In 2011, Professor Susan Bewley and Dr Lin Foo wrote a chapter titled “Are doctors still improving childbirth?” in the book Birth Rites and Rights. They referred to the economic concept known as the law of diminishing returns. The chapter examined the rise in maternal mortality rate and the stagnation in the reduction of the perinatal mortality rate that has been noted in most high-income countries over the past few decades, exploring the reasons behind it. I read the chapter recently, and their arguments are even more compelling almost a decade later.
The law of diminishing returns
In economic terms, it is relatively easy and cost effective to improve the efficiency of a poorly performing production system. For example, enclosing tomato growing land in climate controlled irrigated hothouses that exclude pests increases the yield per square metre many times over and quickly offsets the capital investment to build the hothouse. To take an already productive system and produce additional improvements in efficiency becomes increasingly expensive, and the improvements in efficiency are smaller. At some point, further attempts at improving the system tip the cost-benefit ratio so that further investments generate only cost and no further benefit. This is the law of diminishing returns.
The last century has seen the rise and rise of intervention in birth. Initially, a relatively low rate of intervention was effective in producing large improvements in both perinatal and maternal outcomes, in particular mortality. But as time has progressed the rate of birth interventions has increased while improvements in outcomes in high-income countries have largely stalled (Molina et al., 2015). There are also clear indicators that maternal outcomes are becoming worse in some high-income countries (MacDorman, et al., 2016).
A different approach is needed
It is increasingly clear that doing more in maternity care – screening more, educating more, surveilling more, intervening more – is unlikely to produce more benefits. Yet this continues to be the approach that is being used in the maternity care systems of high-income countries. The gathering together of several different interventions into bundles such as the perineal care bundles and those directed at reducing the perinatal mortality rate are examples of attempts to pursue further improvements by doing more.
Bewley and Loo suggested that public health approaches might be a better way to make progress in improving outcomes for women and babies. Ensuring opportunities for meaningful employment, adequate housing, access to reproductive healthcare, and freedom from violence offer broad based improvements for women’s lives in addition to having the potential to address many of the social determinants of poor perinatal and maternal outcomes. They also point out that improved governance can support midwife led, community delivered, primary maternity care and provide obstetric staff with a sense of security to reduce the use of interventions for which there is little evidence of benefit.
The complex physiology of pregnancy and childbirth cannot be changed. It is only by using a public health lens to look at the antecedents, associations and context of pregnancy and applying an evidence-base to maternity care systems that medicine can deliver improvements in outcomes.p. 72
Reducing intrapartum CTG monitoring use
Intrapartum CTG monitoring is a clear example of an intervention which causes harm and provides little benefit. Over the past fifty years there has been a progressive increase in the frequency of use of intrapartum CTG monitoring and in the complexity of the technology used for monitoring. In the face of evidence that it has not yielded the promised benefits, the approach has been to do more, rather than less. Indications for use of CTG monitoring have expanded, central fetal monitoring, ST analysis, and computer interpretation of the CTG have been introduced in various places around the world. Educational programs about CTG monitoring have become longer, and are increasingly considered as mandatory for employment, often with an assessment of knowledge attached to the program. When new evidence demonstrates that these additions are ineffective, no action is taken to roll back to less intervention.
Viewed through the framework of the law of diminishing returns, it is easy to see that attempting to do more, and more, is not appropriate. Maternity care organisations such as obstetric colleges and perinatal societies could provide a path out of the cycle of escalation, by providing clear statements of support for evidence based intrapartum fetal monitoring approaches such as intermittent auscultation. Will they step up to this challenge in the next decade?
Bewley, S. & Foo, L. (2011). Are doctors still improving childbirth? In F. Ebtehaj, J. Herring, M. Johnson, & M. Richards (Eds), Birth Rites and Rights. Hart Publishing.
MacDorman, M. F., Declercq, E., Cabral, H., & Morton, C. (2016, Sep). Recent increases in the U.S. maternal mortality rate: Disentangling trends from measurement issues. Obstetrics and Gynecology, 128(3), 447-455. https://doi.org/10.1097/AOG.0000000000001556
Molina, G., Weiser, T. G., Lipsitz, S. R., Esquivel, M. M., Uribe-Leitz, T., Azad, T., Shah, N., Semrau, K., Berry, W. R., Gawande, A. A., & Haynes, A. B. (2015, Dec 1). Relationship between cesarean delivery rate and maternal and neonatal mortality. JAMA, 314(21), 2263-2270. https://doi.org/10.1001/jama.2015.15553