Fetal blood sampling has dropped out of practice, or reduced in use, in many parts of the world. It other places it remains a staple part of obstetric practice. This is a living example that far more than evidence alone is what drives practice. The evidence-base for fetal blood sampling was never very strong – and new research remains important to understand whether fetal blood sampling is a useful part of fetal monitoring practice or not.
A team from Finland recently published a study on 20 years of experience with fetal blood sampling (Pietilä et al., 2026). Let’s look at their research.
What they did
During the period January 2002 to December 2001, 46,953 babies were born at a single tertiary facility in Finland. Women with multiple pregnancy, gestational age less than 33 weeks, caesarean section prior to labour, or vaginal breech births were excluded, leaving 40,309 women / baby pairs. Among this group of women, 3,486 had at least one fetal blood sample performed (8.6%). Both pH testing and lactate testing had been used during this period, with lactate testing introduced in 2011.
A significant change in the FIGO guideline used at the hospital occurred in 2015, followed by more attention to fetal monitoring education.
The research team looked at how often fetal blood sampling was used in four time blocks, and compared this to outcomes for mothers and babies from each time block. No correction for potential confounding variables was used in the data analysis.
What they found
The use of fetal blood sampling fell over time: from 11.7% of all births in 2002 – 2006 down to 3.9% in the period 2017 – 2021. During the same time period, caesarean section during labour fell from 8.4% to 4.3%, and vaginal birth rates increased from 83.6% to 87.6%, with no change in the use of instrumental birth. The use of induction of labour increased from 2% to 36.4%.
Doctors diagnosed “asphyxia” less often over time: falling from 0.9% of births in the first time period to 0.4% in the most recent. There was a small increase in the incidence of Apgar scores of less than seven at five minutes (from 1.6% to 1.8%). The rise was larger for women who did not have fetal blood sampling. Rates of admission to the neonatal intensive care unit fell (from 15.9% to 9.2%). No changes in the perinatal mortality rate were seen (with an average over the 20 years of 4 in 10,000 births).
What this means
Studies like this need to be considered with caution. Many things change in clinical practice over time. A new guideline. A new consultant that teaches and encourages a particular approach to care. A change in the population of women using the service. Placing the weight of responsibility for changes in birth outcomes on one aspect of care alone – in this case fetal blood sampling – is asking a lot from it. The authors of this study acknowledge that this is the case, and call for large, well-designed studies on fetal blood sampling to be conducted.
Saling introduced fetal blood sampling in the early 1960s, just prior to commercially available CTG monitoring appearing on the scene (Saling, 2006). That’s over sixty years ago. Sixty years of time to get around to assessing the technology to properly understand whether it works as intended, and to understand any harms it causes. In that time there have been two very small randomised controlled trials that didn’t answer those questions.
It keeps happening
I see this over and over again. Commonly used types of fetal monitoring that are never adequately assessed before becoming accepted practice. Fetal spiral electrodes, central fetal monitoring, telemetry, and fresh eyes checks are all examples of this.
There are also studies that raised questions of huge importance that should have prompted further research but never have. Like the preterm birth study that showed babies who were allocated to CTG monitoring much higher rates of cerebral palsy than those monitored by intermittent auscultation (Shy et al., 1990). Here we are, 36 years later, with international guidelines still recommending CTG use in preterm labour despite the only study ever done showing it was harmful.
It begs the question of why there has been no appetite to ground this area of practice on solid evidence. Clearly the social forces that saw CTGs introduced into practice are still in operation today. Will there ever be enough of a regime change so we see an acknowledgement of the scale of the problem and a plan to solve it?
Decisions about fetal monitoring are for YOU to make. This is true whether you are considered “high risk” or not. It remains true even when someone tells you that you don’t have a choice and that CTG monitoring is mandatory. My recently published book Monitoring your baby in labour: An evidence-based guide to help you plan your birth supports you to make these decisions.
Buy your copy today
References
Pietila, S., Monkkonen, A., Backman, H., & Keski-Nisula, L. (2026). Twenty-year trends in fetal scalp-blood sampling and birth outcomes: A single-center retrospective cohort study of 40 309 women in labor. Acta Obstetrica et Gynecologica Scandinavica, 105(2), 346-355. https://doi.org/10.1111/aogs.70110
Saling, E. (2006). Fetal blood analysis during labour. American Journal of Obstetrics & Gynecology, 194(3), 896-899. https://www.ajog.org/article/S0002-9378(05)00785-4/fulltext
Shy, K., Luthy, D., Bennet, F., Whitfield, M., Larson, E., van Belle, G., Hughes, J., Wilson, J., & Stenchever, M. (1990). Effects of electronic fetal monitoring as compared with periodic evaulation on the neurological development of premature infants. New England Journal of Medicine, 322(9), 588-593.
Categories: CTG
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