Fetal heart rate responses to maternal exercise

The fetal heart rate responses to mild, moderate, and strenuous maternal exercise were studied in 45 healthy subjects. In the majority of cases, the fetal heart rate increased during and after maternal exercise. Fetal bradycardia was recorded in five fetuses; this appears to be a sporadic event. There was no correlation between the individual fetal heart responses, gestational age, exercise intensity, and maternal circulating catecholamines.     

Fetal and maternal Doppler velocimetry and cytokines in high-risk pregnancy

OBJECTIVE: Fetal hypoxia and preterm delivery are reported to be strongly associated with brain damage and neurodevelopmental delay. Doppler signs of fetal brain sparing have been described during chronic hypoxia, but whether they are related to brain damage is unknown. The aim of this study was to evaluate if markers of tissue injury, i.e., tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) are related to signs of increased perinatal vascular impedance and/or fetal brain sparing in high-risk pregnancies. STUDY DESIGN: TNF-alpha and IL-6 levels were evaluated in maternal blood serum of 67 high-risk pregnancies. Serum samples were taken at the time of umbilical, middle cerebral artery and uterine artery Doppler velocimetry examination. The values for TNF-a and IL-6 were correlated with reference median values obtained with gestational age in the form of a Z-score. RESULTS: TNF-alpha levels showed values within the normal range in only four cases. IL-6 values were found normal in 14 cases. The Z-score for mean middle cerebral artery pulsatility index (PI) showed a significant correlation to TNF-alpha and IL-6 levels, P < 0.0001 and P < 0.003, respectively. This might suggest a strong correlation between signs of fetal brain sparing and increased maternal serum TNF-alpha and IL-6 levels. Abnormal uterine artery PI and the presence of a "notch" were also highly significantly related to TNF-alpha and IL-6 levels, which were nearly two-fold higher compared to normal uterine artery blood flow and the absence of a "notch". Abnormal cerebro/placental ratios showed significant correlations to TNF-alpha and IL-6 levels. CONCLUSION: The present results suggest a strong correlation between levels of TNF-alpha and IL-6 not only for signs of fetal brain sparing, but also for uteroplacental blood flow. This finding supports the role of tissue injury in cases of fetal brain sparing, but whether this is a reflection of brain damage or secondary to placental pathology needs further evaluation.     

Fetal responses to maximal swimming and cycling exercise during pregnancy

Fetal responses to maximal maternal exercise were studied during cycle ergometry and tethered swimming in 13 untrained subjects at 25 and 35 weeks' gestation. The fetal heart rate (FHR) and uterine and umbilical artery waveforms were measured before exercise, immediately after exercise, and at 5-minute intervals during 20 minutes of recovery. The mean maternal maximal heart rate was 179 +/- 12 beats per minute and did not differ between swimming and cycling exercise trials. Six episodes of transient bradycardia occurred after a total of 45 maximal exercise trials. The mean FHR decreased slightly immediately after exercise, then increased approximately ten beats above baseline levels at 10-20 minutes after exercise (P less than .02). The changes from baseline in FHR were greater after cycling than after swimming. Changes observed in the systolic-diastolic ratio (S/D) of the umbilical artery could be accounted for by the FHR variations. The S/D of the uterine artery was significantly higher after cycling than after swimming (P = .05). We conclude that maximal maternal exercise during pregnancy causes transient fetal bradycardia in approximately 15% of cases, in cycling more often than in swimming.     

Fetal and maternal Doppler flow velocity waveforms in normal sheep pregnancy

Abnormalities in placental vascular resistance have been shown to have an important association with intrauterine growth retardation in both human and sheep pregnancies. In this study we have assessed impedance to blood flow through the ovine placental circulation by Doppler flow velocity waveform analysis. As gestation advanced from 66 to 136 days, a significant decrease in impedance to flow was observed in both umbilical and maternal placental arteries. The greatest decrease in impedance was observed between 66 and 109 days' gestation in umbilical arteries and between 66 and 80 days' gestation in maternal placental arteries. In these normal pregnancies, no significant correlations could be found between Doppler flow velocity waveform analyses and fetal or placental growth. We conclude that Doppler flow velocity waveform analysis is a valuable and non-invasive method to assess impedance to blood flow through the placental circulation in pregnant sheep.     

Fetal heart rate response to maternal exercise

Twenty-five pregnant women without complications underwent fetal heart rate evaluation during a program involving exercise at a relative intensity of 61% to 73% of maximal capacity during the course of the pregnancy. Assessment of the influence of gestational age on the fetal heart rate response to exercise and evaluation of the course of fetal heart rate recovery were the main goals of the study. The results of the study confirmed previous findings that fetal heart rate is accelerated after maternal exercise. However, contrary to other studies we found no effect of gestational age on the fetal heart rate response to exercise. Neonatal findings provided further evidence that quantitated maternal exercise up to 70% of maximal capacity does not interfere with normal fetal growth and development.     

A quantitative investigation of hemodynamic adaptation to pregnancy using uterine artery Doppler ultrasonography and finger photoplethysmography

Objective: Normal pregnancy is characterized by maternal hemodynamic adaptations of cardiovascular system and uterine artery. We aimed to investigate quantitatively the relationship between uterine artery Doppler (Ut AD) ultrasonography and finger photoplethysmography (PPG) in each of the three trimesters. Methods: Eighty normal pregnancy subjects were recruited from the nulliparous women with uncomplicated singleton pregnancy presenting for a routine ultrasound scan and divided into three groups according to their trimester. Comparative analysis were conducted between Ut AD ultrasonography and finger PPG within and across trimesters, particularly with focus on the relationship between Uterine Artery Resistance Index (UtA RI) and photoplethysmographic reflection index (PPG RI) throughout pregnancy. Additional 10 preeclampsia patients in third trimester were enrolled for comparison. Results: Both UtA RI and PPG RI were markedly decreased with gestation in normal pregnancy and generally consistent with each other in trend. The preeclampsia patients of third trimester were significantly higher in both indices, even more than normal pregnancy subjects of first trimester. Conclusions: The results of this study revealed clear relationship between UtA RI and PPG RI throughout pregnancy which could be exploited to enhance the potential ability in early recognition of pathophysiologic process in maternal adaptation and prediction of complicated pregnancy.     

Fetal hemodynamic response to maternal intravenous nicotine administration.

OBJECTIVES: Our study was designed to test the hypothesis that maternally administered nicotine has significant effects on fetal hemodynamics and umbilical systolic/diastolic ratios. STUDY DESIGN: Nine pregnant ewes received maternal intravenous infusions of 10, 20, and 30 micrograms/kg/min of nicotine. Maternal and fetal blood pressure, heart rate, and uterine and umbilical blood flow were recorded. RESULTS: Maternal intravenous administration of nicotine (10, 20, and 30 micrograms/kg/min of maternal body weight) produced significant (p < 0.05) increases in fetal blood pressure (2%, 11%, and 25%, respectively), decreases in fetal heart rate (0%, 8%, and 12%), and decreases in umbilical blood flow (0%, 0%, and 19%). Umbilical systolic/diastolic ratios increased slightly at the 30 micrograms/kg/min dose of nicotine, but these changes did not reach significance. Maternal blood pressure increased (10%, 25%, and 53%), and uterine vascular resistance increased (5%, 64%, and 344%) significantly (p < 0.05); uterine blood flow increased at the 10 micrograms/kg/min dose (+5%) and decreased by 23% and 42% at the highest two doses of nicotine. CONCLUSION: Maternal nicotine administration in late-term pregnant sheep produced significant increases in fetal arterial blood pressure and umbilical vascular resistance, decreased fetal heart rate, and umbilical blood flow but did not significantly alter systolic/diastolic ratios.     

Fetal circulatory responses to maternal blood loss

We examined the fetal circulatory responses to maternal blood loss in pregnant women during the third trimester. Seven healthy women with placenta previa and singleton pregnancies underwent phlebotomies in an autologous donation program. Four hundred milliliters of blood was collected within 15 min at 34 and 35 weeks of gestation. Continuous electric recordings of fetal heart rate were performed during the first blood collection, and the maternal uterine artery (UtA), umbilical artery (UmA) and fetal middle cerebral artery (MCA) Doppler velocity waveforms were recorded before, immediately after and 24 h after the second collection in each patient. The average fetal heart rate, maternal UtA and UmA pulsatility indices did not change measurably during or after maternal blood collections. However, the average fetal MCA pulsatility index decreased significantly 24 h after maternal blood loss. The observation of a decrease in fetal MCA pulsatility index may indicate delayed fetal asphyxia following mild maternal hemorrhage.     

Fetal heart function in response to short-term maternal exercise

Fetal cardiac reactions to maternal exercise were studied in the fetuses of 22 healthy pregnant women between 18 and 36 weeks of gestation. Before and 5 min after a bicycle ergometer load test of 75 W each fetus was studied with M-mode echocardiography. Fetal cardiac dimensions, ventricular ejection times and heart rate were recorded and indices of left ventricular heart function (fractional shortening, mean velocity of fractional shortening, stroke volume and cardiac output) were calculated. While median maternal heart rate acceleration reached 68% of expected maximum heart rate, no significant alterations in fetal heart rate, fetal cardiac dimensions or fetal ventricular function were observed. The results indicate that short-term moderate maternal exercise can be performed without fetal cardiac distress.     

Fetal and uterine responses to immersion and exercise

We evaluated the responses of the fetal-maternal unit to immersion and exercise in the water at 15, 25, and 35 weeks' gestation. As seen by underwater ultrasound, fetuses demonstrated body, limb, and breathing movements. Fetal heart rates (FHRs) were normal, and unchanged from those at rest, during maternal exercise in the water at 60% VO2 maximum. In 21 of 23 cases, post-exercise nonstress tests were reactive within ten minutes. There was no uterine activity seen at either 25 or 35 weeks' gestation. Maternal serum alpha-fetoprotein was unaffected at all gestational ages. Neither maternal temperature nor calculated plasma volume changed during exercise. This general lack of effect contrasts with results from other studies involving similar levels of exercise on land. We speculate that the plasma volume expansion with immersion contributes to the normal FHR responses seen in this study.     

Fetal and maternal adrenals in human pregnancy

Human pregnancy is marked by alterations in several endocrine systems--perhaps most notably, the striking increase in steroid hormone production by the adrenals of the fetus and mother. Morphologically and physiologically, the human fetal adrenal glands are remarkable organs. In proportion to the adult organs, the adrenal cortex is the largest organ of the fetus. At term, they produce more steroid and weigh the same as adrenal glands of the adult. Much of the steroid that is released by the fetal and maternal adrenals during pregnancy is the sulfated form of dehydroepiandrosterone (DHEA-S), which is used by the placenta to produce estrogens. Herein, we discuss the physiologic and pathophysiologic hormonal changes of the fetal and maternal adrenals during the course of pregnancy.     

Pulmonary responses to exercise in pregnancy

The pulmonary responses of 88 pregnant women were compared to those of 39 nonpregnant control subjects during different exercise intensities. At rest the pregnant women had higher tidal volumes, oxygen consumption, carbon dioxide production, and respiratory exchange ratio. With increased work loads the pregnant volunteers have consistently lagged behind the nonpregnant control subjects for every parameter, which indicates a decrease in pulmonary reserve and inability to exercise anaerobically.     

Fetal extremity kinetics quantified with Doppler ultrasonography

AIMS: To assess the responsive fetal extremity movement to vibro-acoustic stimulation test (VAST). METHODS: The moving velocity of fetal femur was assessed after VAST by pulsed Doppler device. The ultrasonic beam was insonated at a right angle to the fetal femur. The following parameters were determined: limb retreat velocity in accelerative slope (Pk1); limb replenishment velocity in decelerative slope (Pk2); mean flexion to extension velocity; and the response time to VAST. Among 80 normal singleton pregnancies in 33-41 weeks, 68 were weekly evaluated and the others were assessed for two or more times during the study period, for a total of 680 studies of fetal kinetics. RESULTS: The Pk1 declined from 9.6 to 6.26 cm/s; Pk2 decreased from 2.6 to 1.3 cm/s; mean velocity was reduced from 6.0 to 4.25 cm/s; whereas the response time increased from 0.1 to 0.3 s throughout the study period, i.e., fetal response reduces and the response time increases as maturation progresses. CONCLUSION: The pulsed Doppler may assess fetal activity in any body structure. Reflex responses become slow and complex on both the velocity and response time as maturation increases with gestational age. Our observations have resulted in a novel and easy method for the quantitative assessment of fetal reflex reactivity to external stimuli.     

Fetal breathing movements and maternal exercise.

Earlier statements that fetal breathing movements (FBM) are sensitive to changes in the fetal homeostasis prompted the study of the effect of maternal exercise on FBM and fetal heart rate. Forty women in the last trimester of gestation were subjected to a work load (80 W) for 5 min on a bed ergometer cycle; in 30 of them FBM were recorded by A-mode ultrasound, and in 10, the fetal heart rate was monitored by continuous ultrasound. Maternal blood pressure, pulse rate, blood pH and pCO2, and transcutaneous pO2 were also followed. The FBM showed a transient marked increase in incidence immediately after the end of the exercise. No changes in basal level or in baseline variability of the fetal heart rate were found in the recovery period after work. Some possible causes of the observed FBM alterations are discussed. The findings imply that, after this particular form of stress, FBM are a more sensitive indicator of the physiological state of the fetus than the fetal heart rate.     

Fetal responses to maternal infusions of angiotensin II

It is unclear whether the fetus is affected by maternal infusions of angiotensin II; therefore we studied maternal and fetal responses (n = 9) to angiotensin II (1.15, 2.29, 11.5 micrograms/min) infused 5 minutes into the vena cava of chronically instrumented sheep (129 to 137 days of gestation) while monitoring PO2, PCO2, pH, heart rate, uterine blood flow, and arterial and umbilical venous pressures. Pregnant sheep demonstrated expected dose-related increases in mean arterial pressure and decreases in uterine blood flow (p less than 0.05). Increases in fetal mean arterial pressure also correlated with the maternal dose of angiotensin II (r = 0.77, p less than 0.001). Fetal heart rate appeared to increase with 2.29 micrograms/min; however, bradycardia was observed with 11.5 micrograms/min (p less than 0.05) and was associated with decreased PaO2, 19.0 +/- 1.0 to 14.3 +/- 1.4 mm Hg (p less than 0.05), increased PaO2 (p less than 0.05), and decreased umbilical venous PO2, 31.4 +/- 2.3 to 27.0 +/- 1.9 mm Hg. The decreases in PO2 correlated with decreases in uterine blood flow (r = 0.60, p less than 0.002, and r = 0.75, p less than 0.005, respectively). Nevertheless, changes in fetal mean arterial pressure also occurred in the absence of altered fetal oxygenation; thus decreased uterine blood flow and fetal oxygenation alone cannot explain the fetal cardiovascular responses. It is suggested that angiotensin II or an active metabolite may cross the ovine placenta.     

Renal responses to immersion and exercise in pregnancy

Twelve healthy pregnant women were studied at 15, 25, and 35 weeks' gestation and at 8 to 12 weeks postpartum. Women were immersed for 20 minutes at 30 degrees C. They then exercised at 60% maximum oxygen capacity on a modified ergometer. Substantial diuresis and natriuresis occurred without changes in osmolarity or serum sodium. The diuresis was significantly greater during pregnancy than postpartum. The natriuresis was similar. Diuresis and natriuresis were greater than would be expected from investigations in nonpregnant subjects. This study suggests that immersion may be a beneficial therapy for edema without decreasing plasma volume.     

Fetal and maternal leptin in pre-gestational diabetic pregnancy

ObjectiveTo compare maternal and fetal leptin among women without diabetes, women with type 1 diabetes, and women with type 2 diabetes.MethodsIn a prospective study at the National Maternity Hospital, Dublin, 40 women with type 1 diabetes, 10 with type 2 diabetes, and 30 without diabetes were enrolled between July 2006 and July 2008. Maternal (36-week) and cord blood leptin was measured by enzyme-linked immunoassay.ResultsNo difference was found in maternal leptin among the groups: without diabetes (mean, range): 325 pg/mL, 36–1492 pg/mL; type 1 diabetes: 343.2 pg/mL, 55.5–1108.2 pg/mL; type 2 diabetes: 202.2 pg/mL, 35.1–1553.3 pg/mL (P > 0.05). Leptin levels were higher among fetuses of women with type 1 (223 pg/mL, 25.7–810 pg/mL) and type 2 (447.2 pg/mL, 136.3–679 pg/mL) diabetes than among women without diabetes (80.3 pg/mL, 27.3–623.1 pg/mL; P < 0.05). The single significant predictor of fetal leptin for the whole cohort was maternal body mass index (BMI; r = 0.39, P = 0.01). Only third-trimester glycosylated hemoglobin (HbA1c) was significantly related to fetal leptin after controlling for maternal BMI among women with diabetes (r = 0.28, P = 0.04).ConclusionFetuses of women with diabetes might have some degree of leptin resistance. This might be important in appetite regulation in extrauterine life.