In the linked article, Kessler et al. quote Neilson's review (Cochrane Database Syst Rev 2013;5:CD000116) that ‘use of ST waveform analysis of the fetal ECG (STAN) as an adjunct to CTG has been found to reduce the frequency of vaginal operative deliveries, the necessity of fetal blood sampling and the frequency of neonate transferal to the neonatal intensive care unit (NICU)’. However, they fail to report that the same review found no significant difference in caesarean section rate, severe metabolic acidosis (pH <7.05) at birth, or neonatal encephalopathy, arguably more important endpoints. All but one of the randomised trials excluded breech presentation, so the hypothesis that STAN would be of value with breech presentation was worth testing. Eliot and Hill in 1972 (Br Med J;4:703–6) demonstrated the feasibility of measuring pH on a buttock blood sample in 30 cases, and Wheeler and Greene in 1975 (Br J Obstet Gynaecol;82:208–14) confirmed the appropriateness of fetal heart rate (FHR) monitoring in 42 cases of breech labour, so it seemed a priori likely that STAN would be useful in cases where a vaginal breech birth was anticipated. STAN was used to monitor fetal condition in 69% of women selected for attempted vaginal delivery, resulting in a sample size of 433. Application was straightforward, and there was an interpretable signal in 94.7% (compared with 96.8% for cephalic presentations). However, despite the expected higher rates of umbilical cord artery pH <7.05 (6.6% for breech versus 2.6% for cephalic presentations) and encephalopathy (1.6% versus 1.05%), the rates of a rise in baseline T/QRS (38.8% versus 47%) and episodic T/QRS (10.3% versus 11.4%) were lower, although the incidence of biphasic ST was higher (16.9% versus 10.9%). This might in part relate to the difference in the ECG signal orientation when recorded from the buttocks rather than the head, and in part to differences in gestational age and birthweight (the latter cannot be allowed for in real time because it is unknown during labour). Importantly, in two of the three breech cases of moderate/severe encephalopathy, there were no STAN indications of hypoxia prior to birth. Similar findings have previously been reported in relation to cephalic presentations (Westerhuis et al, BJOG 2007;114:1194–201) and Kessler et al. note a similar disconnect between a preterminal CTG and STAN changes in labour complicated by diabetes or sepsis. They comment that ‘CTG (cardiotocogram, fetal heart rate and contraction monitoring) remains the basic method in STAN monitoring’ and, unlike a rise in T/QRS, ‘a preterminal CTG as a primary indicator of hypoxia was more common in breech than in cephalic presentations’, consistent with the higher incidence of neonatal acidosis and encephalopathy. Kessler et al. have shown that STAN monitoring is feasible in breech presentations but that the results can be more difficult to interpret than in cephalic presentations, and expertise in CTG pattern interpretation must remain the priority. Monitoring breech labour is not an additional indication to institute STAN monitoring in your unit if you are not already using it.
Disclosure of interests
I have no conflicts of interest to declare.