MacDorman studies further undermined by new dataHomebirth and "natural" childbirth advocates like to claim that Cesarean section increases the risk of neonatal death almost 3 fold, based on the findings of Marian MacDorman and colleagues. What they do not realize is that MacDorman herself has already revised this claim drastically downwards, and that even then, the conclusions are false.
In September 2006, MacDorman et al. published (and heavily publicized with interviews to the lay press) a paper that purported to show that Cesarean section increases the risk of neonatal death almost 3 fold. MacDorman et al. compared outcomes of C-sections with "no indicated risk" (a blank space on the risk section of the birth certificate) with outcomes from vaginal deliveries with "no indicated risk" and found that the neonatal death rate was higher in the C-section group. However, MacDorman neglected to mention that it is well known that the risk section of the birth certificate is often left blank even when there are serious risk factors and complications. Indeed, in 50% or more of serious risk factors (heart disease, kidney disease, etc.) the space is left blank. So their assumption that "no indicated risk" means no risk is completely unjustified.
In the follow up paper Neonatal Mortality for Primary Cesarean and Vaginal Births to Low-Risk Women: Application of an "Intention-to-Treat" Model, MacDorman et al. use the same dataset, known to be flawed and incomplete, but applied a better form of analysis. Using this new, more accurate statistical analysis, MacDorman et al. went back and reviewed their incomplete, flawed dataset.
...In the most conservative model, the adjusted odds ratio for neonatal mortality was 1.6 (95% CI 1.35–2.11) for cesareans with no labor complications or procedures, compared with planned vaginal deliveries. Conclusions: The finding that cesarean deliveries with no labor complications or procedures remained at a 69 percent higher risk of neonatal mortality than planned vaginal deliveries is important, given the rapid increase in the number of primary cesarean deliveries without a reported medical indication.MacDorman et al. adjusted their claim downward by a substantially amount. Instead of their original claim that C-section increases the risk of neonatal death by 200%, they now find that C-section increases the rate of neonatal death by only 69%. Yet even then, they failed to acknowledge the most significant flaw in the paper. MacDorman and colleagues assumed that a birth certificate that listed no risk factors for C-section indicated that there really were no risk factors. A large body of data on the accuracy of birth certificates had long ago shown that more than 50% of cases of major risk factors were never listed on the birth certificate and that, therefore, their assumption was completely unjustified.
In the January issue of Obstetrics and Gynecology there is a new paper that adds to the mountain of evidence demonstrating that it is impossible to determine C-section risk factors merely by looking at birth certificates. According to Cesarean Delivery Among Women With Low-Risk Pregnancies: A Comparison of Birth Certificates and Hospital Discharge Data:
Among 40,932 women with primary cesarean deliveries and no risk indicated on the birth certificate, 35,761 (87.4%) had a risk identified in the hospital discharge data. The overall agreement between data sources on the presence of any risk indicator was low (κ=0.18). Among primary cesarean deliveries, the percentage without indicated risk was 58.3% when using birth certificate data alone and 3.9% when using hospital discharge data in combination with the birth certificate.In other words, virtually all women who had primary C-sections but had no risk factors on the birth certificate, actually did have risk factors. In the case of the MacDorman study, the authors reported that there were 469 deaths out of 271,179 births to women who had primary C-sections and no risks documented on the birth certificate. Yet if 87% of the birth certificates were inaccurate, that means that over 235,000 were wrongly placed in this category, thoroughly invalidating the results of the study.
CONCLUSION: Using birth certificate information alone overestimated the proportion of women who had no-indicated-risk cesarean deliveries in Georgia. Evidence of many indications for cesarean delivery can be found only in the hospital discharge data. The construct of no indicated risk as determined from birth certificates should be interpreted with caution, and the use of linked data should be considered whenever possible.
The bottom line is that there is no evidence that C-section increases the risk of neonatal death in this study or in any other study to date.