Cardiotocography combined with ST analysis versus cardiotocography combined with fetal blood sampling in deliveries with abnormal CTG: a randomized trial

Purpose The aim was to investigate if intrapartum monitoring with cardiotocography (CTG) in combination with ST analysis (STAN) results in an improved perinatal outcome. Methods We performed a two-center randomized trial. 1013 women with term fetuses in cephalic presentation entered the trial. If a CTG showed intermediate or pathological abnormalities, they were offered fetal blood sampling (FBS) and inclusion if the pH value was above 7.25. They were randomized to either CTG + FBS or CTG + STAN. The primary outcome was neonatal metabolic acidosis, defined as umbilical cord arterial blood pH below 7.05, and base excess equal to or below -10. The secondary outcomes included operative vaginal delivery for fetal distress. Results The rate of metabolic acidosis was 0.8% in the CTG + PBS group and 1.5% in women in the CTG + STAN (P = 0.338). More women in the CTG + STAN group delivered by operative vaginal delivery (25.6% vs 33.5%, P = 0.006). Significantly fewer women in the CTG + STAN group had three to five (28.8% vs 11.0%, P = < 0.001) and six to ten fetal blood samples taken (3.4% vs 0.4%, P= < 0.001). Conclusion CTG + STAN did not reduce the incidence of neonatal metabolic acidosis compared to CTG + FBS. CTG + STAN was, however, associated with an increased risk of operative vaginal delivery and a reduced use of FBS. If STAN is used for fetal surveillance, we recommend that it is combined with other methods, such as FBS, for confirmation of the need for operative delivery.

Automated summary

Intrapartum monitoring with cardiotocography (CTG) in combination with ST analysis (STAN) did not reduce the incidence of neonatal metabolic acidosis compared to CTG in combination with fetal blood sampling (FBS). However, CTG + STAN was associated with an increased risk of operative vaginal delivery and a reduced use of FBS.