Why Cochrane Childbirth Reviews are often worse than useless


According to Peggy O’Mara, Editor of Mothering.com:

One source that does not have a conflict of interest is the Cochrane Collaboration, internationally recognized as the highest standard in evidence-based healthcare reviews. When Cochrane compared the midwifery model of care to other models of maternity care, they concluded “that most women should be offered midwife-led continuity models of care…” Cochrane also says that there is no strong evidence to favor either planned homebirth or hospital birth.

O’Mara is wrong.

O’Mara is not alone in her reliance on Cochrane Reviews. Lay people love Cochrane pregnancy and childbirth reviews. They always include easy to understand plain language summaries and are generally written by volunteers, many with an natural childbirth ax to grind.

To understand why Cochrane Reviews, particularly childbirth reviews, are often a poor standard of evidence, it helps to understand what Cochrane Reviews are and what they are not. Cochrane Reviews are systematic analysis of randomized controlled trials on a particular topic. Randomized controlled trials (RCTs) are trials in which two treatment options assigned randomly to two groups and in ideal cases neither the patient nor the scientist knows what treatment the patient received (double blind). RCTs are considered the “gold standard” in scientific research.

But what happens when RCTS are either unfeasible or unethical or both? For example, it is unethical to ignore women’s preferences and randomize them to home or hospital birth. Does that mean that it is impossible to investigate the relative safety of home and hospital birth? No, it does not. While RCT’s are at the top of the hierarchy of research methods, there are many forms of research including cohort studies, case-control studies and case series, among others.

But Cochrane Reviews do not consider these other forms of evidence, not because they are unreliable, but because they are outside the scope of Cochrane Reviews. That’s fine, but then they go ahead and do something that is not fine at all. When there are limited RCT’s or poor quality RCT’s, they analyze them anyway as if such an analysis could provide accurate data. Since it is unethical to perform an RCT on homebirth, there should be NO Cochrane Review of homebirth. Instead there is a review that is nothing more than garbage.

Here’s what the Cochrane Review of homebirth showed:

Main results

Two trials met the inclusion criteria but only one trial involving 11 women provided some outcome data and was included. The evidence from this trial was of moderate quality and too small to allow conclusions to be drawn. (my emphasis)

Authors’ conclusions

There is no strong evidence from randomised trials to favour either planned hospital birth or planned home birth for low-risk pregnant women.

No, there is no evidence PERIOD. Therefore no conclusion can be drawn PERIOD.

The bottom line is obvious. When it is unethical to perform RCTs or the RCT’s that exist are small and underpowered, a systematic review of RCTs is worthless. Hence the Cochrane Review of homebirth is useless.

Let me amend that: by publishing a “systematic review” that includes only 11 women, the Cochrane Childbirth Group makes it clear that they are willing to publish garbage if that is the alternative to publishing nothing at all.