ST-analysis of the fetal ECG versus CTG only: a randomised clinical trial
The Dutch randomised controlled trial (Dutch RCT) was presented by Michelle Westerhuis in her thesis on 7th of January 2010. The results are very positive and Dr. Westerhuis concludes: “Intrapartum fetal monitoring by CTG+ST of the fetal ECG substantially decreases the incidence of (metabolic) acidosis.”
The study included 5 681 high risk patients, randomly assigned to either monitoring by CTG or CTG+ST Analysis. The primary outcome of the study was metabolic acidosis, defined as pH < 7.05 and Base Deficit in extracellular fluid (BDecf) > 12mmol/l. The result also includes metabolic acidosis calculated in blood (BDblood). Other secondary outcomes were operative deliveries, Apgar scores, admissions to NICU and number of FBS.
There was a 30% reduction of metabolic acidosis in the CTG+ST Analysis group. When base deficit was calculated in blood there was a significant reduction in metabolic acidosis with 44 %. At the same time, there was a 48% reduction in the use of FBS in the CTG+ST arm. These effects were achieved without any increase in operative deliveries. There were no effects on other neonatal outcomes. These results are consistent with the results of the meta-analysis of earlier randomised trials published in the Cochrane report.
The Dutch RCT was powered on the assumption that 3.5% of newborn would have metabolic acidosis at birth. In reality, the rate was much lower (1.1% in the CTG arm and 0.7% in the CTG+ST Analysis arm), explaining why the 30% reduction in primary outcome, although substantial, did not reach statistical significance. The 44% reduction in the metabolic acidosis in blood was however significant.
There is no consensus which method to use for calculating base deficit and metabolic acidosis: in the intracellular fluid or in blood. Researchers mostly use the first method, while in clinical practice the second is most common (since it is automatically calculated by most blood gas analysers). Both methods showed a substantial reduction of metabolic acidosis in the CTG+ST arm.
The Dutch RCT is one of the largest trials ever within obstetrics. It was performed in nine centres: three academic hospitals and six non-academic teaching hospitals. Most hospitals in the study did not have any previous experience of STAN. The study was performed without any involvement from Neoventa.Intrapartum fetal monitoring by ST-analysis of the fetal ECG.