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Hilary Term[2015] UKSC 11On appeal from: [2013] CSIH 3; [2010] CSIH 104JUDGMENTMontgomery (Appellant) v Lanarkshire HealthBoard (Respondent) (Scotland)beforeLord Neuberger, PresidentLady Hale, Deputy PresidentLord KerrLord ClarkeLord WilsonLord ReedLord HodgeJUDGMENT GIVEN ON11 March 2015Heard on 22 and 23 July 2014

AppellantJames Badenoch QCColin J MacAulay QCLauren Sutherland(Instructed byBalfour Manson LLP)RespondentRory Anderson QCNeil R Mackenzie(Instructed by NHSNational Services ScotlandCentral Legal Office)Intervener (GeneralMedical Council)Andrew Smith QC(Instructed by GMCLegal)

LORD KERR AND LORD REED: (with whom Lord Neuberger, LordClarke, Lord Wilson and Lord Hodge agree)Introduction1.Nadine Montgomery gave birth to a baby boy on 1 October 1999 at BellshillMaternity Hospital, Lanarkshire. As a result of complications during thedelivery, the baby was born with severe disabilities. In these proceedings MrsMontgomery seeks damages on behalf of her son for the injuries which hesustained. She attributes those injuries to negligence on the part of Dr DinaMcLellan, a consultant obstetrician and gynaecologist employed byLanarkshire Health Board, who was responsible for Mrs Montgomery’s careduring her pregnancy and labour. She also delivered the baby.2.Before the Court of Session, two distinct grounds of negligence wereadvanced on behalf of Mrs Montgomery. The first concerned her ante-natalcare. It was contended that she ought to have been given advice about the riskof shoulder dystocia (the inability of the baby’s shoulders to pass through thepelvis) which would be involved in vaginal birth, and of the alternativepossibility of delivery by elective caesarean section. The second branch ofthe case concerned the management of labour. It was contended that DrMcLellan had negligently failed to perform a caesarean section in responseto abnormalities indicated by cardiotocograph (“CTG”) traces.3.The Lord Ordinary, Lord Bannatyne, rejected both grounds of fault: [2010]CSOH 104. In relation to the first ground, he based his decision primarily onexpert evidence of medical practice, following the approach laid down by themajority in Sidaway v Board of Governors of the Bethlem Royal Hospital andthe Maudsley Hospital [1985] AC 871. He also concluded that, even if MrsMontgomery had been given advice about the risk of serious harm to her babyas a consequence of shoulder dystocia, it would have made no difference inany event, since she would not have elected to have her baby delivered bycaesarean section. That decision was upheld by the Inner House (Lord Eassie,Lord Hardie and Lord Emslie): [2013] CSIH 3; 2013 SC 245.4.The appeal to this court has focused on the first ground of fault. The courthas been invited to depart from the decision of the House of Lords in Sidawayand to re-consider the duty of a doctor towards a patient in relation to adviceabout treatment. The court has also been invited to reverse the findings of theLord Ordinary in relation to causation, either on the basis that his treatmentPage 2

of the evidence was plainly wrong, or on the basis that, instead of applying aconventional test of “but for” causation, he should instead have applied theapproach adopted in the case of Chester v Afshar [2004] UKHL 41; [2005] 1AC 134.5.Before considering those issues, we shall explain in greater detail the relevantfacts and the approach adopted by the courts below.The facts6.Mrs Montgomery studied molecular biology at Glasgow University andgraduated with a BSc. She then worked for a pharmaceutical company as ahospital specialist. She was described by the Lord Ordinary as “a clearlyhighly intelligent person”. Her mother and sister are both general medicalpractitioners.7.In 1999 Mrs Montgomery was expecting her first baby. She is of smallstature, being just over five feet in height. She suffers from insulin dependentdiabetes mellitus. Women suffering from diabetes are likely to have babiesthat are larger than normal, and there can be a particular concentration ofweight on the babies’ shoulders. Because of her diabetes, Mrs Montgomery’swas regarded as a high risk pregnancy requiring intensive monitoring. Shetherefore attended the combined obstetric and diabetic clinic at BellshillMaternity Hospital, under the care of Dr McLellan, throughout herpregnancy.8.The widest part of a baby’s body is usually the head. If the head successfullydescends through the birth canal, in a normal birth the rest of the body willdescend uneventfully. Since the widest part of the body of a baby whosemother is diabetic may be the shoulders the head may descend but theshoulders can be too wide to pass through the mother’s pelvis withoutmedical intervention. This phenomenon, known as shoulder dystocia, is theprime concern in diabetic pregnancies which proceed to labour. It wasdescribed by Dr Philip Owen, an expert witness who gave evidence on behalfof the Board, as “a major obstetric emergency associated with a short andlong term neonatal and maternal morbidity [and] an associated neonatalmortality”.9.That evidence is consistent with guidance issued by the Royal College ofObstetricians and Gynaecologists, which states that there can be a highperinatal mortality and morbidity associated with the condition, even when itPage 3

is managed appropriately. Maternal morbidity is also increased: in 11% ofcases of shoulder dystocia there is postpartum haemorrhage, and in 3.8%fourth degree perineal tears. The guidance advises that help should besummoned immediately when shoulder dystocia occurs. When the mother isin hospital this should include assistance from midwives, an obstetrician, apaediatric resuscitation team and an anaesthetist.10.According to the evidence in this case, about 70% of cases of shoulderdystocia can be resolved by what is known as a “McRoberts’” manoeuvre.This involves two midwives or nurses taking hold of the mother’s legs andforcing her knees up towards her shoulders, so as to widen the pelvic inlet bymeans of hyperflexion. An attempt can also be made to manoeuvre the babyby suprapubic pressure. This procedure involves the doctor making a fist withboth hands and applying pressure above the mother’s pubis, in order todislodge the baby’s shoulder and push the baby down into the pelvis. Anotherprocedure which may be attempted is a “Zavanelli” manoeuvre. This involvespushing the baby’s head back into the birth canal, to the uterus, so as to beable to perform an emergency caesarean section. Another possible procedureis a symphysiotomy. This is a surgical procedure which involves cuttingthrough the pubic symphysis (the joint uniting the pubic bones), so as to allowthe two halves of the pelvis to be separated.11.According to Dr McLellan’s evidence, in some cases the mother may beentirely unaware that shoulder dystocia has occurred. It is clear, however,that when shoulder dystocia happens and the mother knows of it, dealing withit is, at least, an unpleasant and frightening experience for her. It also givesrise to a variety of risks to her health.12.Shoulder dystocia also presents risks to the baby. The physical manoeuvresand manipulations required to free the baby can cause it to suffer a brokenshoulder or an avulsion of the brachial plexus – the nerve roots which connectthe baby’s arm to the spinal cord. An injury of the latter type may be transientor it may, as in the present case, result in permanent disability, leaving thechild with a useless arm. The risk of a brachial plexus injury, in cases ofshoulder dystocia involving diabetic mothers, is about 0.2%. In a very smallpercentage of cases of shoulder dystocia, the umbilical cord becomes trappedagainst the mother’s pelvis. If, in consequence, the cord becomes occluded,this can cause the baby to suffer from prolonged hypoxia, resulting in cerebralpalsy or death. The risk of this happening is less than 0.1%.13.Mrs Montgomery was told that she was having a larger than usual baby. Butshe was not told about the risks of her experiencing mechanical problemsduring labour. In particular she was not told about the risk of shoulderPage 4

dystocia. It is agreed that that risk was 9-10% in the case of diabetic mothers.Unsurprisingly, Dr McLellan accepted that this was a high risk. But, despitethe risk, she said that her practice was not to spend a lot of time, or indeedany time at all, discussing potential risks of shoulder dystocia. She explainedthat this was because, in her estimation, the risk of a grave problem for thebaby resulting from shoulder dystocia was very small. She considered,therefore, that if the condition was mentioned, “most women will actuallysay, ‘I’d rather have a caesarean section’”. She went on to say that “if youwere to mention shoulder dystocia to every [diabetic] patient, if you were tomention to any mother who faces labour that there is a very small risk of thebaby dying in labour, then everyone would ask for a caesarean section, andit’s not in the maternal interests for women to have caesarean sections”.14.During her fortnightly attendances at the clinic, Mrs Montgomery underwentultrasound examinations to assess foetal size and growth. The finalultrasound examination was on 15 September 1999, at 36 weeks gestation.Dr McLellan decided that Mrs Montgomery should not have a furtherultrasound examination at 38 weeks, because she felt that Mrs Montgomerywas becoming anxious as a result of the information revealed by the scansabout the size of her baby. That sense of anxiety related to her ability todeliver the baby vaginally.15.Based on the 36 weeks ultrasound, Dr McLellan estimated that the foetalweight at birth would be 3.9 kilograms. She made that estimate on theassumption that the baby would be born at 38 weeks. This is importantbecause Dr McLellan gave evidence that, if she had thought that the baby’sweight was likely to be greater than 4 kilograms, she would have offered MrsMontgomery a caesarean section. In keeping with general practice DrMcLellan would customarily offer a caesarean section to diabetic motherswhere the estimated birth weight is 4.5 kilograms. She decided to reduce thatthreshold to 4 kilograms in Mrs Montgomery’s case because of her smallstature.16.As Dr McLellan was aware, estimating birth weight by ultrasound has amargin of error of plus or minus 10%. But she decided to leave this out ofaccount, stating that “if you do that you would be sectioning virtually alldiabetics”. By the time of the 36-week examination, Dr McLellan had alreadymade arrangements for Mrs Montgomery’s labour to be induced at 38 weeksand 5 days. She accepted in evidence that she should have estimated thebaby’s birth weight as at 38 weeks and 5 days, rather than 38 weeks, and thatthe estimated birth weight would then have been over 4 kilograms which was,of course, beyond the threshold that she herself had set. In the event, the babywas born on the planned date and weighed 4.25 kilograms.Page 5

17.At the 36-week appointment, Dr McLellan noted that Mrs Montgomery was“worried about [the] size of [the] baby”. In her evidence, she accepted thatMrs Montgomery had expressed concern at that appointment about the sizeof the foetus and about the risk that the baby might be too big to be deliveredvaginally. Dr McLellan also accepted that it was possible that MrsMontgomery had expressed similar concerns previously. Certainly, she said,such concerns had been mentioned more than once. She stated that MrsMontgomery had not asked her “specifically about exact risks”. Had MrsMontgomery done so, Dr McLellan said that she would have advised herabout the risk of shoulder dystocia, and also about the risk of cephalopelvicdisproportion (the baby’s head becoming stuck). In the absence of suchspecific questioning, Dr McLellan had not mentioned the risk of shoulderdystocia, because, as we have already observed, it was her view that the riskof serious injury to the baby was very slight. In accordance with her practicein cases where she felt (in her words) that it was “fair to allow somebody todeliver vaginally”, Dr McLellan advised Mrs Montgomery that she would beable to deliver vaginally, and that if difficulties were encountered duringlabour then recourse would be had to a caesarean section. Mrs Montgomeryaccepted that advice. But if she had requested an elective caesarean section,she would have been given one.18.Mrs Montgomery said in evidence that if she had been told of the risk ofshoulder dystocia, she would have wanted Dr McLellan to explain to her whatit meant and what the possible risks of the outcomes could be. If she hadconsidered that it was a significant risk to her (and, in light of what she hadsubsequently learned, she would have assessed it as such) she would haveasked the doctor to perform a caesarean section.19.As we have explained, Dr McLellan gave evidence that diabetic patients whohad been advised of the risk of shoulder dystocia would invariably choosethe alternative of delivery by caesarean section. She also gave evidence thatMrs Montgomery in particular would have made such an election:“since I felt the risk of her baby having a significant enoughshoulder dystocia to cause even a nerve palsy or severe hypoxicdamage to the baby was low I didn’t raise it with her, and hadI raised it with her then yes, she would have no doubt requesteda caesarean section, as would any diabetic today.”20.Mrs Montgomery’s labour was induced by the administration of hormones,as Dr McLellan had planned. After several hours, labour became arrested.The strength of the contractions was then augmented by the administrationof further hormones over a further period of several hours, so as to overcomePage 6

whatever was delaying progress towards vaginal delivery. When the baby’shead nevertheless failed to descend naturally, Dr McLellan used forceps. At5.45 pm the baby’s shoulder became impacted at a point when half of hishead was outside the perineum.21.Dr McLellan had never dealt with that situation b