Scientists have created prototypes made out of cells extracted from women's bodies. Embryos successfully attached themselves to the walls of these laboratory wombs and began to grow. However, experiments had to be terminated after a few days to comply with in-vitro fertilisation (IVF) regulations.
'We hope to create complete artificial wombs using these techniques in a few years,' said Dr Hung-Ching Liu of Cornell University's Centre for Reproductive Medicine and Infertility. 'Women with damaged uteruses and wombs will be able to have babies for the first time.'
The pace of progress in the field has startled experts. Artificial wombs could end many women's childbirth problems - but they also raise major ethical headaches which will be debated at a major international conference titled 'The End of Natural Motherhood?' in Oklahoma next week.
'There are going to be real problems,' said organiser Dr Scott Gelfand, of Oklahoma State University. 'Some feminists even say artificial wombs mean men could eliminate women from the planet and still perpetuate our species. That's a bit alarmist. Nevertheless, this subject clearly raises strong feelings.'
Liu's work involves removing cells from the endometrium, the lining of the womb. 'We have learnt how to grow these cells in the laboratory using hormones and growth factors,' she said.
After this Liu and her colleagues grew layers of these cells on scaffolds of biodegradable material which had been modelled into shapes mirroring the interior of the uterus. The cells grew into tissue and the scaffold dissolved. Then nutrients and hormones such as oestrogen were added to the tissue.
'Finally, we took embryos left over from IVF programmes and put these into our laboratory engineered tissue. The embryos attached themselves to the walls of our prototype wombs and began to settle there.'
The experiments were halted after six days. However, Liu now plans to continue with this research and allow embryos to grow in the artificial wombs for 14 days, the maximum permitted by IVF legislation. 'We will then see if the embryos put down roots and veins into our artificial wombs' walls, and see if their cells differentiate into primitive organs and develop a primitive placenta.'
The immediate aim of this work is to help women whose damaged wombs prevent them from conceiving. An artificial womb would be made from their own endometrium cells, an embryo placed inside it, and allowed to settle and grow before the whole package is placed back in her body.
'The new womb would be made of the woman's own cells. so there would be no danger of organ rejection,' Liu added.
However, her research is currently limited by IVF legislation. 'The next stage will involve experiments with mice or dogs. If that works, we shall ask to take our work beyond the 14-day limit now imposed on such research.'
A different approach has been taken by Yoshinori Kuwabara at Juntendo University in Tokyo. His team has removed foetuses from goats and placed them in clear plastic tanks filled with amniotic fluid stabilised at body temperature. In this way, Kuwabara has kept goat foetuses alive and growing for up to 10 days by connecting their umbilical cords to machines that pump in nutrients and dispose of waste.
While Liu's work is aimed at helping those having difficulty conceiving, Kuwabara's is designed to help women who suffer miscarriages or very premature births. In this way Liu is extending the time an embryo can exist in a laboratory before being placed in a woman's body; Kuwabara is trying to give a foetus a safe home if expelled too early from its natural womb.
Crucially, both believe artificial wombs capable of sustaining a child for nine months will become reality in a few years.
'Essentially research is moving towards the same goal but from opposite directions,' UK fertility expert Dr Simon Fishel, of Park Hospital, Nottingham, said. 'Getting them to meet in the middle will not be easy, however. There are so many critical stages of pregnancy, and so many factors to get right. Nevertheless, this work is very exciting.'
It also has serious ethical implications, as Gelfand pointed out. 'For a start, there is the issue of abortion. A woman is usually allowed to have one on the grounds she wants to get rid of something alien inside her own body.
'At present, this means killing the foetus. But if artificial wombs are developed, the foetus could be placed in one, and the woman told she has to look after it once it has developed into a child.'
In addition, if combined with cloning technology, artificial wombs raise the prospect that gay couples could give 'birth' to their own children. 'This would no doubt horrify right-wingers, while the implications for abortion law might well please them,' he added.
Gelfand also warned that artificial wombs could have unexpected consequences for working women and health insurance. 'They would mean that women would no longer need maternity leave - which employers could become increasingly reluctant to give.
'It may also turn out that artificial wombs provide safer environments than natural wombs which can be invaded by drugs and alcohol from a mother's body. Health insurance companies could actually insist that women opt for the artificial way.
'Certainly, this is going to raise a lot of tricky problems.'