Data from five years of clinical usage of ST Analysis and Stan at the Labour and Delivery ward at Haukeland University Hospital in Bergen, Norway is reported in this prospective observational study. The study was defined as a project of quality improvement, and included a total of 22,475women selected for vaginal delivery.
Fetal monitoring was administered according to perceived risk; high risk labour was monitored by CTG+ST Analysis while low risk labour was monitored by auscultation or CTG alone. The proportion of Stan monitored deliveries gradually increased from 21.2% to 33.7%, mainly due to improved case selection procedure. Fetal blood sampling was used only in 2.4% of the Stan monitored deliveries. Optimal signal quality was obtained in 81.7% of the Stan cases.
The proportion of cord metabolic acidosis decreased from 1.4% to 0.3% in the high risk Stan group, and a majority of these cases had an operative delivery. Stan clinical guidelines indicated intervention in 30 of the 37 cases of cord metabolic acidosis and in five of these there was no ST information during the last 20 minutes prior to delivery. In all 4% of infants were transferred to NICU and 38 new-born had a diagnosis of neonatal encephalopathy. Of these 38 cases, 24 were monitored with ST Analysis; delayed intervention was present in ten cases and obstetric or neonatal catastrophe had a substantial impact on outcome in four of the cases.
The total proportion of operative deliveries also decreased during the study period. There was a clear association between the increased monitoring with ST Analysis and the decreasing rate of operative interventions in the low risk population. The total rate of cesarean section decreased from 10.1% to 8.8% in the birth population during the study period. The rate of emergency cesarean section remained stable.
Proportion of emergency cesarean section deliveries by year of birth and monitoring method (Stan or auscultation/CTG; columns) and proportion of Stan monitored deliveries (line).
The authors conclude that ST Analysis and Stan was a useful tool for identifying fetuses at risk of intrapartum hypoxia, and that despite a very low use of fetal blood sampling there was a low proportion of cord metabolic acidosis and new born morbidity.
