Sunday, August 31, 2008

Willingness to accept risk; patients vs. clinicians

A study in tomorrow's British Journal of Obstetrics and Gyaecology has been receiving a lot of press. Unfortunately, the study is grossly underpowered, poorly conducted, and the authors misinterpret their own results. The study is Vaginal delivery compared with elective caesarean section: the views of pregnant women and clinicians. The authors interviewed women expecting their first baby as well as a variety of clinicians (obstetricians, midwives, urogynecologists and colorectal surgeons). The authors claim to have found that patients and midwives were much more willing to tolerate risk of serious adverse outcomes than obstetricians, urogynecologists and colorectal surgeons.

The technical problems with the study are rather straightforward and call the validity of the results into question. There are very few participants in the study [Nulliparas (n = 122), midwives (n = 84), obstetricians (n = 166), urogynaecologists (n = 12) and colorectal surgeons (n = 79)], too few for any meaningful results. In addition, the recruitment process for pregnant women introduced bias into the sample; women who did not speak fluent English were barred from participating in the study, as were women who were obese, had underlying medical conditions, or pregnancy complications. Of 193 women who were approached for the study, 58 refused to participate and 30 additional women were subsequently excluded.

The authors introduced further bias providing their view of the complications of C-section:
A detailed explanation of caesarean section and its possible complications (major abdominal surgery, anaesthesia requirements, wound pain and need for more analgesia, decreased mobility, longer hospital stay, inability to drive for 6 weeks; increased risk of uterine, pelvic and bladder infection, wound breakdown, blood loss, transfusion, thrombosis; potential risks in future pregnancies, placenta accreta, uterine scar rupture; and neonatal respiratory problems with potential neonatal intensive care unit admission, jaundice, and temporary feeding difficulties)...
The authors do not reveal whether women were provided with information about the incidence of these complications, or merely told that they could occur.

The study participants were presented with a variety of complications of vaginal delivery, and asked to quantify the amount of risk they were willing to accept for each specific complication before they would abandon vaginal delivery in favor of elective C-section. Clinicians were asked the same questions, but were instructed to respond as if they or their partner were the pregnant patient. In virtually every category, both patients and midwives expressed a higher tolerance than obstetricians, urogynecologists and colorectal surgeons for accepting complications of vaginal delivery rather than choosing an elective C-section.

The authors offer this interpretation of their findings:
Our findings demonstrate that women are able to quantify the risks of VD they would be prepared to accept before they would request an elective caesarean section. Compared with clinicians, pregnant women tend to have a much higher threshold for the potential complications of VD, especially those associated with the pelvic floor. Anal incontinence was the potential complication with the lowest utility score for pregnant women. All groups ranked pelvic floor problems fourth of the top five reasons for preferring an elective caesarean section over VD. Pregnant women’s views more closely resembled those of midwives than those of other clinicians...

The caesarean section rate has risen in most developed countries over the past 10–15 years partially because of maternal request and lower thresholds among physicians
to perform the operation due to increasing levels of litigation. Florica et al. found an increase in caesarean section over a 5-year period to be due to suspected fetal distress, maternal request and labour dystocia. Our study demonstrates
that low-risk obstetric women are more accepting of many of the risks of VD than clinicians. However, when faced with the alternative choices of potential severe
complications either for themselves or for their baby from VD, many will preferentially choose delivery by caesarean section...

We have shown that both pregnant women and clinicians are able to quantify the different levels of potential risks (utility scores) they would be prepared to accept before requesting an elective caesarean section, while being aware of the potential complications of elective caesarean section.
Actually, they've shown nothing of the kind. First of all, the authors failed to include main complication that elective C-section is typically used to prevent: injury to the baby. They only looked at willingness to accept risk of specific maternal complications of vaginal delivery.

Secondly, and far more important, they showed that people with little or no experience of bad outcomes (women and midwives) were more willing to accept the risks of complications they had never seen than clinicians who were directly acquainted with those complications. That does not tell us anything about their tolerance of risk, it merely tells us about their understanding of risk.

This study reminds me of studies that compare teen driver and adult driver tolerance for risk during driving. According to studies like Hazard and Risk Perception among Young Novice Drivers:
Research indicates that young drivers underestimate the risk of an accident in a variety of hazardous situations. At the same time, they overestimate their own driving skill. Young drivers are also more willing to accept risk while driving than experienced drivers.
The willingness of teenagers to accept risk tells us nothing about their willingness to accept poor outcomes, it only tells us that they do not have a mature understanding of the risks.

Similarly, this study does NOT indicate that women are more willing to accept the complications of vaginal delivery than clinicians. It tells us that women do not have any basis for understanding the risks. Unless and until the authors can demonstrate that women and midwives who do have experience with the specific complications are willing to accept those complications, they've told us nothing.


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