Almost every day a scientific or medical development seems to bring new promise and controversy to mankind; none more so, perhaps, than in the field of human fertility.
A quarter of a century ago the first test-tube baby, Louise Brown, was born. Now scientists have raised another startling prospect - "unborn mothers".
The notion that children can derive from human matter that has not itself been born sounds the stuff of science fiction. Yet it has moved a step closer with research showing that it is possible to extract ovarian tissue from aborted foetuses for in-vitro fertilisation (IVF) treatment.
Scientists announced yesterday that they have been able to remove immature ovaries from four-month-old foetuses. The theory is that they can then be stimulated in the test tube to go through the later stages of development before the creation of fully mature eggs.
But such a scenario raises grave ethical questions about the possibility of creating children whose biological mothers were never born. When a high-powered committee of British ethicists considered this possibility in the early 1990s it took the view that any child created by such a procedure would not be able to come to terms with the idea of deriving from aborted foetal tissue.
However, it is clear that the increase in demand for a supply of healthy human eggs - which are not easy to "harvest" from even the most fertile women - is causing several groups of scientists around the world to explore the possibility of using aborted foetuses.
Medical researchers from Israel and the Netherlands have now gone further than any previous attempt at experimenting with ovarian tissue from human foetuses. They artificially stimulate fluid-filled sacs or follicles within surgically removed ovaries to undergo several stages of development.
Normally an egg develops within the follicle as it goes through four developmental phases - the primordial, primary, secondary and pre- ovulatory stages - before it is released from the ovary into the Fallopian tubes.
The scientists said they had managed to culture foetal ovaries in test tubes to enter the start of the secondary stage. This is when the ovarian follicles begin to produce the female sex hormones necessary to develop and mature the eggs.
Tal Biron-Shental, a gynaecologist from Meir Hospital-Sapir Medical Centre in Kfar Saba, released the findings of the study at the annual meeting of the European Society for Human Reproduction and Embryology in Madrid.
Dr Biron-Shental said that the researchers obtained ovarian tissue from seven aborted foetuses aged between 22 and 33 weeks and managed to keep slices of the ovaries alive for four weeks, long enough for the follicles to develop to the stage when they began to produce the female hormone oestradiol.
"We didn't have mature oocytes, we had follicles that changed from primordial follicles and survived. We had E2 [oestradiol] secretion which means that we had more secondary follicles which means there was a development," Dr Biron-Shental said.
"This is the first report showing survival of second and third trimester human foetal ovarian follicles in culture with E2 production. E2 was probably secreted from the few secondary follicles in the cultured slices," she told the meeting.
The study in Israel was run with the veterinary department of Utrecht University, which supplied some of the culture medium for the test-tube development of the ovarian tissue. Full ethical approval was obtained prior to the study being carried out, the scientists confirmed.
"The local ethical committee of our medical centre approved the study and informed consent was obtained from the mothers," Dr Biron-Shental said. "We had different kinds of aborted foetuses with all kinds of malformations. Of course we could not use normal foetuses for such experiments because it is controversial enough," she explained.
However, there was one exception. "We had one aborted foetus that was completely normal and the abortion took place because the mother of the foetus had severe psychiatric problems. There are a lot of ethical questions on this point. Since it is still preliminary results we don't have all the answers for those ethical questions," she added.
Asked how long it would be before she was able to produce fully mature eggs from foetal ovaries, Dr Biron-Shental said: "It will still take a long time. I don't know exactly.
"We have an end goal and we continue to culture follicles from aborted foetuses. We have tried to improve the culture media and to prolong the culture period. We hope to get better results and more follicles," she said. "I am fully aware of the controversy about this, but probably, in some places, it will be ethically acceptable."
Anti-abortion groups were quick to denounce the research yesterday. Nuala Scarisbrick of the organisation Life said the study was morally repugnant. "Who would want to know that their mother was an aborted baby?" she said.
Françoise Shenfield, an ethicist at University College London and a former member of the Human Fertilisation and Embryology Authority, also voiced concerns about where this sort of research was leading.
"I would be very troubled by this not only for ethical reasons but for psychological reasons, because what is the public going to think about where the eggs come from?" Dr Shenfield said.
A spokeswoman for the HFEA said that the use of ovarian tissue from foetuses was considered by a committee of ethicists in 1994, which led the authority to decide that it would be difficult for a child to come to terms with the idea that it had been created from aborted foetal material because of prevailing social attitudes.
"The authority does not consider the use of tissue from this source to be acceptable for infertility treatment. But the authority does allow the use of foetal material to produce eggs for research provided that it is taken only with full, explicit consent," she said.
Roger Gosden, a leading fertility specialist working at the Jones Institute in Norfolk, Virginia, said the ethical issues centre on the issue of informed consent - the foetus cannot give its consent.
Dr Gosden also questioned whether the research was necessary because he had demonstrated that it is possible to obtain ovarian tissue from adult women with the aim of culturing the follicles in vitro to produce mature eggs.
"I would say that we don't need to use foetal material. The only advantage in doing so is that there are a huge number of eggs there, but obviously we have to be very sensitive to ethical issues," he said.
"We should be able to study foetal ovaries for research purposes, but it's the application in reproduction that I have concerns about," he added.
Experiments with mice have shown that it is possible to mature foetal eggs fully, fertilise them in a test tube, implant them into an adult mouse and produce healthy offspring. Some scientists hope to be able to do the same with human material.