Increase In Fetal Heart Rate Research Articles

Effect of parasympathetic and beta-adrenergic blockade on the umbilical circulation in the unanesthetized fetal sheep.

Parasympathetic and beta-adrenergic blocking agents were administered to near term chronically instrumented sheep. Parasympathetic blockade resulted in a significant increase in fetal heart rate and fetal arterial blood pressure, with a minimal nonsignificant increase in umbilical blood flow. beta-Adrenergic blockade resulted in a decrease in fetal heart rate and umbilical blood flow, though neither was statistically significant. There was no change in arterial blood pressure. The net result of parasympathetic and beta-adrenergic blockade on fetal heart rate suggests that the intrinsic rate is the same as when these influences are present.

Cardiac output and its distribution and organ blood flow in the fetal lamb during ritodrine administration

The response of the fetal circulation to beta adrenergic stimulation with ritodrine hydrochloride has been investigated by long-term monitoring of the fetal lamb in utero. Ritodrine was infused intravenously either into the ewe or directly into the fetus, and cardiovascular and acid-base responses were measured. Fetal cardiac output and its distribution were measured with the use of radionuclide-labeled microspheres. The output of each ventricle also was measured by means of long-standing implanted electromagnetic flow transducers around the ascending aorta or pulmonary trunk during infusion of ritodrine at various rates into the fetus. Infusion of ritodrine (1.9 mcg. per kilogram per minute) into the ewe caused no change in fetal heart rate, blood pressure, cardiac output, or umbilical blood flow, but did cause an increase in fetal adrenal and myocardial blood flow. Ritodrine infused directly into the fetus produced a marked increase in fetal heart rate and a minimal change in cardiac output. There were no significant changes in fetal or maternal acid-base balance during the ritodrine infusions.

Studies of maternal-fetal interaction during the last trimester of pregnancy: Ontogenesis of the basic rest-activity cycle

The objective of this study was to identify and quantify fetal and maternal heart rate (FHR, MHR) periodicities and to examine their interrelation as well as the relation of fetal cycles with the maternal REM-NREM sleep cycle. Heart rate periodicities of the same subjects after birth were correlated with the neonatal REM-NREM sleep cycle. Sixteen all-night polygraphic recordings were obtained during the last trimester of pregnancy and the 1st week of life in seven subjects. Abdominal leads were used to obtain continuous fetal heart rates. Maternal and infant sleep states were scored according to standard criteria. Minute-by-minute values for maternal, fetal, and neonatal heart rates were analyzed on a PDP-12 computer and subjected to time series analyses including auto spectral techniques and complex demodulation. Period lengths of less than 1 h, between 1 and 2 h, and even longer were present in the tracings of mother, fetus, and neonate. Predictable interaction between maternal and fetal heart rate periodicities could not be established. None of the fetal rhythms bore a consistent relationship with the maternal REM-NREM sleep cycles. Maternal sleep onset or the first sleep cycle was accompanied by an increase in fetal heart rate lasting between 10 and 20 min in six of the nine recordings. Fetal heart rate cycles between 1 and 2 hr are probably early manifestations of the neonatal REM-NREM sleep cycle. The transient rise in fetal heart rate could be an adaptive response to either the fall in blood pressure or the shift in acid-base balance upon maternal sleep onset to which the fetus habituates within a short time.

Human fetal respiratory arrhythmia

The association of human fetal respiration with the fetal heart rate was studied in 13 pregnant patients between Weeks 34 and 41 of pregnancy. Fetal respiration was recorded with the use of a tocodynamometer. Fetal heart rate was recorded with the use of ultrasound and abdominal fetal electrocardiogram monitoring devices. The results documented the presence of human fetal respiratory arrhythmia. An increase in fetal heart rate was seen during fetal “inspiration” followed by a decrease during “expiration.” The possible mechanisms of the respiratory arrhythmia are discussed.

THE EFFECT OF MATERNAL EXERCISE ON FETAL HEART RATE AND SOME BIOCHEMICAL TEST REFLECTING FETOPLACENTAL FUNCTION

Six healthy women in the last trimester of pregnancy were exposed to long term, strenous exercise on an ergometer bicycle. Before, during and after the exercise their heart rate, blood pressure, and respiration rate were continuously recorded and repeated samples of venous blood obtained. Fetal heart rate was monitored using an ultrasound instrument. In most cases a significant increase in fetal heart rate was recorded during maternal exercise but different patterns of change in fetal heart rate were observed. Also the levels of progesterone, estradiol, estriol and chorionic somatotropin in maternal plasma varied during maternal exercise. The different patterns of changes in fetal heart rate and in the biochemical tests will be discussed.

Fetal responses to maternal exercise in the sheep

Fetal responses to maternal exercise were studied in twelve long-term sheep preparations. After hysterotomy, a polyvinyl catheter was inserted into the fetal aorta via the femoral artery (11 fetuses) or via a ligated umbilical artery (4 fetuses) and exteriorized. Seven to ten days later, the ewes were exercised on a treadmill (2.0 to 2.5 miles per hour) for 30 to 60 min. Maternal and fetal arterial pressures, heart rates, and blood pH, Po2, and Pco2 were monitored before exercise, at the end of exercise, and after a 30 min. recovery period. The results indicate that fetal responses to maternal exercise generally follow those of the mother. A significant increase in fetal pH and decrease in fetal Pco2 were observed at the end of exercise, and these were associated with maternal hyperventilation and respiratory alkalosis. Moreover, a significant reduction in fetal Po2 was noted with maternal exercise. A moderate increase in fetal heart rate was also observed with insignificant change in mean arterial blood pressure. The responses were similar in both fetuses with intact umbilical circulation and those with a ligated umbilical artery. However, the latter fetuses had a lower pre-exercise Po2 level and had greater decreases of oxygen tension with maternal exercise. The observed changes were reversible after 30 min. of recovery. These observations suggest that moderately severe maternal exercise may be detrimental to fetuses with some compromise of the umbilical circulation but that the normal fetus tolerates maternal exercise well. It is suggested that the decrease in fetal Po2 is due primarily to reduction in uterine flow during exercise and partially to changes of the oxygen affinities of maternal and fetal hemoglobins consequent to respiratory alkalosis.

The effect of cigaret smoking during pregnancy upon the fetal heart rate

A study of fetal heart rate before and after maternal smoking has been made a total of 81 times on 5 patients. The object of the study has been to determine the effect, if any, of maternal smoking on fetal heart rate. It was felt that if fetal heart rate was altered by maternal smoking, this change would indicate that the toxic products of tobacco smoke do pass through the human placenta and enter the fetal circulation. The results of the observations are as follows: 1.1. The average fetal heart rate for five minutes before smoking was 144.0 ± 0.14. The average fetal heart rate for the eighth to the twelfth minute after a cigaret was lighted and smoking begun, was 149.0 ± 0.13. The average increase in the rate was 5.0 ± 0.19 beats. Since the difference in rates before and after smoking is more than 25 times the probable error of the difference, the effect of smoking is actual.2.2. Of the 5 patients, 4 showed an increase in fetal heart rate after smoking, while the fifth showed a decrease. The 4 showing increases were habitual smokers who inhaled the smoke. The patient showing decrease had never smoked before, did not inhale, and expelled the smoke from her mouth as quickly as possible.3.3. There were occasional negative trials in each of the 4 patients showing increase. These occurred for the most part at times when the fetal heart rate during the control period was above its average.