The slope of fetal heart rate deceleration is predictive of fetal condition during repeated umbilical cord compression in sheep

Abstract

The relationship between components of fetal heart rate deceleration and fetal arterial blood gas values or plasma catecholamine concentrations was investigated by repeated complete umbilical cord compression in chronically instrumented fetal lamb. Fetal arterial pH and bicarbonate levels decreased, while plasma norepinephrine and epinephrine concentrations increased more than tenfold. The slope of the descending limb of the fetal heart rate deceleration curve decreased and correlated strongly with fetal arterial pH, bicarbonate, and logarithmic plasma norepinephrine and epinephrine concentrations. Fetal arterial pH and bicarbonate levels were significantly lower in the group with lower fetal heart rate deceleration slope, and a greater plasma catecholamine concentration in this group suggested a redistribution of blood flow to vital organs. Therefore, during repeated umbilical cord compression, the fetal acid-base and hormonal state was predicted by the fetal heart rate deceleration slope. This relationship may be applicable to human fetuses in the diagnosis of fetal distress caused by umbilical cord compression during labor.