NEW YORK, United States (AFP) — More than 730 people aged five to 76 have changed gender on New York birth certificates since 2015, an explosion in applications after rules were relaxed two years ago, officials said Thursday.

The 731 gender-change applications approved since January 2015 come in stark contrast to about 20 a year prior to the process becoming easier.

Fifty-five per cent changed from male to female, while 45 per cent changed from female to male, said the city’s health department. Forty-one of the 731 were under the age of 18 and did so with parental consent.

“As jurisdictions around the country continue to adopt policies of discrimination against transgender people, it is crucial for this city to reaffirm its commitment to equality,” said health commissioner Mary Bassett.

On February 22, the Trump administration overturned rules requiring public schools to let transgender students use bathrooms matching the gender with which they identify, rather than the one on their birth certificate.

On Monday, transgender activists got an additional setback when the Supreme Court sent a rights case back to a lower court for reconsideration. A Virginia high school boy is suing to use the boys’ restroom.

New York — America’s largest and one of its most liberal cities — last year issued the first US birth certificate marked “intersex.”

In 2014, the city council approved amendments that meant birth certificate gender-change applicants no longer had to change their name legally and undergo “convertive” surgery.

An applicant can now instead submit an affidavit from a licensed medical or mental health provider.