To analyze the effect of hypoxaemia on heart rate variability (HRV) in fetal lambs by means of power spectrum, the intrauterine surgical operations were performed at 116-125 gestational days in 7 lambs. Arterial catheter was inserted in the fetal femoral artery and sent to aorta abdominalis, and blood pressure was recorded continually on tape recorder. The microspheres were injected via the arterial catheter to block the micrangium of placenta, thus making an animal model of fetal hypoxaemia. The fetal blood sample was drawn through the catheter for blood gas analysis. In terms of the heart beat variability power spectral density, there were four consistent components, namely very low (VL, 0.01-0.025 cycle/beat), low (L, 0.025-0.125 cycle/beat), middle (M, 0.125-0.2 cycle/beat), and high (H, 0.2-0.5 cycle/beat). Integrated peaks in the power spectrum were compared before and after administration of microsphere. The spectral power in the L frequency components was significantly increased (0.07 +/- 0.01 vs. 0.21 +/- 0.03, P<0.01), and the spectral power in the H frequency components was significantly reduced (0.53 +/- 0.1 vs. 0.27 +/- 0.05, P<0.05). There was no significant difference in M and VL. The times of microsphere injection were related to fetal blood pH (r=0.585, p<0.01), PCO2 (r=0.5, p<0.05) and PO2 (r=0.75, P<0.01). The results clearly demonstrate the association between change of power spectrum of heart rate variability and the effect of hypoxia of the fetus in labour.
Animals ; Blood Gas Analysis ; Female ; Fetal Blood ; Fetal Hypoxia ; physiopathology ; Fetal Monitoring ; Heart Rate, Fetal ; physiology ; Pregnancy ; Sheep

Background : The approximate entropy of heart rate variability has recently been used as a tool in evaluating cardiovascular health and physiology and in diagnosing pertubated physiologic status, by quantifying the irregularity and the pattern of the heart rate variability. Therefore approximate entropy of the fetal heart rate variability will be used as an important tool in studying the fetal cardiovascular health and disease, but unfortunately there have been no previous systematic studies of the approximate entropy in normal fetuses. This study's aim has been to present the normal approximate entropy values of the fetal heart rate variability according to the gestational age, to demonstrate the developmental maturation of physiology of the control systems of the heart rate, and to quantify the evolution of the pattern of fetal heart rate variability. METHODS: Three hundred and thirty seven mothers with normal singleton pregnancies, who were 20 weeks or more of gestational age, were randomly chosen. For more than 40 minutes fetal heart rates and fetal movements were recorded and were downloaded to a computer. From each heart rate data, 5000 points ('total') of heart rate during which fetal movements occured and 1200 points ('rest') during which no fetal movement occured were selected and the approximate entropy was calculated, and then 2 weeks' average of the approximated entropy of the heart rate were calculated and compared to find the maturational differences of them. RESULTS: The approximate entropy of the rest period showed a tendency to increase with advancing gestation (p=0.0001). It was significantly higher between the 41st-42nd week (0.987 +/-0.017) than the period before the 24 th week (0.864+/-0.032) and between the 25th-26th week (0.868+/-0.022). (p<0.05). The approximate entropy of the total period showed another tendency (p<0.05): from a low level before the 24 th week (0.788+/-0.067) it increased to reach its peak at the 29th-30 th week (0.963+/-0.041) then it gradually decreased again to significantly (p<0.05) lower levels at the 37th-38th week (0.776+/-0.046) and the 39th-40th week (0.786+/-0.047). CONCLUSIONS: Normal value of approximate entropy, which is bound to be used as an index in evaluating the fetal well-being, has been presented from 20th to 42th week of gestation with an interval of two weeks. The systems that control the heart rate seem to mature consistently as gestation advances, but before the 26th week it is significantly more immature than at term. Fetal heart rate variability evolves from an immature oscillating pattern into a transitional patternless pattern during the second trimester and finally consolidates into a mature accelerational pattern during the third trimester.
Entropy* ; Female ; Fetal Heart* ; Fetal Movement ; Fetus ; Gestational Age ; Heart Rate ; Heart Rate, Fetal* ; Humans ; Mothers ; Physiology ; Pregnancy ; Pregnancy Trimester, Second ; Pregnancy Trimester, Third ; Pregnancy* ; Reference Values

The purpose of this study was to investigate the feasibility of different fetal heart rate (FHR) ranges in the nonstress test (NST) and to better understand the meaning of mild bradycardia and/or tachycardia without non-reassuring patterns. We employed the heredity to show that mild bradycardia (100-119 beats per minute, bpm) and mild tachycardia (161-180 bpm) regressed to the normal FHR range (120-160 bpm). We used linear regression to analyze FHR data from FHR tracings recorded 10 min before (NST, as the predictor) and 10 min after vibroacoustic stimulation testing (as the dependent variable). Acceleration for 15 bpm-15 seconds (Acc1515) and deceleration for 15 bpm-15 seconds (Dec1515) in the NST were also analyzed for each group. The slope of the best-fit line was the largest in the mild bradycardia group and the smallest in the normal range group. Dec1515 was most prominent in mild tachycardia and both the mild bradycardia and tachycardia groups regressed towards the mean FHR range. Therefore, we propose that both mild bradycardia and tachycardia of FHR in non-acute situations (range between 100 and 180 bpm) are not regarded a pathologic signal for clinical use.
Acoustic Stimulation ; Bradycardia/physiopathology ; Female ; *Fetal Monitoring ; Heart Rate, Fetal/*physiology ; Humans ; Pregnancy ; Pregnancy Trimester, Third ; Regression Analysis ; Tachycardia/physiopathology

Various interference and noises should be eliminated while picking up the signal of fetal heart rate from the Doppler fetal signal in order to obtain smooth curve of the fetal heart Doppler signal and so to figure out the fetal heart rate. In this study, the mean frequency shift curve estimated from the Doppler fetal signals was smoothed using wavelet transform. The results showed that the fetal-heart rate obtained by computing from the autocorrelation waveform based on the smoothed mean frequency shift curve was more accurate than that based on unsmoothed curve.
Female ; Fetal Monitoring ; Heart Rate, Fetal ; physiology ; Humans ; Pregnancy ; Signal Processing, Computer-Assisted ; Ultrasonography, Doppler ; methods ; Ultrasonography, Prenatal

OBJECTIVEAlthough the only objective finding of intrapartum fetal distress is obtained through the measurement the fetal scalp pH, this invasive procedure is not available in every institution. The careful examination of fetal heart rate tracings for abnormalities, especially of the most commonly seen one, variable decelerations gains great importance under these circumstances. The aim of the present study is to determine the prognostic significance of variable decelerations in intrapartum fetal heart rate monitoring.

METHODSA total of 96 fetal heart rate tracings were analysed to assess the prognostic significance of variable decelerations. Sixty-six percent (64/96) of cases exhibited atypia characterised with (1) slow return of the fetal heart rate to the baseline; (2) loss of variability during the decelerations; (3) loss of initial and/or secondary accelerations; (4) persistence of secondary acceleration (overshoot); and (5) continuation of the baseline fetal heart rate at a lower level; (6) biphasic deceleration. One and five-minute Apgar scores and umbilical artery pH were used to assess the final fetal condition.

RESULTSAdverse fetal outcome characterised by fetal acidosis and Apgar score lower than 7 at one and five minutes were uncommon with pure variable decelerations. Typical and atypical variable decelerations were associated with low Apgar scores (< 7) at one minute in 9.3% and 54.6% of cases (p < 0.001) and at five minutes in 6.25% and 25% of cases (p < 0.05), respectively. In addition umbilical artery pH found to be lower than 7.2 in these cases ( 18.75% - p < 0.05). There was no danger for the fetal haemodynamic conditions when typical uterus contraction/variable deceleration ratios were two or more than two. However, risk of fetal hypoxia damage was quite high when this ratio was lower than two in atypical variable 5th minute low Apgar scores and pH (81.8% and 36.6% respectively). Atypical features are helpful in the identification of distress characterised by low Apgar scores in fetuses with variable decelerations. Admission to the neonatal intensive care unit was more common in patients with atypical variable decelerations in comparison with typical variable decelerations (34.3% versus 3.1%).

CONCLUSIONWhile typical variable decelerations are frequently harmless, atypical variations pose a significant risk of fetal hypoxia.

Acidosis ; Chi-Square Distribution ; Female ; Fetal Monitoring ; Heart Rate, Fetal ; physiology ; Humans ; Hydrogen-Ion Concentration ; Predictive Value of Tests ; Pregnancy ; Pregnancy Outcome ; Prognosis ; Uterine Contraction

The paper presents the development and design of an ultrasonic Doppler fetal heart rate monitoring system based on DSP, and explains the realization of a algorithm for detecting fetal heart rate. Clinical practice has proved that this system is able to pick up the real-time fetal heart rate correctly and rapidly.
Algorithms ; Fetal Monitoring ; instrumentation ; methods ; Heart Rate, Fetal ; physiology ; Humans ; Sensitivity and Specificity ; Signal Processing, Computer-Assisted ; Ultrasonography, Doppler ; instrumentation ; methods ; Ultrasonography, Prenatal ; instrumentation ; methods

OBJECTIVETo study the effects of dopamine and phenylephrine for treatment of hypotension during cesarean section under combined spinal epidural anesthesia (CSEA) on the stereology of the placenta.

METHODSForty puerperants undergoing cesarean section under CSEA were randomly divided into dopamine group and phenylephrine group. Ropivacaine (16 mg) was administered immediately after spinal anethesia. Blood pressure was maintained near the baseline by adjusting the drug infusion rate. Fetal blood gas, Apgar score, and placental villus microvascular stereological changes were observed during the operation.

RESULTSThe microvascular density was significantly lower in dopamine group than in phenylephrine group (P<0.05). Phenylephrine group showed significantly lower umbilical artery blood pH than dopamine group (P<0.05). The Apgar score and blood pressure were comparable between the two groups (P>0.05). Compared to the baseline, both of the two groups showed significantly lowered heart rate during the operation (P<0.01).

CONCLUSIONDopamine is associated with the risk of fetal acidosis. Phenylephrine is helpful for preventing hypotension by increasing placental blood flow and improving oxygen supply to ensure maternal and fetal safety during cesarean section.

Amides ; administration & dosage ; Anesthesia, Spinal ; Apgar Score ; Blood Gas Analysis ; Blood Pressure ; Cesarean Section ; Dopamine ; administration & dosage ; Female ; Fetal Blood ; Fetus ; Heart Rate ; Humans ; Hypotension ; drug therapy ; Infant, Newborn ; Oxygen ; Phenylephrine ; administration & dosage ; Placenta ; drug effects ; physiology ; Pregnancy ; Vasoconstrictor Agents ; administration & dosage