Jim Burroway analyzes a longitudinal study finding that the children of lesbian parents do better than the children of heterosexual parents. His caveat:
This study is one of the very few to suggest more positive outcomes [for children of lesbian parents] than children from heterosexual families, a claim that would require more research before it could be regarded as anything more than an outlier. But it’s easy to imagine one reason for this surprising finding. These parents were recruited because they were about to undergo artificial insemination. This means that in every case, these children were brought into the world because they were wanted and planned for. None of them are the product of a drunken tryst in the back seat of a Chevy. These mothers had to investigate options, invest money, and really want to become mothers. This alone can account for the difference.
(Image from here.)