A young South African man who had the world's first successful penis transplant last December has impregnated his girlfriend, the doctor who led the surgery said on Friday.

The 22-year-old man, who has not been named, is among around 250 South Africans who lose their penises each year in botched traditional circumcisions.

The nine-hour transplant operation formed part of a pilot study by Tygerberg Hospital in Cape Town and the University of Stellenbosch. The patient was sexually active five weeks later.

"To us it means we are ticking most of the boxes where this guy can stand and urinate normally, can have sexual intercourse and his penis function has recovered completely," Andre van der Merwe, who led the surgical team, told Reuters.

"Now to have children is the last thing we wanted."

He said that independent pregnancy or paternity tests have not been done to verify it was indeed the patient's child but he had no reason to disbelieve the young man, who was employed and lived in Cape Town.

"I know that he can ejaculate normally and there is no reason for him to be infertile. I was expecting a pregnancy at some stage, even though I didn't expect it this early," he said.

Each year, hundreds of young South African men, mainly from the Xhosa tribe, lose their penises after coming-of-age rituals go wrong.

It is hoped Van der Merwe's pioneering surgery will help them overcome the physical and psychological trauma.

Announcing the successful transplant in March, Van der Merwe's team said the procedure could eventually be offered to men who have lost their penis to cancer or as a last resort for severe erectile dysfunction.

Van der Merwe has received requests for penis transplants from as far afield as the United States, Colombia and Russia.

"I do believe we will transplant again before the end of the year," he said.