A young mother in the early stages of pregnancy suffers a fatal accident and is declared brain-dead at hospital. Devastated, her husband and family prepare to bury their loved one. Marlise Munoz, who collapsed at home with a blood clot in November, however, is yet to be buried: the Texas hospital where she was taken elected to keep her alive, they say, because state law forbids them cutting off life support. Is this a perversion of law, or the kind of case for which such rules are intended?

The story has ignited debate about the value of living wills in the US, an issue which gained a lot of attention circa Terry Schiavo but not much since. The assumption many have assumed to be that you, as a patient, should and do have the final say over whether life-extending measures would be taken in extreme circumstances and that your health directives will be respected. What many American women are now worrying about - thanks to the Munoz case - is that not if you're a woman, they don't.

Twelve US states have rules overturning any heath directives from comatose or vegetative state patients, including living wills, if the patient happens to be pregnant. Another 17 states have more vague instructions, with some exceptions dependent on viability of the foetus, possible harm caused by the treatment, or both. Only Wisconsin, Vermont, Oklahoma, Maryland, and New Jersey explicitly guarantee that a woman's advance directives would be upheld regardless of pregnancy.

However, far more surprising, are the number of states which don't have rules either way at all. A whopping 15 states plus Washington D.C. lack any statutory language regarding whether advance directives would be honoured in case of pregnancy. Given the advance both of life-saving or life-sustaining treatments, and immense pressure from the pro-life movement throughout the US, this seems an odd oversight.

Fights over the pregnancies of comatose women are hardly new, and the stories attending both sides' arguments are equally emotionally compelling.

In 1988 Nancy Klein, from New York, was left comatose after a car accident. She was two months' pregnant at the time with a wanted second child. Doctors put her chance of recovery at less than five per cent, and recommended terminating the pregnancy to give her better odds. Her husband and family agreed, but two abortion activists tried to apply for guardianship of the foetus to prevent the family's choice and act against the best advice of doctors.

Nancy Klein eventually came out of the coma and suffered some brain damage, eventually returning to work as an artist and designer. A result that, had the legal challenges been taken seriously, might never have happened. (The Kleins later divorced, after their story was dramatised for television in a special starring Henry Winkler.) In spite of this case, New York is one of the states with no specific wording to guide any future families like Nancy's faced with this difficult decision.

Around the same time the case of Barbara Blodgett also gained headlines. Also in coma, Blodgett resided in Washington, a state where a living will (had she had one) would have been ignored in favour of her pregnancy. She was three months into her pregnancy when she was hit by a drunk driver; she later gave birth while still comatose, then eventually made a recovery. A miracle no doubt: even more starkly underlined by the fact that at the time Blodgett's son was born, doctors knew of only five previous cases where mothers who fell into a coma while already pregnant had given birth to healthy children.

The crucial issue in Texas is whether the law applies to patients who are brain dead, not just in a coma or vegetative state. A Texas law passed in 1989 states “life-sustaining treatment” may not be withdrawn from a pregnant patient. But if someone is technically dead, what is the meaning of 'life-sustaining'? Brain death is the ceasing of all neurological activity, even if other functions can be artificially maintained.

When Munoz's family were told she was brain dead they made arrangements to honour her wish not to be kept on life support; the hospital, meanwhile, claims its actions - extending some biological function in someone who they have acknowledged will never live for the sake of seeing whether the pregnancy could be viable when it reaches 22 weeks' gestation - are following the letter of the law.

“All she is, is a host for a foetus,” said Mrs. Munoz’s father, Ernest Machado. “I get angry with the state. What business did they have delving into these areas? Why are they practicing medicine up in Austin [the state capital]?”

“The Texas Legislature can’t require doctors to do the impossible and try to treat someone who’s dead,” said Arthur L. Caplan, director of medical ethics at NYU Langone Medical Center to the New York Times. “I don’t think they intended this statute the way the hospital is interpreting it.”