Cadiotocography Combined With ST-analysis Versus Cardiotocography Combined With Scalp-pH

Hypothesis:

STAN monitoring will reduce the number of interventions because of suspected fetal asphyxia and reduce the number of newborns with metabolic acidosis.

Primary endpoint:

1) Frequency of metabolic acidosis in the two groups, defined by pH in umbilical cord artery < 7.05 and standard base excess <-10.

Secondary endpoints:

1. Number of intervention (VE and caesarean section) in the two groups
2. Number of pH measurements in the two groups
3. Number of neonates admitted to the neonatal department because of suspected asphyxia in the two groups

The aim of fetal surveillance is to identify those fetuses at risk for developing damage in newborn to term or long term damage caused by lack of oxygen during birth process. Approximately 1/10 of all cases of paralysis due to brain damage (cerebral palsy) is believed to be caused by lack of oxygen during birth. These can be avoided if the investigators intervene actively in the birth before damage occurs.

CardioTocoGraphy (CTG = detection of fetal heart rate pattern and maternal uterine contractions via electrodes on the maternal abdomen and fetal scalp) is a widely used method of fetal surveillance. However, it can be difficult to interpret a CTG, and uncertainty in CTG interpretation may therefore lead to increase in the number of deliveries with vacuum suction and caesarean section. Interpretation of CTG can be improved by analyzing the acidity of a blood sample taken from the skin of the fetal scalp. Such a scalp pH analysis shows indirectly the fetus gets enough oxygen. Scalp pH measurement requires expertise and requires repeated measurements if the abnormal heart rate pattern persists. This method is the normal routine at the maternity ward at Hvidovre Hospital / Roskilde County Hospital.

The problem seems to be partially alleviated by using a newly developed method for fetal surveillance called STAN (ST analysis). By STAN continuously recorded both CTG and fetal ECG (electrocardiography = recording of the electrical heart activity). Simultaneously analyzes a portion of the fetal ECG, namely ST-part because hypoxia leads to changes in it. The technique is easy to use, since it only requires one electrode on the fetal scalp that is placed in the same way as in ordinary CTG registration.