The world's tallest man, China's Bao Xishun, became the world's tallest father this week with the birth of his first child, a boy whose initial height seems a compromise between his gigantic dad and average-sized mum.

Bao's son measured 56 centimetres long at birth, the senior doctor at Zunhua Hospital in Hebei province told Reuters.

Although slightly taller than average for newborn children, Bao's boy came up well short of the 75 centimetres claimed as a record birth length last year, also in China.

"Bao is quite happy. The baby is healthy and a normal size," the hospital's senior doctor Zhang told Reuters.

Bao, a 2.36 metres herdsman from Inner Mongolia, last year married Xia Shujuan, a pygmy by contrast at 1.68 metres.

"I hope he or she can be about 2 metres tall," Bao, 57, said last year about his wishes for a child. "Then he or she can play basketball."

His son weighed 4.2 kilograms at birth, a touch heavier than average.

Bao briefly lost his Guinness World Records title as the tallest man to Ukrainian Leonid Stadnyk but regained it in August when Stadnyk refused to be measured under new guidelines.

Bao's son was born on Thursday but news of the birth only spread widely this morning, with the Chinese press according the newborn a level of privacy that is rare for the world's tallest man.

The former goat herder hires himself out for publicity stunts and his wedding last year was sponsored by at least 15 companies.