By Martin Hutchinson
BBC News Online health staff in Madrid
A drug which may encourage embryos to implant in the womb has shown encouraging results in early trials - producing babies for women who had endured repeated IVF failures.
Vicenza and Andrew Walls enrolled in the trial
The drug, LIF, will now move to wider trials before it is offered routinely to women.
Fertility treatment is successful in fewer than half of all couples who try them, even after repeated attempts.
Many of these failures cannot be properly explained, although doctors suspect that in some cases, the fertilised embryo fails to implant correctly in the wall of the womb after it is transferred back by doctors.
A trial at two UK clinics is examining a new drug, LIF, which is made up of a body chemical thought to play a vital role in the "latching on" of the embryo to the surface of the womb.
It is normally secreted by the lining of the womb itself during the time of a woman's fertile cycle in which a fertilised embryo is most likely to be passing by.
A total of 40 women were given LIF, and another 20 a placebo drug.
Nine healthy babies were born to mothers who had taken LIF - all of whom had gone through at least three, and up to seven, previous unsuccessful IVF treatments.
Of course, the was always a glimmer of hope that our dream would come true
Vicenza Walls, trial participant
Results of the trial were announced at the European Society of Human Reproduction and Embryology Annual Meeting in Madrid.
One couple involved in the trial at Bourn Hall Clinic in Cambridgeshire, Vicenza and Andrew Walls, had their first child Emily - now almost a year old - after seven days of LIF injections at the critical moment in her cycle.
Vincenza, 38, said she and her husband had been resigned to not having children until they heard about the trial.
She said: "We didn't know at the time if we would be given the drug or a placebo, but we thought if it could ultimately help other couples in our situation, it was worth giving it a go.
Their daughter Emily is nearly one year old
"Of course, the was always a glimmer of hope that our dream would come true.
"Emily has brought so much joy into our lives - she's our miracle.
"I think because of all we went through, every time we look at her, we appreciate her being here."
Dr Peter Brinsden, Bourn Hall's medical director, said that more women were now needed to launch bigger trials of the drug.
"We are looking for women aged under 38 who have previously been unsuccessful with two or more IVF treatments, to take part in this new trial."