The use of posthumous frozen sperm after cancer treatment is well-established, but success rates are low. Scientists say that a treatment, known as ICSI (intracytoplasmic sperm injection), in which sperm is injected directly into the egg, offers a far greater chance of a viable pregnancy in these cases.
The case, reported in the British Medical Journal, comes as Diane Blood, whose battle to have her dead husband's child has won widespread support of doctors and the public, announced she will take her case to the Court of Appeal on Monday.
Mrs Blood, 31, whose husband slipped into a coma and died of meningitis before giving written permission for his sperm to be used, is challenging a ruling by the Human Fertilisation and Embryology Authority (HFEA) - subsequently upheld by the High Court - not to let her have fertility treatment here or abroad.
Mrs Blood's father, Michael McMahon, yesterday said his daughter had been advised by lawyers that she had a good legal case. She will be claiming the rulings were unreasonable, and that her rights under European law superseded British legal restrictions.
She will also argue that when the sperm sample was taken from her husband he was still alive, and written consent should not have been necessary. Mr McMahon said: "She is very, very optimistic now, but at the same time she's terrified of losing at this stage. It means so much to her.
Doctors and scientists from London, Swansea, and Tyne and Wear, involved in the twin pregnancy in the 36-year-old woman whose husband died of testicular cancer, say that a comparison of this and the Blood case shows the "limitations" of the law as it stands.
They say that sperm collected from an unconscious man - which the HFEA permits - cannot ever used for treatment unless he recovers. Written consent is needed prior to use of the sperm in fertility treatments.
"As shown by our case, the HFEA is not opposed to post-humous assisted reproduction provided written consent is obtained. But death is seldom convenient," the doctors write.
"The comparison of the two cases shows the limitation of the current law; it is conveniently applicable in a chronic illness but not so in an acute illness. Such inflexibility is germane to neither the human condition nor a rapidly changing medical field."
In the same issue of the BMJ, Professor Sir Douglas Black, former chief scientist in the Department of Health between 1973-77, describes the decision to refuse Mrs Blood treatment, as "corporate tyranny."
He writes: "It seems to me that this is a case in which the distress and hardship to an individual are glaringly obvious and the value to society, still less to anyone person, minimal. That view presupposes that legal and ethical principles are contingent, and not absolutes that need to be defended at whatever cost to actual living people."