Last week I shared two different research papers highlighting a link between epidural use and caesarean section for abnormal fetal heart rate patterns, pointing out that how these things were connected was not explained by this research. An independent group of researchers, based in Italy, have also recently published research in this area, and their findings provide some additional clues about what might be going on (Ghidini et al., 2023).

How was the research done?

Data from women who used an epidural for pain management during labour at one hospital were gathered from hospital records. Women with a multiple pregnancy, stillbirth, a fetus in a position other than head first, or who were less than 37 weeks pregnant at the time of labour were not included in the data set. Information about blood pressure readings after placement of the epidural, changes in fetal heart rate patterns (presumably recorded by CTG but not explicitly stated in the paper), and the use of approaches to manage low blood pressure (intravenous fluid bolus, oxygen administration, changes in the woman’s position, or administration of ephidrine – a drug to increase blood pressure) were collected, along with the way the baby was born. The fetal heart rate pattern was independently reviewed by one reviewer who was blinded to the outcome of the birth and categorised according to the American College of Obstetricians and Gynecologists guidelines. The relationship between changes in blood pressure and fetal heart rate patterns were explored.

What did they find?

439 women were included in the study. A significant drop in blood pressure happened for 36% of women. Severe decelerations were more common when blood pressure dropped (happening for 16% of women). Severe decelerations also occurred when there was no major change in blood pressure (happening for 9% of women), so blood pressure changes were not the only factor relating to the appearance of decelerations.

Having an epidural at lower cervical dilatation, having a longer duration of labour after the placement of an epidural, and having an abnormal fetal heart rate pattern were all associated with higher rates of use of caesarean section. The relationship between the presence of an abnormal heart rate pattern and caesarean birth remained even when the data were corrected to take into consideration whether blood pressure had fallen or not.

What does this mean?

In they discussion section of the paper, the authors do a great job of examining previous evidence about the relationship between caesarean birth and epidural use – pointing out increasingly strong evidence that epidurals DO increase the use of caesarean section. If you are able to access a full-text copy of the paper, it is worth reading this. At least one of the pathways responsible for this link is an epidural related drop in blood pressure, reducing blood flow to the placenta, and therefore dropping fetal oxygen levels. Efforts to compensate for lower oxygen levels produce decelerations via the peripheral chemoreceptor reflex, and obstetricians respond to this by recommending caesarean section. Whether these decelerations are linked to worse outcomes for the fetus / baby if caesarean section is not performed is not known.

It is important to include information about higher rates of caesarean section, and higher rates of abnormal heart rate patterns, when providing information to women about pain management options during labour. More research is needed to understand what the mechanism is for post-epidural heart rate abnormalities when blood pressure readings do not fall.

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References

Ghidini, A., Vanasche, K., Cacace, A., Cacace, M., Fumagalli, S., & Locatelli, A. (2023). Side effects from epidural analgesia in laboring women and risk of cesarean delivery. American Journal of Obstetrics & Gynecology Global Reports. https://doi.org/10.1016/j.xagr.2023.100297 

• What happens to women after they leave the birth room?
• What stops professionals from using intermittent auscultation?

Categories: CTG, EFM, New research

Tags: Blood pressure, caesarean section, Decelerations, hypotension