That's when the question of whether the treatment was negligent arises. The Supreme Court has recently issued a judgement (Montgomery v Lanarkshire Health Board  UK SC11) which has resulted in a significant shift in how medical negligence cases are going to be dealt with in future and might result in more successful claims.
There are two things to consider when thinking about medical negligence . The first is whether or not the treatment itself was carried out properly , and the second is were the risks properly explained , so that the patient gave 'informed consent' to the treatment.
Judges apply a particular test to see whether a doctor has been negligent . They ask themselves three questions :
(1) Is there a standard practice for the treatment ?
(2) Did the doctor follow that practice?
(3) If not, was the treatment carried out one that no reasonably competent doctor would have done?
When treatment goes wrong, that's often a difficult test for someone pursuing a claim to meet.
The second thing to think about is whether or not the risks of the proposed treatment were properly explained. If they were not and the patient can convince a judge they wouldn't have had the treatment that went wrong , if they had known the risks, then there might be a claim. That's known as informed consent.
That's the situation Mrs Montgomery found herself in. She was small, diabetic and pregnant. She was expecting a larger than average baby - a known side effect of diabetes. She was being treated as a high risk pregnancy. However, she was not told of the risk to her and her baby that the baby might become stuck during labour, nor was the possibility of a Caesarean discussed with her. Mrs Montgomery's baby did become stuck, was starved of oxygen as a result and was born severely disabled.
The doctor treating her regarded the risk of grave consequences to the baby arising from having become stuck, as too low to mention - even though the chances of becoming stuck were quite high - at around 10%. She also didn't mention having a Caesarean, because, she said, every diabetic woman, knowing that their baby might become stuck, would want one - which wasn't in their maternal interests, as decided by the doctor.
The judge who first heard the case applied the three stage test to decide if there was a claim. He decided that , in not mentioning the risks, the doctor was following the standard practice at the time and , accordingly , she wasn't negligent. The Appeal Court in Edinburgh agreed.
However, the case was appealed to the Supreme Court in London and they decided when dealing with explaining risks, that that was the wrong way to look at it. Instead, they decided that:
'The doctor is …under a duty to take reasonable care to ensure that the patient is aware of any material risks involved in any recommended treatment, and of any reasonable alternative or variant treatments. The test of materiality is whether, in the circumstances of the particular case, a reasonable person in the patient’s position would be likely to attach significance to the risk, or the doctor is or should reasonably be aware that the particular patient would be likely to attach significance to it.'
That puts the patient, rather than the doctor, at the heart of the decision making process. The Supreme Court decided Mrs Montgomery should have been told the risks and about the possibility of a Caesarean . They decided that had she been told, she'd have opted for the operation and her child would have been delivered safely and unharmed.
The test set out in this case reflects modern medical practice , so we may not see a huge increase in cases. However, it's clear guidance to the medical profession and to lawyers when dealing with these cases and is very welcome.