Way back in 2017, as I was in the first year of my PhD, I put together this short piece and sent it to a friend. I asked that she keep it safe and in the event that I died before the PhD was done, that she publish it on her blog. Fortunately, that didn’t come to pass! I rediscovered it in my hard drive recently and am pleased to be able to share it at last.
#1 CTGs don’t save baby’s lives
Women monitored by continuous cardiotocograph (CTG) monitoring during labour were no less likely to experience a stillbirth or a neonatal death than women monitored by intermittent auscultation (IA). Three women in 1000 experienced perinatal loss if they had CTG monitoring, and 3 in 1000 women experienced this outcome if they had IA (Alfirevic, et al., 2017).
Women who had a CTG performed on admission to hospital in labour had the same risk of experiencing the death of their baby (0.8 in 1000) as women who had IA only (0.9/1000) (Devane, et al., 2017).
Women who had a CTG performed in the antenatal period because of concerns about the wellbeing of their baby had a 23 in 1000 chance of experiencing the death of their baby. Women with the same concerns who had IA only had 11 chances in 1000 of experiencing this outcome (Grivell, et al., 2015). While the death rate was higher for women who had a CTG, it narrowly missed being statistically significant (95% confidence interval 0.95 to 4.42).
#2 CTGs don’t protect baby’s brains
Women monitored by continuous CTG monitoring during labour had 4 chances in 1000 that their baby would develop cerebral palsy. Women who had IA in labour had 2 chances in 1000 of the same diagnosis. While this rate was higher for women who had a CTG, it wasn’t a statistically significant outcome (95% confidence interval 0.84 – 3.63) (Alfirevic, et al., 2017).
While cerebral palsy has not been studied as an outcome of admission CTGs, there are no differences in any other outcome that indicate possible damage from low oxygen levels (Apgar scores, admission to neonatal intensive care, hypoxic ischaemic encephalopathy, or neonatal seizures) (Devane, et al., 2017).
Likewise, cerebral palsy has not been studied as an outcome for women having antenatal CTGs, but there were no difference in the rates of outcomes that might suggest possible brain injury (Apgar scores, admission to neonatal intensive care) (Grivell, et al., 2015).
#3 CTG use harms women
There is a tendency to see caesarean section as simply an alternate way to have a baby. If we view it as a complication of maternity care, one that exposes women to short term discomforts and complications and several long term risks (including stillbirth in the next pregnancy), then it becomes clear that the use of CTGs harms women.
The use of continuous CTG monitoring during labour increased the chance of caesarean section by 63%. The rate rose from 3.6% with IA to 5.4% in women with continuous CTG monitoring during labour (Alfirevic, et al., 2017). Note that the rate of caesarean section has increased significantly in the years since the research was conducted, so this is likely to under-represent the probability of caesarean section for women giving birth in hospitals with much higher rates.
The use of admission CTGs increased the chance of caesarean section by 22%, from 3.6% to 4.4% (Devane, et al., 2017).
The use of antenatal CTGs doesn’t alter the chance of caesarean section significantly (rate of 18.5% for IA and 19.7% for CTG use) (Grivell, et al., 2015).
#4 There is a lack of evidence to support the use of CTG monitoring during labour for women with risk factors
Five trials have assessed the usefulness of continuous CTG monitoring during labour for women with risk factors, with only 1,974 women were included (compared to 16,049 women without risk factors). This means that it is difficult to be sure whether continuous CTG monitoring during labour is of use for uncommon outcomes such as death or cerebral palsy. The Cochrane review (Alfirevic, et al., 2017) noted that there was no reduction in death rates, a statistically significant increase in cerebral palsy rates and a statistically significant increase in the caesarean section rates in women with risk factors who had CTG monitoring rather than IA.
(I have written more about this since the original version of this was written.)
The evidence suggests that the use of CTGs antenatally, at admission, or during labour doesn’t help babies, and it harms women. There is insufficient evidence to know whether there is a specific population of women who might benefit from the use of CTG monitoring.
Alfirevic, Z., Devane, D., Gyte, G. M., & Cuthbert, A. (2017). Continuous cardiotocography (CTG) as a form of electronic fetal monitoring (EFM) for fetal assessment during labour. Cochrane Database of Systematic Reviews (Online), 2, CD006066. http://doi.org/10.1002/14651858.CD006066.pub3
Devane, D., Lalor, J. G., Daly, S., McGuire, W., Cuthbert, A., & Smith, V. (2017). Cardiotocography versus intermittent auscultation of fetal heart on admission to labour ward for assessment of fetal wellbeing. Cochrane Database of Systematic Reviews (Online), 1, CD005122. http://doi.org/10.1002/14651858.CD005122.pub5
Grivell, R. M., Alfirevic, Z., Gyte, G. M. L., & Devane, D. (2015). Antenatal cardiotocography for fetal assessment. Cochrane Database of Systematic Reviews, 9(9), CD007863. http://doi.org/10.1002/14651858.CD007863.pub4