AS science advances with increasing speed, medical ethical issues become ever more complex.

Yesterday, the European Court of Human Rights ruled against Natallie Evans, effectively denying her the chance to have her own, genetic child.

Before being left infertile by ovarian cancer, Ms Evans had IVF treatment with her partner Howard Johnston which created six embryos. Then the couple split up, and now Mr Johnston is refusing to allow Ms Evans permission to use the frozen embryos.

We have enormous sympathy for both parties and, indeed, the judges.

So complex is this case that Ms Evans appears to be a little bit pregnant. In the old days, you either were pregnant, or you were not. Ms Evans is a little bit pregnant because she has embryos that could grow into a child - it is just that they are not inside her.

Putting aside the reproductive ethics that the judges considered, there is an old-fashioned human value that might have some bearing upon this case: constancy.

The couple had a gentleman's agreement. She provided the eggs, he provided the sperm, and together they were going to have a child.

If Ms Evans had been properly pregnant when they split up, Mr Johnston would not have been able to terminate their child. If the child had been born when they split up, Mr Johnston would not have been able to kill it.

So how come when she's a little bit pregnant is he able to prevent it growing, and prevent her from ever having her own baby? That's what he agreed to back when he agreed to create the embryo; it is only his volte face that has created the ethical dilemma that the judges are considering.

Surely, because of the special nature of the circumstances, a legal form of words could have prevented Mr Johnston from becoming financially liable for the child.

Or does this very human response to a woman who desperately wants her only chance to have her own baby betray its navet and stumble into too dangerous an ethical minefield?