A High Court judge has agreed to the sterilisation of a man because it is "in his best interests".
It is the first time a UK court has made such a decision.
Referred to as "DE", the 37-year-old has an IQ of 40, meaning he has the mental age of a child aged between six and nine.
The judge said a vasectomy could take place after hearing that DE does not want to become a father again, and another child could cause him "psychological harm".
He already has a young son, born in 2010, with his girlfriend.
Experts said DE was capable of consenting to sexual relationships but could not properly make decisions about contraception.
They said he could not be relied on to use condoms or other birth control methods effectively.
The case came to court because of evidence that DE lacks the capacity to decide whether or not to agree to the sterilisation.
A routine was in place to stop the man meeting his girlfriend without supervision to "keep them safe", the court was told.
Sky News' Senior Correspondent Michelle Clifford, who was at the High Court, said experts believed the man "did not have the power to resist unprotected sex".
There were worries that the man's partner - who also has learning difficulties - could become pregnant again.
Clifford said the first pregnancy had caused "great distress" to the man.
"In the beginning he could not even understand how the birth of the child had anything to do with what he had done.
"He was very unhappy and very disorientated."
The man's mother - as well as expert witnesses - all said he was adamant he does not want another child.
It is hoped the vasectomy will give the man greater independence in his relationship and that he can see his girlfriend without supervision.
A local NHS trust made the application for sterilisation with the support of DE's parents and his GP.
Some critics have said giving consent for the vasectomy could pave the way for sterilisation of other people with learning difficulties.
