The study of C-sections is afflicted with white hat bias.
What is white hat bias?
‘White hat bias’ [is] bias leading to distortion of information in the service of what may be perceived to be righteous ends… WHB bias may be conjectured to be fuelled by feelings of righteous zeal, indignation toward certain aspects of industry, or other factors. Readers should beware of WHB and … should seek methods to minimize it.
I’ve written about white hat bias before in relation to breastfeeding. In 2015 everyone “knows” that breast is best. Breastfeeding researchers are so sure that breastfeeding is beneficial that they exaggerate findings that place breastfeeding in a positive light.
[pullquote align=”right” color=””]It seems irresponsible to draw any conclusions from this data.[/pullquote]
Similarly, in 2015, everyone “knows” that the C-section rate is too high. Researchers are so sure that C-sections are harmful that they exaggerate findings that place C-sections in a negative light. A new paper about C-sections and asthma is a case in point.
According to yesterday’s New York Times:
For years, research has shown that babies born by cesarean section are more likely to develop health problems. Now, a groundbreaking study suggests that not all C-sections are equally risky…
Surprisingly, the data seemed to show more health problems among babies born by planned C-section than among those delivered by emergency C-section or vaginal birth, even though the planned surgery is done under more controlled conditions. The finding suggests that the arduous experience of labor — that exhausting, sweaty, utterly unpredictable yet often strangely exhilarating process — may give children a healthy start, even when it’s interrupted by a surgical birth.
Actually, the data on health problems caused by C-sections is weak and conflicting and this new study is more of the same.
The paper is Planned Cesarean Delivery at Term and Adverse Outcomes in Childhood Health by Akinbami et al. According to the authors:
Among offspring of women with first births in Scotland between 1993 and 2007, planned cesarean delivery compared with vaginal delivery (but not compared with unscheduled cesarean delivery) was associated with a small absolute increased risk of asthma requiring hospital admission, salbutamol inhaler prescription at age 5 years, and all-cause death by age 21 years. Further investigation is needed to understand whether the observed associations are causal.
What exactly did they find?
Compared with offspring born by unscheduled cesarean delivery (n = 56 015 [17.4%]), those born by planned cesarean delivery (12 355 [3.8%]) were at no significantly different risk of asthma requiring hospital admission, salbutamol inhaler prescription at age 5 years, obesity at age 5 years, inflammatory bowel disease, cancer, or death but were at increased risk of type 1 diabetes (0.66% vs 0.44%; difference, 0.22% [95% CI, 0.13%-0.31%]; adjusted hazard ratio [HR], 1.35 [95% CI, 1.05-1.75]). In comparison with children born vaginally (n = 252 917 [78.7%]), offspring born by planned cesarean delivery were at increased risk of asthma requiring hospital admission (3.73% vs 3.41%; difference, 0.32% [95% CI, 0.21%-0.42%]; adjusted HR, 1.22 [95% CI, 1.11-1.34]), salbutamol inhaler prescription at age 5 years (10.34% vs 9.62%; difference, 0.72% [95% CI, 0.36%-1.07%]; adjusted HR, 1.13 [95% CI, 1.01-1.26]), and death (0.40% vs 0.32%; difference, 0.08% [95% CI, 0.02%-1.00%]; adjusted HR, 1.41 [95% CI, 1.05-1.90]), whereas there were no significant differences in risk of obesity at age 5 years, inflammatory bowel disease, type 1 diabetes, or cancer.
Children born by planned C-section were at slightly increased risk of asthma requiring hospital admission, slightly increased risk of needing asthma medication at age 5 and increased risk of death both before age 1 and from 1-21. There were no significant differences in rates of obesity, inflammatory bowel disease, type I diabetes or cancer.
Comparing the effects of planned C-section to unplanned C-section revealed no difference in rates of asthma requiring hospital admission, need for asthma medication at age 5, obesity, inflammatory bowel disease, cancer or death, but an increased risk of type 1 diabetes.
So C-section appeared to slightly increase the risk of asthma (an auto-immune disease), but no other auto-immune diseases, and to increase the risk of unexplained death.
The authors also performed a sensitivity analysis. What is a sensitivity analysis?
The credibility or interpretation of the results of clinical trials relies on the validity of the methods of analysis or models used and their corresponding assumptions…
A sensitivity analysis addresses the validity of the assumptions used in calculating the results.
If, after performing sensitivity analyses the findings are consistent with those from the primary analysis and would lead to similar conclusions about treatment effect, the researcher is reassured that the underlying factor(s) had little or no influence or impact on the primary conclusions. In this situation, the results or the conclusions are said to be “robust”.
What was the result of the sensitivity analysis in this paper:
Complete case analyses comparing outcomes following planned cesarean delivery with unscheduled cesarean delivery demonstrated no significant differences in risk of any outcomes studied, as reported in Table 4. Complete-cases analysis revealed a significantly increased risk of offspring obesity at age 5 years following planned cesarean delivery compared with vaginal birth, but no significant differences in risk of salbutamol inhaler prescription at age 5 years, asthma requiring hospital admission, inflammatory bowel disease, cancer, or death up to age 21 years.
So, if I understand the sensitivity analysis correctly, it produced different results from the primary analysis, which means that the findings are NOT robust.
Nonetheless, the authors conclude:
Among offspring of women with first births in Scotland between 1993 and 2007, planned cesarean delivery compared with vaginal delivery (but not compared with unscheduled cesarean delivery) was associated with a small absolute increased risk of asthma requiring hospital admission, salbutamol inhaler prescription at age 5 years, and all-cause death by age 21 years. Further investigation is needed to understand whether the observed associations are causal.
It would have been more accurate to say that WEAK DATA showed a small absolute increase in the risk of asthma and unexplained death.
In other words, it seems rather irresponsible to draw any conclusions from this data. That didn’t stop the authors, though. They “know” that C-sections are bad and white hat bias led them to search until they found some weak data that seemed to support that pre-existing belief.
It’s yet another poor contribution to the confusing and conflicting papers that claim to show the “harms” of C-section, but, in truth, don’t show anything at all.
