A New York City law allowing parents to obtain birth certificates for their children without listing a specified gender took effect this week.

The law allows parents to select the letter “X” signifying a newborn’s gender, and allows adults to switch their gender on their birth certificates to the letter “X” to represent their “true gender identity,” the Associated Press reported.

New York City Mayor Bill de Blasio passed the legislation allowing the “X” option in October, stating that having a third gender is necessary “because everyone deserves to live their truth.”

In New York City we believe that you should be you. That's why we added a third gender to birth certificates — because everyone deserves to live their truth. If you're not out or can't come out, always know that New York City welcomes you the way you are. #NationalComingOutDay pic.twitter.com/i8zBqmtmNb — Mayor Bill de Blasio (@NYCMayor) October 11, 2018

“Should everyone be able to tell their government who they are and not the other way around? That’s why this is so important,” the Democrat mayor told reporters at a press conference

New York City is the first local government entity to pass such a law, although several states— including New Jersey, California, Washington, and Oregon— have similar laws on the books.

The state of Colorado, which recently allowed residents to mark “X” as their gender on driver’s licenses, is also in the process of determining whether it would allow a third gender option on documents such as birth certificates.