Men could become pregnant "tomorrow" thanks to advances in womb transplantation, according to a leading fertility expert.
The success of womb transplants into women has paved the way for a similar operation being carried out on people born male, reports The Daily Mail.
Dr Richard Paulson said that now wombs have been successfully transplanted into women born without them, 'trans women' - people born biologically male but who have had sex change surgery - will also want a womb transplant.
This would allow them to carry a baby - and there was no scientific reason why it would not happen, he added.
In recent months, there have been reports of 'trans men' having babies - women who have had sex change operations to become male, but still have functioning wombs.
Dr Paulson, president of the American Society for Reproductive Medicine, made his controversial prediction at the society's annual meeting in San Antonio, Texas.
When asked whether men having babies was "pie in the sky", he said: "You are talking about trans women. Someone who started out as a man, who became a woman.
"There would be additional challenges, but I don't see any obvious problem that would preclude it. I think it would be possible."
Asked when someone who was born male could be fitted with a uterus, Dr Paulson said: "They could do it tomorrow."
He added, however: "It's still a very complicated procedure. It's a huge team, it's not something somebody can do in a community hospital and just get it done."
Dr Paulson explained that one problem is that the male pelvis would not allow a baby to pass through it because it is too narrow, so a man would have to give birth by caesarean section.
But there was room inside a man to hold a womb. Dr Paulson said hormones might have to be given to replicate the changes that go on while a woman is pregnant.
Procuring a uterus would be necessary - either from a living donor or from a brain-dead donor - a complicated, ten-hour operation.
Once the uterus has been transplanted, an IVF embryo would have to be implanted. Dr Paulson said the field of 'trans medicine' has now 'reached the mainstream', adding: "I suspect there are going to be trans women who want to have a uterus and will likely get the transplant."
Womb transplant is still very much an experimental procedure.
The first that resulted in a live birth took place in 2014, carried out by Dr Mats Brannstrom, of the University of Gothenburg in Sweden. The first British attempt at a womb transplant is expected to be carried out next year - on a woman - by Dr Richard Smith of Imperial College London.
In the UK it would be illegal for an IVF clinic to create an embryo for the purpose of implanting it in a man under the Human Fertilisation and Embryology Act 2008.
An international agreement, The Montreal Protocol, also stipulates that womb transplants should be carried out only in biological women.
Julian Savulescu, professor of practical ethics at Oxford University, said womb transplantation represents a 'significant' risk to the foetus and future child.
While there might be a "psychological benefit" to the mother of carrying her own pregnancy, this had to be "weighed against any psychological harm to the child being born in this atypical way".