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ST-analysis versus fetal blood sampling (FBS)

Go to the STAN website.

Cardiotocography (CTG) is worldwide the method for fetal surveillance during labour.However, CTG alone shows many false positive results and without fetal blood sampling (FBS) it results in an increase in operative deliveries without an improvement of fetal outcome. FBS requires additional expertise, is invasive and has often to be repeated during labour. Two RCTs have shown that a combination of CTG and non-invasive ST-analysis (of the fetal ECG) reduces the rates of metabolic acidosis and instrumental delivery. However, in both RCTs FBS was still performed in both arms, and it is therefore still unknown if the observed results were indeed due to the ST-analysis or to the use of FBS in combination with ST-analysis.
To quantify costs and effectiveness of non-invasive monitoring (CTG + ST-analysis) as compared to normal care (CTG + FBS), in order to judge whether the ST-analysis can replace FBS.

Study design
Multicentre randomised controlled trial in eight hospitals.

Study population
Women in labour (above 36 weeks of gestation) with an indication for CTG.

Women will be randomised for fetal surveillance with CTG + FBS or CTG + ST-analysis.

Outcome measures
Primary outcome is the incidence of metabolic acidosis (defined as pHbelow7.05 and BDecf above 12 mmol/l in the umbilical cord artery). Secondary outcome measures are: instrumental delivery rate, cost-effectiveness,neonatal outcome (Apgar score, admission to a neonatal ward) and cost-effectiveness of both monitoring strategies across hospitals.

Power/ data analysis
The analysis will follow the intention to treat principle. The incidence of metabolic acidosis will be compared across both groups. Assuming a reduction of metabolic acidosis from 3.5 to 1.5 %, using a two sided test with an alpha of 0.05 and a beta of 0.80, in favour of CTG +ST-analysis, 2400 women have to be randomised (1200 per group).

Economic evaluation
The economic evaluation is designed as cost-effectiveness analysis, i.e. the ratio of (I) incremental costs and (II) the reduced rate of metabolic acidosis, associated with the strategies is quantified.

Time schedule
The total research period is 3 years: a start-up phase of 4 months, an inclusion period of 26 months and 6 months to realise follow-up, analysis and reporting.

Dr. A. Kwee, gynaecologist, UMC Utrecht
Dr. G.H. Blijham, gynaecologist, UMC Utrecht
Drs. S.M.C. Vijgen, AMC

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