A transgender man living in Portland, Oregon, has given birth to a boy with his partner of seven years, Biff Chaplow.

Trystan Reese, 34, was born a girl - but despite beginning hormone therapy a decade ago, he has kept his original anatomy, enabling him to get pregnant.

Their son, Leo Murray Chaplow, was born July 14.

Now, after experiencing the heartbreak of a miscarriage last year, he and his husband Biff Chaplow have finally welcomed their first biological child, news.com.au reported.

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Mr Reese and Mr Chaplow told CNN that Leo "eats like a champ, sleeps well, and gives us lots of cuddles."

"We are so lucky to have been able to welcome him into our lives and cannot wait to see who he grows up to be," they said.

Mr Reese told CNN that he had stopped taking testosterone to prepare for the pregnancy.

"We've been under medical supervision the entire time," he said, "to make it as healthy and safe as possible."