[The short-term variability index from abdominal fetal electrocardiogram]

Fetal heart rate monitoring was carried out on 37 patients between 34 and 42 weeks gestation, in 21 patients with direct fetal electrocardiogram (dFECG), and in 16 patients with abdominal fetal electrocardiogram (aFECG). The mean of the absolute beat by beat differences (MABB) and the percentage of beat by beat differences below 1 millisecond (1 msec%) and below 2 milliseconds (2 msec%) were measured from true fetal R-R intervals by a computerized technique. With dFECG, a significant inverse correlation was found between the MABB and the 1 msec% or the 2 msec%. The standard deviation of fetal R-R intervals as the LTV index showed a higher correlation to the MABB than to the 1 msec% or the 2 msec%. These results were similar to those with aFECG. In addition, with aFECG, the effect of fetal rest and activity on the MABB was significant, but the 1 msec% and the 2 msec% were not altered with periods of fetal rest and activity. The influence of the artifact in aFECG signals on the 1 msec% and the 2 msec% was less than on the MABB. The 1 msec% and the 2 msec% were reliable indices of the STV assessment from aFECG.