How well do you know your sperm donor?
His profile says he's 6' 1", a software engineer who does triathlons and enjoys reading Nietzsche.
But what about his ticker?
A sperm donor passed on a potentially deadly heart defect to 9 of the 24 children he fathered, according to an editorial in the Journal of the American Medical Association.
The San Francisco sperm bank affected now gives electrocardiograms to all potential donors. The report's authors say the findings point to the need for more rigorous screening.