Systolic time intervals in the nonasphyxiated fetus.

The preejection period (PEP) of the cardiac cycle of nonasphyxiated fetuses was evaluated to determine the range of normal to be expected during labor. Standard techniques using the filtered Doppler cardiogram and internally obtained fetal electrocardiogram (ECG) were used. It was demonstrated that the PEP is correlated, although poorly, with heart rate. There is no correlation with fetal weight. The variance from fetus to fetus is quite large. It is concluded that a single measurement of PEP may not be helpful in the determination of fetal hypoxia, since the range of normal varies widely.