Do people agree on antenatal CTGs?

There has been a lot of research about whether health professionals agree on what to call the pattern on a CTG during labour. And the experts all agree, that the experts don’t agree. That is to say, there is a troubling degree of variability in how maternity professionals interpret the same CTG pattern. This is something I have written about before (here, here, and here).

Until recently, I had never seen any research about how maternity professionals do when they are interpreting CTG patterns during pregnancy, rather than in labour. CTG interpretation SHOULD be easier during pregnancy as the range of abnormal patterns that occur is not as wide as it is during labour. I’m pleased to report there is new research from the Netherlands that set out to answer this question.

What did they do?

Maternity professionals in the Netherlands who had experience and education in antenatal CTG interpretation were asked to participate, with 47 taking part. The group included primary care midwives (who work in the community and care for women with uncomplicated pregnancies – 25%), hospital-based midwives (25%), residents (28%, and specialist obstetricians (22%). Each person was given ten antenatal CTGs along with clinical information about the woman and her pregnancy. One month later, they were presented with the same ten CTGs, but in a different order. A classification system based on the FIGO intrapartum guideline was used to structure the interpretation of the CTG (the details are set out in the paper). The test used to describe the degree to which people were consistent in their interpretation was the proportions of agreement test.

What did they find?

The proportions of agreement test was moderately good when professional groups were compared to one another for their ability to agree on the overall categorisation of the CTG, and higher than has been reported in previous research that included CTGs during labour (test results ranged from 0.82 to 0.94). Agreement was highest for residents and lowest for obstetricians, with little difference between midwives who worked in primary care and those working in the hospital.

Intra-observer variability was also measured (testing whether the same person interprets the CTG differently at different times or not). Professionals did slightly better here, with proportions of agreement from 0.86 to 0.94).

What does this mean?

Maternity professionals interpretation of antenatal CTGs is fairly consistent, both from one professional to another, and for the same person from one time to another. The finding that midwives and residents are more consistent in their interpretation than obstetricians has been noted in other studies. As the authors point out – higher levels of agreement don’t necessarily mean the interpretation is correct – everyone could agree and all get it wrong. There’s also no evidence to suggest that maternity services with higher levels of agreement when CTGs are interpreted do better in terms of perinatal or maternal outcomes.

It is a nice little study that extends research in a direction that has received little attention.

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References

Neppelenbroek, E. M., van der Heijden, O. W. H., de Vet, H. C. W., de Groot, A. J. J., Daemers, D. O. A., de Jonge, A., & Verhoeven, C. J. M. (2024, Mar 22). Inter- and intraobserver agreement of antenatal cardiotocography assessments by maternity care professionals: A prospective study. International Journal of Gynaecology & Obstetrics, in press. https://doi.org/10.1002/ijgo.15497