Fetal heart rate short term variation during labor in relation to scalp blood lactate concentration

Abstract

Introduction: Fetal heart rate short term variation (STV) decreases with severe chronic hypoxia in the antenatal period. However, only limited research has been done on STV during labor. We have tested a novel algorithm for a valid baseline estimation and calculated STV. To explore the value of STV during labor, we compared STV with fetal scalp blood (FBS) lactate concentration, an early marker in the hypoxic process. Material and methods: Software was developed which estimates baseline frequency using a novel algorithm and thereby calculates STV according to Dawes and Redman in up to four 30-minute blocks prior to each FBS. Cardiotocography traces from 1070 women in labor who had had FBS performed on 2134 occasions were analyzed. Results: In acidemic cases (lactate >4.8 mmol/L; Lactate Pro™), median STV 30 minutes prior to FBS was 7.10 milliseconds compared with 6.09 milliseconds in the preacidemic (4.2-4.8 mmol/L) and 5.23 milliseconds in the normal (<4.2 mmol/L) groups (P <3.0 milliseconds (n = 160) was 2.3 mmol/L. When 2 FBS were performed within 60 minutes the change rate of lactate correlated to STV (rho = 0.33; P