A friend posted an article to Facebook with a puzzling title: “Telling parents they’re not a child’s biological mother or father can do more harm than good, expert warns.” If the article were talking about revealing DNA test results to a child, that makes much more sense, one might think, than if they are talking about revealing the results to the parents. That seems to be where this is going, though.

Advances to genetic testing have led to medical experts questioning what they should, and shouldn’t tell parents.

And the ethical dilemma for medical professionals is likely to become more common as genetic testing more more widespread.

I mean, it’s obvious how a guy might not know he is a child’s father, but wouldn’t you think anyone with female reproductive organs would know?

As it turns out, it is entirely possible for someone to believe they are the biological mother of a child who is not actually theirs. One possible way is simple human error, which it turns out is not just a hackneyed comedy premise:

Two mothers in South Africa have discovered they are raising each other’s daughters after they were mistakenly switched at birth in a hospital four years ago.

But while one of the women wants to correct the error and reclaim her biological child, the other is refusing to give back the girl she has raised as her own, posing a huge legal dilemma.

The children in question are now four years old, so there certainly is an argument in favor of leaving well enough alone. The children only know the people who have raised them, after all.

A considerably stranger case involves a woman who gave birth to two children who, despite being conceived and gestated in, then delivered from, her uterus, are not her biological children because of some very odd biology. She was charged with welfare fraud after the DNA tests showed that someone else was the mother, but that’s not the strange part:

Further DNA analysis showed that Fairchild was more like an aunt to her children than a mother, but Fairchild didn’t have a sister. Then, the discovery of a similar case in Boston brought to light another possibility.

Thanks to a rare genetic condition, it turned out that Fairchild was a chimera — essentially a twin in her own body.

You might be a chimera, too. Biology is complicated.