The pre-ejection period as an antepartum indicator of fetal well-being.

A preliminary study was made of the potential usefulness of the pre-ejection period (PEP) as an antepartum indicator of fetal well-being. PEP was evaluated in 108 subjects over a 2-year period. It is essential to correct for the effects of heart rate and gestational age on PEP before attempting to relate it ot fetal status. From the control group of 95 fetuses within our study, an equation to correct PEP to a standard heart rate of 140 beats per minute and gestational age of 40 weeks was derived: PEP140,40 = PEP + 0.36(FHR-140) + 1.4(40-GA). PEP140,40 for our control group was 72.9 +/- 2.8 msec. Of the 13 fetuses classified as abnormal in the study, four had a normal PEP140,40 eight showed significant shortening, and one had significant prolongation. These changes in PEP were related to underlying fetal status, and, when used together with other parameters of antenatal assessment, appear to be useful in predicting the ability of the fetus to withstand stress compatible with survival. Continuing evaluation on larger populations will be required to confirm the results of this study. The use of PEP140,40 is suggested as a valid method for comparing reports from different investigators.