CTG or STAN--with or without FBS?

Abstract

Fetal monitoring is a fundamentally important but stillcontroversial topic in obstetrics. In obstetrics there is akind of “tradition” of introducing methods of surveillanceor intervention before we have proper evidence for theproposed benefit. Fetal blood sampling (FBS) and ST-analysis + cardiotocography (CTG) (STAN) is no excep-tion. Actually, we never even had evidence, at least notfrom randomized controlled trials (RCTs), that CTG wasbetter than intermittent auscultation in terms of fetal out-come before it was widely distributed and ingrained inclinical practice in high- and even medium-resourcecountries. We do know that in controlled prospective tri-als the rates of cesarean section and operational deliveryincreased after introduction of electronic CTG, but thisdoes not seem to have improved fetal/neonatal or long-term outcome to any significant degree (1). We have sev-eral different consensus algorithms for the interpretationof CTGs, and we use most of our time in the obstetricunit to discuss and interpret CTG traces.Therefore, the promising results of the first RCT stud-ies of STAN raised enthusiasm among obstetricians. Butsubsequent trials and meta-analyses showed divergentresults. In the autumn 2013, a courageous colleague inMalm€o invited international speakers to a Pro and Conconference on FBS and STAN, and we decided to invitethese speakers to write commentaries for this theme issue.The STAN method has been evaluated by five differentRCTs, and five systematic reviews with meta-analyseshave been published – with different results. To presentthe background material we have agreed to publishreviews describing both the RCTs and the meta-analyses.Since there is a subjective approach involved regardless ofwho is the author, we have invited a leading academicfrom each of the Nordic countries where the STAN hasbeen in use to comment on the presentation of the RCTsand meta-analyses. These comments appear after the rele-vant two articles.The aim of this theme issue is not to provide clear-cutrecommendations or definite answers as to whether toapply FBS and or STAN in clinical practice as adjuncts toconventional CTG monitoring. We wanted to present thepros and cons for both fetal monitoring methods. We areaware that the intense debate that followed the publica-tion of the dominant Swedish study was sensitive andeven emotional, especially considering our usually coolNordic temper.But still, the way we apply fetal monitoring in laborand interpret the CTG traces is an essential part of ourdaily work with midwives in the delivery ward. It isimportant for all of us. Some find it counterproductivethat FBS is even used to confirm or supplement theresults obtainable by STAN. Others do not believe inSTAN and advocate continued use of CTG and FBS formeasuring pH, base excess and/or lactate levels.The development of STAN was based on many years ofpublished experimental research. We know less about thebackground for decisions on the renewed specific inter-pretation of the CTG that was instituted by implementingSTAN monitoring. We do not know enough about howthe STAN concept was developed. What was the back-ground material that led to the definition of “significant”STAN events and how significant were they in the mate-rial of deliveries used for development of the concept?How did the researchers decide on a baseline rise of 0.06as significant – why not 0.05 or 0.08? To some obstetri-cians, STAN is only a vehicle towards understanding aCTG that puzzles you and makes you scrutinize the pat-tern. But the absence of a clear background and the lackof transparency convey a sense of a Magic Black Box. Ingeneral terms the algorithm tells you that an ST eventloses its significance if the CTG is normal – thus theCTG “overrules” the ST analysis unless you have a patho-logical CTG trace with no ST events. The exception iswhen the trace is very pathological (pre-terminal), as theST registration is then considered useless. The non-intui-tive method occupies a lot of intellectual capacity, andthe clinical focus on the screen and the complex algo-rithm gets priority before the proactive support for themother and before the required focus on the progress oflabor, which so often is different from the linear averagedepicted in a partogram.The FBS conveys a sense of knowing the true state ofthe fetus. The human inclination to perceive linear rela-tions and development, extrapolating from the average to