Americans conceived through sperm donation also are more likely to feel alienated from their immediate family than either biological or adopted children. They’re twice as likely as adoptees to report envying peers who knew their biological parents, twice as likely to worry that their parents “might have lied to me about important matters” and three times as likely to report feeling “confused about who is a member of my family and who is not.”

And the realities of commercialized reproduction — in which desirable donors can father dozens of children by different mothers, creating far-flung networks of half-siblings who will never know each other — weigh heavily on them. They are more likely than adoptees to say that “when I see someone who resembles me, I often wonder if we are related,” for instance, and much more likely to worry about accidentally falling into a romantic relationship with a relative…

Despite their reputation for permissiveness, many European nations have done much more than the supposedly socially conservative America to recognize that children as well as adults have an interest in the way assisted reproduction works. Britain, Sweden, Norway and Switzerland have banned anonymous sperm and egg donation, allowing donor-conceived children access to their family histories once they turn 18. Many countries also have limited the number of children a sperm donor can father to well below the 25 that the American Medical Association recommends.