Long-term Fetal Heart Rate Research Articles

Effect of Oxymorphone Hydrochloride on Ovine Fetal Heart Rate Variability

In order to determine the effect of the narcotic analgesic oxymorphone hydrochloride (Numorphan, DuPont) on fetal heart rate (FHR) variability, mathematical indices of short-term and long-term FHR variability were determined continuously from R–R intervals of the electrocardiogram in eight chronically instrumented ovine fetuses for 60 min before and after a maternal intravenous bolus of 0.04 mg/kg oxymorphone. The index of short-term variability decreased from 12.7 ± 2.0 during control to 9.7 ± 1.7 during the period from 10 to 30 min after oxymorphone administration during periods of low-voltage, high-frequency electrocortical activity (LVHF ECoG) (P < 0.05). Mean FHR was decreased from 169 ± 8 beats per minute (bpm) during control to 155 ± 7 bpm 30 to 50 min after oxymorphone (P < 0.05). Fetal electrocortical activity was also determined and the decrease in FHR short-term variability occurred despite an increase in the percent time spent in LVHF electrocortical activity from 53 ± 4% during the control pe...

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

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. 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. 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. 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.

Human fetal behavioral states after vibratory stimulation

A total of 14 healthy pregnant women between 37 and 41 weeks' gestational age were studied to determine the effects of a 5-second external vibratory stimulus (100 Hz, square wave) on human fetal behavioral states. Fetal behavioral state observations were made with simultaneous recordings of fetal heart rate, gross fetal body movements, and fetal eye movement between 8:30 am and 4:00 pm . During the first episode of behavioral state 1 F (quiet sleep state) ≥ 10 minutes duration on two consecutive half days, the vibratory stimulus was placed on the surface of the maternal abdomen over the fetal head. Each fetus received one 5-second vibratory stimulus during either the first or second half day of observation. The time at which the instrument was applied but no vibratory stimulus was administered was considered as the control period. All women were then observed for 2 hours after the control period and after stimulation. A transition period from a quiet sleep state to a stable active sleep state (state 2F, rapid eye movement sleep) averaged ≤ 53 minutes after stimulation, as compared with 23 minutes after the control period. These changes in fetal behavioral states persisted for 20 minutes after vibratory stimulation. There also was an immediate and sustained increase in long-term fetal heart rate variability, the number of fetal heart rate accelerations and gross fetal body movement during the first 20 minutes after stimulus, without changes in basal fetal heart rate. We hypothesize that changes in fetal behavior seen after application of low frequency vibratory stimulus are more physiologic than the profound changes in fetal heart rate and gross fetal body movement previously described after vibratory acoustic stimulation with an electronic artificial larynx.

Human fetal behavioral states after vibratory stimulation

A total of 14 healthy pregnant women between 37 and 41 weeks' gestational age were studied to determine the effects of a 5-second external vibratory stimulus (100 Hz, square wave) on human fetal behavioral states. Fetal behavioral state observations were made with simultaneous recordings of fetal heart rate, gross fetal body movements, and fetal eye movement between 8:30 AM and 4:00 PM. During the first episode of behavioral state 1F (quiet sleep state) greater than or equal to 10 minutes duration on two consecutive half days, the vibratory stimulus was placed on the surface of the maternal abdomen over the fetal head. Each fetus received one 5-second vibratory stimulus during either the first or second half day of observation. The time at which the instrument was applied but no vibratory stimulus was administered was considered as the control period. All women were then observed for 2 hours after the control period and after stimulation. A transition period from a quiet sleep state to a stable active sleep state (state 2F, rapid eye movement sleep) averaged less than or equal to 3 minutes after stimulation, as compared with 23 minutes after the control period. These changes in fetal behavioral states persisted for 20 minutes after vibratory stimulation. There also was an immediate and sustained increase in long-term fetal heart rate variability, the number of fetal heart rate accelerations and gross fetal body movement during the first 20 minutes after stimulus, without changes in basal fetal heart rate. We hypothesize that changes in fetal behavior seen after application of low frequency vibratory stimulus are more physiologic than the profound changes in fetal heart rate and gross fetal body movement previously described after vibratory acoustic stimulation with an electronic artificial larynx.

Vibratory acoustic stimulation in 26- to 32-week, small-for-gestational-age fetus

Seven pregnant women with early-onset (less than 32 weeks' gestation) intrauterine growth retardation were studied to examine fetal heart rate and fetal activity patterns after vibratory acoustic stimulation. All studies were done between 26 and 32 weeks' gestation. All fetuses but one were not acidotic at birth. There was a reduced time during which accelerations (50% less), long-term fetal heart rate variability (25% less), and body movements (60% less) occurred in small-for-gestational-age fetuses compared with these times in age-matched normally grown fetuses. Fetal heart rate and fetal activity patterns were not significantly altered after stimulation with the electronic artificial larynx. We hypothesized that severe, early-onset (less than 32 weeks' gestation), chronic nutritional deprivation of human fetuses is associated with a delay in the functional maturation of fetal sensory receptors.

Fetal heart rate and activity patterns in growth-retarded fetuses: Changes after vibratory acoustic stimulation

Seventeen pregnant women who subsequently were delivered of infants with birth weights less than the third percentile were studied for examination of fetal heart rate and fetal activity patterns before and after a 5-second external vibratory acoustic stimulation. None of the fetuses was acidotic at birth. A reduced time was noted during which accelerations in heart rate occurred (50% less) and long-term fetal heart rate variability (25% less) in small for gestational age fetuses compared with age-matched, normally grown fetuses. The incidence of gross fetal body movements was significantly lower (40% less) in small for gestational age fetuses than in those who were appropriate for gestational age. Fetal heart rate and fetal activity patterns after stimulation with the electronic artificial larynx in small for gestational age fetuses were similar to those of appropriate for gestational age fetuses.

Fetal heart rate and fetal activity patterns after vibratory acoustic stimulation at thirty to thirty-two weeks' gestational age

Twenty pregnant women between 30 and 32 weeks' gestational age were studied to examine the effects of a 5-second external vibratory acoustic stimulus on the fetal heart rate, fetal heart rate variability, and fetal activity patterns. There was an immediate significant increase in the basal fetal heart rate for 10 minutes compared with controls. There was also a significant increase in the mean duration of fetal heart rate accelerations without any change in the number of fetal heart rate accelerations. There were no changes in long-term fetal heart rate variability, fetal breathing, and gross fetal body movements.

Patterns of human fetal heart rate accelerations from 26 weeks to term

Computerized analysis of the distribution of 2598 fetal heart rate accelerations in 83 healthy fetuses at 26 to 40 weeks' gestation demonstrated that the currently used definition of an acceleration as greater than or equal to 15 beats/min for greater than or equal to 15 seconds is applicable only after 30 weeks' gestational age in fetuses with a basal fetal heart rate of less than or equal to 128 beats/min. A significant negative correlation was found between the mean hourly basal fetal heart rate and the mean amplitude of fetal heart rate accelerations from 30 weeks to term. There was also a significant maturational process in the pattern of fetal heart rate and fetal heart rate accelerations that occurred between 26 and 28 and between 30 and 32 weeks; this was characterized by a decrease in basal fetal heart rate, an increase in the amplitude of fetal heart rate accelerations, and an increase in long-term fetal heart rate variability.

The change in fetal activity periods in diabetic and nondiabetic pregnancies

Fetal active and quiet periods of behavioral activity were determined at 28 to 32 weeks' and 36 to 40 weeks' gestational age in insulin-dependent diabetic pregnancies and in normal pregnancies resulting in infants with weights appropriate for gestational age. Fetal active and quiet periods were based on observations of fetal movements and long-term fetal heart rate variability. The number of fetal active-quiet periods, the average duration of fetal quiet periods, and the average duration of fetal active periods were the three parameters evaluated. In the normal pregnancy groups, with increasing fetal gestational age from 28 to 32 weeks to 36 to 40 weeks there was an increase in the length of the active and quiet periods with fewer active-quiet cycles per hour. The fetuses of the diabetic women had findings similar to those of the normal group at 28 to 32 weeks; these findings were essentially unchanged at 36 to 40 weeks. These findings suggest delayed development of the active-quiet cycles in these diabetic pregnancies.

Effect of acute hypoxemia and respiratory acidosis on the fetal heart rate in monkeys

The fetal heart rate (FHR) response to acute nonacidemic hypoxemia and to acute respiratory acidosis was studied in unanesthetized pregnant monkeys by means of chronically implanted catheters and electrodes. Average FHR and short- and long-term FHR variability were analyzed separately. The FHR response to either hypoxemia or hypercapnia consisted of slowing and increased variability. The slowing was more consistent with hypercapnia than with hypoxemia. Long-term FHR variability increased with both test stresses. The increase in short-term FHR variability was much greater in response to hypoxemia than to hypercapnia. Both the FHR slowing and the increases in variability in response to the test stresses were reduced by prior administration of atropine to the fetus.

Studies of antepartum behavioral state in the human fetus at term

This prospective study describes intrauterine behavioral states in the human fetus. The variables used are fetal movement and two expressions of fetal heart rate (FHR): long-term variability and baseline rate. Fetal movement was recorded with the use of two strain gauges. FHR was measured with a transabdominal fetal electrocardiographic processor. Sixteen fetuses of normal pregnant patients were studied near term. One-minute periods called “epochs” were classified as quiet, active, and intermediate, based on the presence or absence of fetal movement (longer in duration than one second), increased or decreased long-term FHR variability, and the baseline of the FHR. Complete agreement in epoch classification was noted in 79.3 per cent of the 2,054 epochs analyzed. Quiet and active one-minute epochs were clustered into longer time periods representing quiet and active fetal behavior states similar to those seen in the neonate. The overall visual evaluation of the tracings based on the above noted criteria demonstrated the presence of quiet, active, and transitional states in the fetus. Mean duration of a complete cycle, including the quiet, active, and transitional states, was 62.3 minutes. The mean duration in the quiet state was 22.8 minutes and the mean duration in the nonquiet states (active and transitional) was 39.5 minutes. The significance of these intrauterine behavioral states is stressed.