WASHINGTON Ms Marlo Mack, 43, thought she had given birth to a boy, but at the age of three, her child informed her otherwise.
The single mother, who works as a media professional and is using a pseudonym, recalled of her child's words: "She said, 'Mama, something went wrong when I was in your tummy that made me come out as a boy instead of a girl. Please put me back so I can be a girl.' "
Today, instead of a son, Ms Mack has a seven-year-old daughter, whom she calls M to protect her identity.
The term used to describe M is transgender, referring to a person whose gender identity does not conform to their assigned sex at birth.
The issue was recently debated by parents in Fairfax County, less than an hour from the nation's capital, when the school board there added gender identity to its non-discrimination policy.
A statement released by the board's chairman said the decision would "provide an environment which promotes equality where every student and employee is treated with dignity and respect".
On a practical level, the change means transgender children might soon be able to use toilets that match their gender identity and not their genitalia - an issue that raised the ire of some parents.
The transgender issue has been touted as the civil rights topic of this generation in the United States.
There are podcasts, TV shows and documentaries about it and increased media buzz recently after Bruce Jenner, the patriarch of the reality show Keeping Up With The Kardashians, admitted in an ABC News TV special to being transgender since he was a boy.
In 2012, the American Psychiatric Association revised its Diagnostic And Statistical Manual Of Mental Disorders. It took gender identity disorder off the list of mental disorders.
The association states on its website that a psychological state is considered a mental disorder if it causes distress or disability, and that is not the case with transgender people.
There is little research on transgender children now. While some experts still believe it is a mental condition, others say there is nothing wrong with the child and they should be allowed to live according to their gender identities in a supportive environment.
Doctors and advocates say they have seen more transgender children and their parents come forward over the past decade, with a spike in recent years.
Non-profit group Gender Spectrum, which works with youth and families on gender issues, holds an annual conference for families each year.
In its first year in 2007, the conference involved fewer than 50 people. Last year, there were more than 1,000 attendees.
"It is growing exponentially as people become aware of gender in general and how it affects their kids and youth," said Ms Pam Wool, director of family services and administration at Gender Spectrum.
Doctors and counsellors say children as young as three or four may start to express identification with a different gender than what their parents might have assumed. To many, this seems inconceivable.
But a recent study of transgender children aged five to 12, led by psychological scientist Kristina Olson of the University of Washington, showed that "transgender children are not confused, delayed, showing gender-atypical responding, pretending or oppositional".
She added: "Instead, (they) show responses entirely typical and expected for children with their gender identity."
The report concludes that "transgender children do indeed exist".
But to some, like Professor Paul McHugh, who specialises in psychiatry and behavioural sciences and is former psychiatrist-in-chief at The Johns Hopkins Hospital in Baltimore, the children could just be going through a phase.
Citing studies done in Holland and Britain, he said about 80 per cent to 90 per cent of children will abandon the idea. "It is a psychosocial problem that can be solved," he said.
Prof McHugh likens it to anorexia, where a child might think he or she is fat when that is not the case.
But others believe there is nothing wrong with these children, and they should be able to live their lives according to the gender they identify with.
Rebutting the notion that her child has a mental disease, Ms Mack said: "It is not a disease, she is not rife with anxiety. She is a happy, easy-going child."
Ms Mack said she took a year to come around to the idea that her child was transgender.
"It was terrifying, I knew nothing about it, and I was so sceptical," she said.
"I told her, 'You can love pink, you can be any boy you want to be, but you are a boy,' " said Ms Mack, who continued using "he" to refer to her child for nearly a year.
"She was so miserable," said Ms Mack. "It felt abusive and cruel to call her by the wrong pronoun.
"At a certain point, it is not a choice."
M now lives as a girl. She uses the girls' toilet, has long hair and draws portraits of herself as a little girl in a dress.
In a podcast that Ms Mack puts up occasionally to document her child's life, M tells her mother: "My favourite thing about being transgender is that I am myself now."
This article was first published on May 24, 2015.
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