significant

The field of genomics calls misattributed paternity — or in some cases, simply paternity — a "secondary" or incidental finding. Perhaps, but it's certainly difficult to ignore.

"In a lot of cases, it's just very hard to hide that information with the report that you have," Kisling explains, because the variants that a geneticist discovers in the child's DNA don't match up at all with the father's genes. "If the child didn't inherit any of the variance from the father, that would throw in some question marks, right?"

Paternity might be incidental, but it's clearly significant. This information — whether a father is truly a child's biological father — can change families in an instant.

Whether to disclose poses a dilemma that can feel fraught. Telling a man that he's not the father of his child can have devastating consequences: He might leave the family. The standard in pediatrics is to practice medicine "in the best interest of the child"[2]; first and foremost is the child's well-being. That means keeping the focus on the child and their future.

Still, because there are really no data about how these shocking disclosures affect families, doctors are truly in the dark about how to handle these tricky scenarios.

"It's hard to make these decisions because we may not know the families that well. We don't necessarily know what's the right decision for them," Kisling says. She believes clinics should approach each family with fresh eyes, because every couple is different.

"I think withholding information can feel paternalistic," Kisling says. "We don't want to say, 'Hey, I don't think you can handle this information.' That's not necessarily our judgment call to make. Overall, it's just a really, really tough decision."