Germany has become Europe's first country to allow babies with characteristics of both sexes to be registered as neither male nor female.
Parents are now allowed to leave the gender blank on birth certificates, in effect creating a new category of "indeterminate sex".
The move is aimed at removing pressure on parents to make quick decisions on sex assignment surgery for newborns.
However, some campaigners say the new law does not go far enough, the BBC reports.
As many as one in 2,000 people have characteristics of both sexes.
They are known as intersex people because they have a mixture of male and female chromosomes or even genitalia that have characteristics of both genders.