Fetal bradycardia in labor.

The prognostic significance of terminal bradycardia is analysed in this study. Amongst 12,145 intrapartal directly recorded cardiotocograms, 135 heart rate curves free of deceleration (1.1%) were found with an abruptly occurring fetal bradycardia. The mean duration of bradycardia was 5.7 +/- 3.1 minutes, the mean heart rate during the phase of bradycardia was 86.2 +/- 9.9 beats/minute. A premature amniotomy (40%) was significantly correlated with the bradycardia. The mean pH in the umbilical arterial blood was 7.261 +/- 0.072. pH values of less than 7.200 were measured in 21.7% and pH values under 7.150 were measured in 4.2%; a severe acidosis (pH less than 7.100) was not present in any case. The fall in fetal pH in the umbilical arterial blood per minute of bradycardia averages -0.006 units. In the bradycardia group, only 5.2% of all babies were slightly depressed and only 0.7% were severely depressed; 5.9% of the babies had slight difficulties in postpartal adaptation. It is concluded from the data that as a rule the impending spontaneous delivery (head rotated correctly, effective bearing-down efforts) can be waited for in the occurrence of terminal bradycardia (without prior decelerations). The fall in heart rate should not automatically occasion the institution of hazardous delivery maneuvers which may entail a greater danger to the mother and baby than the fetal bradycardia itself.