Sunday, October 12, 2008

New Cochrane study promptly misinterpreted by midwifery advocates

A new study was published by the Cochrane Review this week, and midwifery advocates wasted no time in misunderstanding the results. Midwifery advocates are exulting that the study proves that midwifery care is superior to other models of care. Just one problem: that's not what the study looked at. The study compared midwifery-LED team care with other forms of team care. That's why the name of the study is Midwife-led versus other models of care for childbearing women.

This incident is instructive on two levels. First, it is an excellent example of why systematic reviews are NOT the gold standard of scientific evidence. Second, it shows how midwifery and "natural" childbirth advocates don't bother to read the scientific papers they cite, don't understand what they say, and promptly disseminate misinformation to others.

First, let's look at what the study was trying to investigate. According to the authors:
Midwife-led care has been defined as care where "the midwife is
the lead professional in the planning, organisation and delivery of care given to a woman from initial booking to the postnatal period". Some antenatal and/or intrapartum and/or postpartum care may be provided in consultation with medical staff as appropriate. Within these models, midwives are ... the lead professional ...
Here's how the authors describe the other models of care that served as the comparison group:
Care is often shared by family doctors and midwives, by obstetricians and midwives, or by providers from all three groups. In some countries ... the midwifery scope of practice is limited to the care of women experiencing uncomplicated pregnancies, while in other countries ... midwives provide care to women who experience medical and obstetric complications in collaboration with medical colleagues. In addition, maternity care in some countries ... is predominantly provided by a midwife but is obstetrician-led, in that the midwife might provide the actual care, but the obstetrician assumes responsibility for the care provided to the woman throughout her pregnancy, intrapartum and postpartum periods.
In other words, this study compared two different models of team care. This study did not compare midwife care to doctor care. Virtually every woman in both arms of the study was cared for by midwives AND doctors. The study only looked at the role of the midwife within the team.

Let's look at the problems within the study itself. As I mentioned above, systematic reviews are not the gold standard of scientific evidence. That's because they depend entirely on what studies are included, and which are excluded. How did the authors determine which studies to include in this review?
Our search strategy identified ... 31 studies for potential inclusion. Of those, we included 11 trials involving 12,276 randomised women in total ... Included studies were conducted in the public health systems in Australia, Canada, New Zealand and the United Kingdom with variations in model of care, risk status of participating women and practice settings...

Seven studies compared a midwife-led model of care to a shared model of care, three studies compared a midwife-led model of care to medical-led models of care and one study compared midwife-led care with various options of standard care including medical-led care and shared care.
Note that not a single study compared midwife care with doctor care.

How did the authors decide that only 11 of the 31 studies should be included, and the other 20 excluded? The authors never say. This review contains 130 pages of text and tables, and as far as I can determine, the authors offer no justification or even explanation for their decision to use only 11 of the 31 studies. It seems that they simply picked the studies they liked and excluded the ones they didn't like.

I'm rather surprised that the editors of the Cochrane Review were willing to accept this review. It conclusions are essentially useless because studies were included and excluded on an arbitrary basis, and the 11 studies that were included had wide variations in the comparison group. So this study tells us nothing about anything.

The bottom line is that is a poorly done study that is designed to compare midwife led team care with other forms of team care. Did it show that midwife-led care is superior to other forms of team care? The authors think that it did, but that may be simply because the data selection was biased.

One point, though, is undeniable. The study NEVER compared midwife care to doctor care. Therefore, midwifery advocates who are exulting that the study shows that midwife care is superior are only demonstrating that they never even bothered to read the study.


0 Old Comments: