Heart rate in fetuses and neonates in normal conditions and with mild depression

The continuous recording of fetal and neonatal heart rate gives reliable information on the condition of the fetus and neonate. In the present study the results obtained in vigorous and mildly depressed newborns, by the continuous recording of fetal heart rate during labor and of neonatal heart rate during 90 minutes after birth, are presented. Twenty three pregnant women were studied during labor, as well as their newborns. They fulfilled the following conditions: --Mothers without known complications and good prenatal care. --Term pregnancies with single fetuses in vertex presentation with birthweight normal for age. --All labors started, progressed and delivered spontanously withoug signs of fetal distress. No drugs were given to the mother during labor or to the neonate. The umbilical cord was clamped immediately after birth. Seventeen neonates were vigorous at 1 and 5 minutes (Apgar score 7 or higher). Six neonates were slightly depressed at the first minute but all of them recovered at 5 minutes. Both groups are studied separately. Figure 1 shows the average values of BFHR and NHR corresponding to 17 vigorous newborns (Apgar scores 7-10 at the first and fifth minutes of life). No major variations were found in the average values of BFHR in the time period studied. No statistically significant differences were found in the BFHR of the same fetus at 60, 30 and 8 minutes before delivery (Fig. 2). A decrease in BFHR occurred during the 6 minutes preceding birth (fig. 1). After birth the average values of NHR were higher than the fetal ones (Fig. 1). This post-natal increase in heart rate (32 beats/min) is statistically significant when BFHR values 30 minutes before delivery are compared with NHR values recorded 10 minutes after birth (Fig. 3). After this initial increase, NHR starts a gradual fall, lasting about 50 minutes and then becomes stable at a level similar to that of fetal heart rate (Fig. 1). Figure 1 shows that puncture of the heel causes an increase in NHR. The difference between NHR before and after the puncture is significant (Fig. 6). The heart rate of 6 newborns which were slightly depressed at the first minute of life (Apgar score 4-6) but vigorous at the fifth minute, are not significantly different from those of the vigorous group of 17 neonates (Fig.7). The cases chosen for this study have been carefully selected with the aim of establishing the "normal" pattern of fetal and neonatal heart rate. We concluded that in normal term labors BFHR remains stable from 90 until 10 minutes before delivery; there is a tendency to fall during the last 6 minutes preceeding birth. Immediately after birth, neonatal heart rate rises significantly, then falls gradually and becomes stabilized 50 minutes after delivery, at levels similar to those of BFHR.