Numeric analysis of heart rate variation in intrauterine growth-retarded fetuses: a longitudinal study

OBJECTIVE: We attempted to determine changes occurring with time in fetal heart rate and its variation in fetuses with intrauterine growth retardation in whom late antepartum fetal heart rate decelerations eventually develop. STUDY DESIGN: Thirteen fetuses with intrauterine growth retardation were studied over a median period of 25 days. One-hour fetal heart rate records were made two to five times per week and were analyzed numerically. Fetal movements were recorded by the women. RESULTS: On average long-term fetal heart rate variation decreased gradually with time and fell below the norm (30 milliseconds) at about the same time decelerations appeared. Mean heart rate showed a slight but statistically significant increase after the occurrence of decelerations. There were large interfetal differences in all parameters studied. CONCLUSION: In fetuses with intrauterine growth retardation a decrease in long-term fetal heart rate variation is a rather late sign of impairment that coincides with the occurrence of late decelerations. In the surveillance of the fetus with intrauterine growth retardation it might be most appropriate to use each fetus as its own control. (Am J Obstet Gynecol 1992; 166: 22-7.)