The STAN™ methodology
Being born is one of the greatest challenges in life and temporary oxygen deficiency is a normal part of labour. In most cases, a healthy fetus is able to handle this situation, but occasionally a fetus suffers severely. As a result, brain damage and even death may occur.
The strength of CTG is to recognise the healthy fetus and identify the very rare situation of the non-reactive, fetus suffering from chronic hypoxia. However, when abnormalities appear in the CTG pattern, it becomes difficult to evaluate the fetal hypoxic status. In this situation, an automatic ST waveform analysis guides the staff until delivery.
The STAN methodology has been developed to provide midwives and doctors with more detailed information about the fetal hypoxic situation during labour. It combines standard CTG technology with the new ST waveform analysis of the fetal ECG. This combination of CTG and ST enables the more precise identification of fetuses suffering from hypoxia and allows for accurate and consistent intervention. The STAN methodology provides improved sensitivity as well as specificity, saving suffering fetuses and avoiding unnecessary intervention.
Fetal ECG is obtained via a scalp electrode. Changes in the T wave and the ST segment of the fetal ECG are automatically identified and analysed. An increase in T wave amplitude, in relation to QRS amplitude, corresponds to the utilisation of glycogen stores and thereby to myocardial anaerobic metabolism. Since anaerobic metabolism is the prime fetal defence against hypoxia, the T/QRS ratio provides direct information about the fetal situation.
Two large randomised controlled trials have been conducted, involving a total of 6873 deliveries evaluating the outcomes of births monitored with STAN. The initial Plymouth trial from 1993 revealed a safe reduction of 46% in operative deliveries due to non-reassuring fetal status1. The Swedish multi-centre trial in 2001, verified the reduction in operative intervention but also demonstrated the ability of the STAN methodology to reduce the number of babies born with metabolic acidosis by 75%2. A third trial focused on the newborn babies with complicated or adverse neonatal outcome and showed a significant decrease of cases from 0.33 % in the CTG-only group to 0.04 % in the CTG plus ST group3.
Please see publications here.
View Stan Cases here.
1 Westgate J et al. Plymouth randomized trial of cardiotocogram only versus ST waveform plus cardiotocogram for intrapartum monitoring in 2400 cases. Am.J.Obstet.Gynecol. 1993;169:1151-60.
2 Amer-Wåhlin et al. Intrapartum Fetal Monitoring: Cardiotocography versus Cardiotocography plus ST Analysis of the Fetal ECG. A Swedish Randomized Controlled Trial. Lancet 2001;358:534-38.
3 Norén et al. Fetal electrocardiography in labour and neonatal outcome: data from the Swedish randomised controlled trial on intrapartum fetal monitoring. Am.J.Obstet.Gynecol. 2003, 188:183-192.