A Systematic Review of Labour Pain Used as an Outcome Criterion in Clinical Research

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Research on labour pain currently uses standard scores such as numerical scales as clinical outcomes, but no clear guidelines for such assessment have appeared since a review published in 1998. We wished to describe and estimate the quality of the methods used to assess and analyse such outcomes, in a systematic review of 215 comparative studies published since then, in 27 influential journals.


In addition to a complete description, we created for each study a composite “analysis quality score” (AQS) based on the methods of both measurement of pain/analgesia, and statistical analysis. AQS was tested against various factors, including a “design quality score” (DQS) created to estimate methodological quality (regardless of the analysis of pain intensity).


Both the AQS and its “measurement” component increased with the year of publication, as well as the DQS. The impact factor correlated only with the statistical component of the AQS, and with the DQS. However, the mean AQS and DQS were respectively at 43% and 75% of their maximal possible value, and these two scores were not correlated. The intensity of labour pain (or pain relief) was the primary outcome in 19% of the studies. While most of the studies actually used numerical scales, the methods of analysis were heterogeneous. When a cut-off point was determined to define analgesia, this was the most often 30% of the maximal value.


This review points out the need for a better standardisation of the methods in this field of research.

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