Doppler flow velocity waveforms in the embryonic chicken heart at developmental stages corresponding to 5-8 weeks of human gestation.

OBJECTIVES: To obtain Doppler velocity waveforms from the early embryonic chicken heart by means of ultrasound biomicroscopy and to compare these waveforms at different stages of embryonic development. METHODS: We collected cardiac waveforms using high-frequency Doppler ultrasound with a 55-MHz transducer at Hamburger-Hamilton (HH) stages 18, 21 and 23, which are comparable to humans at 5 to 8 weeks of gestation. Waveforms were obtained at the inflow tract, the primitive left ventricle, the primitive right ventricle and at the outflow tract in 10 different embryos per stage. M-mode recordings were collected to study opening and closure of the cushions. By exploring the temporal relationship between the waveforms, using a secondary Doppler device, cardiac cycle events were outlined. RESULTS: Our results demonstrate that stage- and location-dependent intracardiac blood flow velocity waveforms can be obtained in the chicken embryo. The blood flow profiles assessed at the four locations in the embryonic heart demonstrated an increase in peak velocity with advancing developmental stage. In the primitive ventricle the 'passive' (P) filling peak decreased whereas the 'active' (A) filling peak increased, resulting in a decrease in P to A ratio with advancing developmental stage. M-mode recordings demonstrated that the fractional closure time of the atrioventricular cushions increased from 20% at stage HH 18 to 60% at stage HH 23. CONCLUSION: High-frequency ultrasound biomicroscopy can be used to define flow velocity waveforms in the embryonic chicken heart. This may contribute to an understanding of Doppler signals derived from valveless embryonic human hearts at 5 to 8 weeks of gestation, prior to septation.

Blood pressure estimation in the human fetal descending aorta.

OBJECTIVES: The objectives of this study were to estimate fetal blood pressure non-invasively from two-dimensional color Doppler-derived aortic blood flow and diameter waveforms, and to compare the results with invasively derived human fetal blood pressures available from the literature. METHODS: Aortic pressures were calculated from digitally recorded color Doppler cineloops of the fetal descending aorta by applying the Womersley model in combination with the two-element Windkessel model, assuming constant pulse wave velocity during the second half of pregnancy. The results were compared with invasively derived human fetal blood pressures obtained from the literature. RESULTS: In 21 normal pregnancies the estimated mean aortic pressure regression line increased linearly from 28 mmHg at 20 weeks of gestation to 45 mmHg at 40 weeks of gestation. The pulse pressure based on the regression line increased linearly from 21 mmHg at 20 weeks of gestation to 29 mmHg at 40 weeks of gestation. The aortic compliance exhibited a log linear relationship with the gestational age and a statistically significant eightfold increase was observed between 20 and 40 weeks. The aortic downstream peripheral resistance exhibited an exponentially decaying relationship across the same gestational age range. Non-invasively derived aortic systolic and diastolic aortic pressures were comparable with previously reported invasively derived systolic and diastolic umbilical arterial pressures; however, the mean pressures differed significantly from those reported in the umbilical artery in a separate study. The aortic systolic pressures calculated in this study were significantly higher than invasively derived left ventricular systolic pressures that have been previously reported in the literature. CONCLUSIONS: This study demonstrates the feasibility of estimating arterial blood pressure in the human fetus. The method described is of potential use in assessing fetal blood pressure non-invasively, particularly for studying relative changes with time.

Evaluation of volume vascularization index and flow index: a phantom study.

OBJECTIVES: Three-dimensional (3D) power Doppler ultrasonography provides indices to quantify moving blood within a volume of interest (e.g. ovary, endometrium, tumor or placenta). The purpose of this study was to determine the influence of ultrasound instrument settings on vascularization index (VI) and flow index (FI) at different flow velocities, using a specially built flow phantom with a small tube diameter. METHODS: Blood-mimicking fluid was pumped at 10-100 mL/h through a plastic tube with a diameter of 0.65 mm within a virtual spherical volume (content 137.12 cm(3)) of a Voluson 730 Expert 3D power Doppler ultrasound instrument. VI and FI were determined at different pulse repetition frequency (PRF) settings, with minimal and maximal wall motion filter (WMF) settings. The measured VI was compared with the actual VI. RESULTS: The ability to measure VI and FI at different flow velocities was highly dependent on the PRF and WMF settings. In our experimental set-up, using a PRF of 0.3 kHz, flow velocities of about 2 cm/s and higher could be registered. Measured VI was overestimated up to 44 times relative to actual VI. CONCLUSIONS: Our main finding in a laboratory set-up was a considerable overestimation of moving blood volume using 3D power Doppler ultrasound in a single small tube. The degree of overestimation depends on the spatial resolution and on the settings of the ultrasound instrument. When small vessels are involved in a clinical setting, interpretation of VI should take this overestimation of moving blood volume into account.

Comparison between color Doppler cineloop- and conventional spectral Doppler-derived maximum velocity and flow in the umbilical vein.

OBJECTIVE: To compare the umbilical venous flow velocity derived from color Doppler cineloop recordings with that derived from conventional spectral Doppler in normal pregnancies. METHOD: In 18 uncomplicated pregnancies between 19 and 39 weeks' gestation, color Doppler was used to find the maximum velocity in the cross-sectional vessel area of a free-floating loop of the umbilical vein. The maximum velocity was determined using the software tool HDI_Lab (Philips Medical Systems) after tracing the vessel area of interest. Conventional spectral Doppler was then used to determine the maximum velocity with the High-Q machine option. The cross-sectional area of the umbilical vein was determined using B-mode imaging and was subsequently used to determine the umbilical volume flow from both Doppler methods. Assuming a parabolic flow profile in the umbilical vein, the mean velocity is equal to half the maximum velocity. The fetal weight was estimated from fetal biometry using the four-parameter Hadlock formula. RESULTS: Maximum velocity was significantly (P = 0.003) higher with color Doppler cineloop (14.3 +/- 2.5 cm/s) compared with spectral Doppler (12.7 +/- 3.2 cm/s). Therefore, using the same cross-sectional area for both methods, the umbilical blood flow was significantly higher (P = 0.001) with color Doppler cineloop (127.9 +/- 59.0 mL/min) than it was with spectral Doppler (112.8 +/- 54.1 mL/min). The umbilical blood flow expressed as volume flow per kg fetal weight was significantly (P = 0.01) higher with color Doppler cineloop (126.0 +/- 57.0 mL/min/kg) than it was with spectral Doppler (115.0 +/- 53.0 mL/min/kg). CONCLUSIONS: Umbilical venous flow velocity derived from color Doppler cineloops is approximately 10% higher than that derived from spectral Doppler-derived velocity. The reduced angle dependence of the color Doppler cineloop technique and the large sampling area of the cross-sectional vessel should allow better determination of the correct maximum velocity in the umbilical vein.

Wall shear stress and related hemodynamic parameters in the fetal descending aorta derived from color Doppler velocity profiles.

This paper presents a methodology for estimating the wall shear stress in the fetal descending aorta from color Doppler velocity profiles obtained during the second half of pregnancy. The Womersley model was applied to determine the wall shear stress and related hemodynamic parameters. Our analysis indicates that the aortic diameter can be modeled as a function of the gestational age in weeks as: Diameter (mm) = 0.17.ga + 0.15 (R2 = 0.64, p < 0.001). The aortic volume flow showed a log linear gestational age-related increase that fit the model: F (mL/min) = e(0.08.ga + 3.49) (R2 = 0.61, p < 0.001). The Womersley number increased linearly with gestational age from 3.3 to 6.2 (p < 0.001) and the pressure gradient decreased linearly from 2.68 to 1.16 mPa/mm (p = 0.003) during the second half of pregnancy; the mean wall shear stress for the study group was 2.2 Pa (SD = 0.59) and was independent of gestational age. This study suggests that the size of the fetal aorta adapts to flow demands and maintains constant mean wall shear stress.

On-line electrical impedance measurement for monitoring blood viscosity during on-pump heart surgery.

BACKGROUND: The viscosity of blood (eta) as well as its electrical impedance at 20 kHz at high shear rate depends on hematocrit, temperature, concentration of macromolecules and red cell deformability. The aim of our study was to investigate the relation between viscosity and electrical impedance in a heart-lung machine-like set-up, because during on-pump heart surgery considerable viscosity changes occur. METHODS: Blood of 10 healthy volunteers was examined under temperature variation between 18.5 and 37 degrees C at four different levels of hemodilution. Blood viscosity was examined with a golden-standard technique, i.e. a Contraves LS 30 Couette viscometer, and the results were compared with measurements of the electrical resistivity (R) at 20 kHz by a specially designed device in series with the tubing system of a heart-lung machine. All measurements were performed at a shear rate of 87 s(-1). RESULTS: Using stepwise multiparameter regression analysis (SPSS) a highly significant correlation was found (r(2) = 0.882) between viscosity (eta) and resistivity (R). Adding the variables sodium ([Na(+)]) and fibrinogen ([Fibr]) concentration the coefficient of correlation further improved to r(2) = 0.928 and the relation became: eta = -0.6844 + 0.038 R + 0.038 [Na(+)] + 0.514 [Fibr]. All coefficients showed a statistical significance of p < 0. 001. CONCLUSIONS: Electrical impedance measurement is feasible in a heart-lung machine-like set-up and allows accurate continuous on-line estimation of blood viscosity; it may offer an adequate way to record and control viscosity changes during on-pump heart surgery.

Fetal heart rate and umbilical artery flow velocity variability in intrauterine growth restriction: a matched controlled study.

OBJECTIVES: To study heart rate and umbilical artery blood flow velocity variability in growth-restricted fetuses and investigate the influence of the autonomic nervous system on these parameters. METHODS: Doppler velocity waveforms were collected from long-lasting umbilical artery recordings in 15 fetuses with growth restriction and 15 normal age-matched controls at 23-35 weeks of gestation. Absolute heart rate and umbilical artery blood flow velocity as well as the coefficient of variation were determined. Using power spectral analysis the low- and high-frequency bands of heart rate variability and blood flow velocity variability were calculated. The low-to-high (LH) ratio of heart rate variability and blood flow velocity variability were examined as a measure of sympathovagal balance. RESULTS: In growth-restricted fetuses umbilical artery velocities were significantly reduced. Heart rate variability was significantly reduced in the presence of growth restriction, but no significant difference was demonstrated for blood flow velocity variability. The LH ratio for heart rate variability was significantly decreased in growth restriction, but no difference in LH ratio was demonstrated for blood flow velocity variability. CONCLUSION: Flow velocity variability in growth restriction seems not to be predominantly influenced by the autonomic nervous system, whereas the decreased heart rate variability seems to be influenced by altered sympathetic-parasympathetic balance.

The impact of maternal plasma volume expansion and antihypertensive treatment with intravenous dihydralazine on fetal and maternal hemodynamics during pre-eclampsia: a clinical, echo-Doppler and viscometric study.

OBJECTIVES: To establish the effects of plasma volume expansion (PVE) followed by intravenous dihydralazine (DH) administration on maternal whole blood viscosity (WBV) and hematocrit, uteroplacental and fetoplacental downstream impedance and umbilical venous (UV) volume flow in pre-eclampsia. METHODS: In 13 pre-eclamptic women maternal and fetal hemodynamics were established by means of combined measurement of maternal arterial blood pressure (BP), WBV, hematocrit and uterine artery (UtA) resistance index (RI) in addition to umbilical artery (UA) pulsatility index (PI) and UV volume flow obtained from UV vessel area and UV time-averaged flow velocity. In each woman all parameters were measured four times at baseline, after PVE, after DH and 24 h after the start of treatment. RESULTS: Maternal diastolic BP, hematocrit and WBV display a significant reduction after PVE. In the fetus UA PI decreases significantly whereas a significant increase in UV cross-sectional area was detected. After maternal DH administration, arterial systolic and diastolic BP and UA PI show a significant decrease compared with the measurements following PVE. At 24 h, only maternal systolic and diastolic BP display a significant further decrease. No significant changes were established for the UtA RI, UV time-averaged velocity and UV volume flow during the entire study period. CONCLUSIONS: During pre-eclampsia, maternal PVE followed by DH administration results in a significant reduction in maternal diastolic BP, maternal hematocrit and WBV. Maternal PVE is associated with a significant increase in UV cross-sectional area and a non-significant rise of 11% in UV volume flow. Maternal DH administration does not result in any change in UV cross-sectional area. However, UA PI decreases significantly after both PVE and DH treatment.

Fetal heart rate and blood flow velocity variability in the presence of increased nuchal translucency: a preliminary study.

OBJECTIVE: To study the power spectrum distribution of heart rate and umbilical artery flow velocity variability in fetuses with increased nuchal translucency thickness (NT). METHODS: Doppler velocity waveforms were collected from long-lasting (>20 s) umbilical artery recordings in 18 fetuses with increased NT (>3 mm) and 18 normal controls matched for gestational age at 11-14 (median, 12) weeks. The NT group included 11 abnormal karyotypes: trisomy 18 (n = 3), 45,X (n = 4), trisomy 21 (n = 3) and a balanced translocation. Absolute heart rate as well as the coefficient of variation for both beat-to-beat heart rate variability and umbilical artery blood flow velocity variability were determined. The ratios of the integrated low-frequency components (0.05-0.2 Hz) and the integrated high-frequency ones (0.25-1.6 Hz; LH ratio) from normalized power spectrum distributions were established to reflect sympathovagal balance. RESULTS: The mean heart rate was not significantly different between the two groups. However, mean heart rate variability and time-averaged flow velocity variability were significantly increased in the NT group, while there was no significant difference in the LH ratios between the two groups. The mean umbilical artery pulsatility index was significantly higher in the NT group. CONCLUSION: The autonomic nervous system does not seem to play a role in the altered cardiovascular homeostasis in the presence of increased fetal NT.

Umbilical venous volume flow and fetal behavioral states in the normally developing fetus.

OBJECTIVE: To determine the relationship between umbilical venous (UV) volume flow and fetal behavioral states 1F (quiet sleep) and 2F (active sleep) in normal pregnancies at 36-40 weeks of gestation. METHODS: Fetal behavioral states were established in 17 normal pregnancies by means of combined assessment of fetal heart rate patterns (FHRP), and fetal eye and body movements. UV vessel area (mm(2)) as obtained by tracing the inner vessel area using Labview and Imaq Vision software and UV time-averaged flow velocity (mm/s Doppler) were multiplied to calculate UV volume flow (mL/min) including flow/kg fetus. The pulsatility index (PI) in the umbilical artery was also determined. In each woman, all parameters were measured between three and five times in each behavioral state. Data are reported as mean +/- 1 SD and analyzed by paired t-test. RESULTS: No statistically significant behavioral-state-related changes were observed for UV time-averaged velocity and UV volume flow, resulting in UV volume flow/kg fetus of 69.1 +/- 14.9 mL/min*kg at 1F and 71.6 +/- 12.1 mL/min*kg at 2F (not significant). A statistically significant increase (P = 0.02) was established for UV cross-sectional area (46.4 +/- 8.6 mm(2) vs. 49.0 +/- 10.1 mm(2)) and for fetal heart rate (FHR) from 134.2 +/- 10.3 bpm in 1F to 144.2 +/- 7 bpm in 2F. Umbilical artery PI was not significantly different between the two behavioral states. CONCLUSIONS: On the basis of high venous vessel wall compliance, the significant increase in UV cross-sectional area during fetal behavioral state 2F may be determined by a rise in mean venous pressure. The significant rise in FHR may reflect increased fetal cardiac output during state 2F while the resistance at the hepato-ductal pathway remains relatively constant with the purpose of meeting raised energy demands during the active sleep state. This is further supported by the observed trend towards an increase in UV volume flow.

Fetal brain/liver volume ratio and umbilical volume flow parameters relative to normal and abnormal human development.

OBJECTIVES: To estimate fetal brain volume from head circumference and published postmortem data; to determine normal values for the fetal brain/liver volume ratio relative to gestational age; to establish the relationship between the brain/liver volume ratio and fetal circulatory parameters during normal and restricted (SGA) fetal growth. PATIENTS AND METHOD: This was a cross-sectional study involving a total of 47 uncomplicated pregnancies appropriate-for-gestational age (AGA) and 23 pregnancies resulting in the delivery of a SGA fetus. At enrollment gestational age ranged between 20 and 36 weeks in both groups. Umbilical venous cross-sectional area and time-averaged velocity for calculation of volume flow as well as velocity waveforms from the umbilical artery, middle cerebral artery and ductus venosus, were recorded. Fetal liver volume measurements were obtained using three-dimensional ultrasound. Fetal brain volume was estimated from fetal head volume following comparison with published postmortem data on fetal brain weight. RESULTS: A significant correlation was observed between prenatally estimated fetal head volume and postmortem fetal brain volume. Fetal brain volume was approximately half that of fetal head volume. The normal fetal brain/liver volume ratio demonstrated a significant reduction with gestational age (R = -0.54; P < 0.001). The normal mean +/- standard deviation (SD) fetal brain/liver volume ratio (3.4 +/- 0.7) was significantly different (P < 0.001) from the mean fetal brain/liver volume ratio in the SGA group (n = 23) (5.9 +/- 1.9). A significant difference existed for mean umbilical venous volume flow between AGA (104.7 +/- 26.9 mL/min/kg) and SGA (59.6 +/- 22.7 mL/min/kg) fetuses. In the SGA fetus, there was a significant inverse relationship (P < 0.001) between fetal weight-related umbilical venous volume flow and fetal brain/liver volume ratio. In a subset of 16 SGA and 16 AGA fetuses matched for gestational age, a significant difference existed for umbilical artery pulsatility index (2.30 +/- 1.52 vs. 0.99 +/- 0.19), fetal middle cerebral artery pulsatility index (1.3 +/- 0.4 vs. 2.1 +/- 0.3) and late diastolic flow velocity in the fetal ductus venosus (6.9 +/- 14.2 cm/s vs. 23.9 +/- 8.8 cm/s), but not for peak systolic, early diastolic and time-averaged velocity in the ductus venosus. CONCLUSION: Sonographic estimates of fetal brain volume can be obtained. The fetal brain/liver volume ratio is a predictor of fetal outcome in the growth-restricted fetus. An inverse relationship exists in SGA fetuses between brain/liver volume ratio and fetal weight-related umbilical venous blood flow.

Cervical dilatation related to uterine electromyographic activity and endocrinological changes during prostaglandin F(2alpha)-induced parturition in cows.

The temporal relationship between changes in cervical dilatation, uterine electromyographic (EMG) activity, and maternal plasma concentrations of estradiol 17beta (E(2)), progesterone (P(4)), and 13,14-dihydro-15-keto-prostaglandin-F(2alpha) (PGFM), was investigated in six parturient cows. Calving was induced with a single injection of a synthetic analogue of prostaglandin F(2alpha) (PG) on Day 274 of gestation. Cervical dilatation was measured continuously by measuring the transit time between two implanted ultrasound crystals while at the same time uterine EMG activity was measured through two silver electrodes sutured on the myometrial surface until the expulsive stage of calving had been reached. In blood samples collected at 4-h intervals, starting at the moment of PG injection, the mean plasma E(2) concentration gradually increased and was significantly elevated at 28 h after PG injection. At 4 h after PG treatment, the mean P(4) concentration had dropped significantly and continued to decrease until a value of around 1 ng/ml was reached, where it stayed until the onset of expulsion. Mean plasma PGFM concentrations increased steadily after PG injection, reaching significantly elevated concentrations at 20 h after treatment. In the five cows that delivered calves in anterior positions, uterine EMG activity, expressed as root mean square (RMS in microV), started to increase at a mean interval (+/- SD) of 13.1 +/- 3.7 h following PG treatment. The increase in EMG activity was significantly correlated with changes in plasma PGFM concentrations. In these cows, dilatation of the caudal cervix started after a mean (+/- SD) interval of 28.5 +/- 1.5 h following PG treatment and dilatation progressed at a mean (+/- SD) rate of 2.25 +/- 0.24 cm/h. In one cow with a calf in the posterior position, uterine EMG activity and dilatation started at 15.8 h and 31.8 h, respectively, after induction of calving. We conclude that a predictable sequence of physiological changes occurs around induction of calving, which allows specific timing of future studies on cellular and biochemical changes within the cervix during parturition.

Ultrasonic cervimetry to study the dilatation of the caudal cervix of the cow at parturition.

The objective of this study was to investigate the temporal changes in dilatation of the caudal cervix during induced calvings (n = 5). We used ultrasound cervimetry, allowing the continuous recording of the distance between a transmitting and receiving ultrasound crystal, which were implanted opposite to each other on the caudal rim of the cervix. We started recording between 19 and 21 h after injecting a prostaglandin analogue (PG) on day 272 of gestation. A fluid-filled catheter had been introduced transcervically between the fetal membranes and the uterine wall for measurements of intra-uterine pressure (IUP). While the characteristics of calving varied widely between the five animals, it appeared possible to divide the process of dilatation into four phases. During the latent phase, which lasted until 25-43 h after PG, no net gain in dilatation occurred. We found an acceleration phase (4.3-6.8 h), in which the dilatation rate speeds up (0.49-0.84 cm/h) in three of the cows. During the phase of maximum slope (lasting 0.5-4.8 h), we measured an even higher rate (1.47-8.48 cm/h), decreasing again during the deceleration phase (rate 0.24-2.28 cm/h) in four cows. The quality of the IUP measurements precluded us from continuously investigating the relationship between cervical dilatation and uterine contractions. However, short term simultaneous recordings revealed that the cervical opening changed momentarily in the absence of IUP during the latent phase, while during the phase of maximum slope, temporary changes of dilatation coincided with uterine contractions. We concluded that the method of ultrasound cervimetry used in this study provides a valuable way to study the process of cervical dilatation in parturient cows in vivo.

Umbilical venous volume flow in the normally developing and growth-restricted human fetus.

OBJECTIVE: To determine the reproducibility of measurement of umbilical venous volume flow components and to calculate umbilical venous volume flow in normal and growth-restricted (small-for-gestational age) fetuses in a cross-sectional study. METHOD: Using Labview and Imaq-vision software, the cross-sectional inner area of the umbilical vein was traced. Vessel area (mm2) and Doppler-derived time-averaged flow velocity (mm/s) were multiplied to calculate volume flow (mL/min) including flow per kg fetal weight. The coefficient of variation for vessel area and flow velocity scans and tracings were determined (n = 13; 26-35 weeks). Normal charts for components and volume flow were constructed (n = 100; 20-36 weeks) and related to data from growth restricted fetuses (birth weight < 5th centile) (n = 33; 22-36 weeks). In growth-restricted fetuses the umbilical artery pulsatility index was also obtained. RESULTS: Reproducibility: The coefficient of variation was 5.4% (vessel area) and 7.3% (time-averaged velocity) for scans and 6.6% and 10.5% for measurements, resulting in a coefficient of variation of 8.1% (scans) and 11.9% (measurements) for volume flow. A gestational age-related increase exists for vessel area, time-averaged flow velocity and umbilical venous volume flow from 33.2 (SD, 15.2) mL/min at 20 weeks to 221.0 (SD, 32.8) mL/min at 36 weeks of gestation, but there is a reduction from 117.5 (SD, 33.6) mL/min to 78.3 (SD, 12.4) mL/min for volume flow per kg fetal weight. In small-for-gestational age fetuses, the values were below the normal range in 31 of 33 cases for volume flow and in 21 of 33 cases for volume flow per kg fetal weight. Umbilical artery pulsatility index was significantly different between the subsets with normal and those with reduced volume flow per kg fetal weight. CONCLUSIONS: Measurements of umbilical venous vessel area and time-averaged velocity resulted in acceptable reproducibility of volume flow calculations, which show a seven-fold increase at 20-36 weeks of gestation. In growth-restricted fetuses, volume flow is significantly reduced. When calculated per kg/fetus, the values were reduced in 21 (63.6%) out of 33 cases.

Anal sphincter damage after vaginal delivery: functional outcome and risk factors for fecal incontinence.

OBJECTIVE: To assess the role of anal sphincter damage following delivery in the development of anorectal complaints and urinary incontinence, and to identify obstetric factors associated with subsequent fecal incontinence. METHODS: The retrospective cohort study with matched controls used a postal questionnaire and analysis of delivery and operation records from all women who underwent primary repair of a third or fourth degree perineal rupture in our hospital between 1971 and 1991, and their controls, matched for date and parity. Frequencies of complaints were compared using the Mantel-Haenszel common odds ratio [OR] for matched-control studies. Obstetric risk factors for fecal incontinence were assessed with multivariate logistic regression analysis. RESULTS: In the period studied, 171 women underwent a primary repair. One hundred and forty-seven of which returned the questionnaire (86%), compared with 131 of the controls (73%). Analysis was performed on 125 matched pairs with a median follow-up of 14 years. Fecal incontinence was reported by 39 patients and 16 controls (OR: 3.09; 95% confidence interval: 1.57-6.10). Urinary incontinence was reported by 65 cases and 52 controls (OR:1.46; 95% CI: 0.91-2.37). Among women with anal sphincter damage, the extent of anal sphincter damage was an independent risk factor for fecal incontinence. (OR: 2.54; 95% CI: 1.45-4.45). Subsequent vaginal delivery was not associated with the development of fecal incontinence (OR: 2.32; 95% CI: 0.85-6.33). In primiparous women mediolateral episiotomy protected for fecal incontinence after anal sphincter damage (OR: 0.17; 95% CI: 0.05-0.60). CONCLUSIONS: Anal sphincter damage following delivery is significantly associated with subsequent anorectal complaints, but not with urinary incontinence. The extent of sphincter damage is an independent risk factor for the development of fecal incontinence. Mediolateral episiotomy protects for fecal incontinence in primiparous women.

Dorsal aortic flow velocity in chick embryos of stage 16 to 28.

The objective of this study was to evaluate two Doppler frequency-detection methods to measure blood flow velocity in the developing chick embryo. We compared the commonly used directional zero-crossing counter and a customized digital bidirectional spectrum analyzer. At development stages 16 up to 28 (2.5 to 6 days incubation), a reversed flow component in the dorsal aorta was demonstrated using the bidirectional spectrum analyzer. Dorsal aortic velocities obtained with the directional zero-crossing counter were significantly lower than with the bidirectional spectrum analyzer in stages 16, 20 and 28. In addition to the differences in the absolute velocity values, there was also a remarkable discrepancy in the velocity waveform shape using the two Doppler frequency processors. The calculated heart rate using the two Doppler frequency processors was identical. It is concluded that a Doppler velocity detector based on spectral analysis is superior to the hitherto used zero-crossing counter in the chick embryo. With the customized digital bidirectional spectrum analyzer, we can accurately measure the hemodynamics of the developing chick embryo.

Power spectrum analysis of heart rate and blood flow velocity variability measured in the umbilical and uterine arteries in early pregnancy: a comparative study.

OBJECTIVE: To compare power spectral derived variability parameters from the fetal side of the placental circulation with those from the maternal side of the placental circulation, during early pregnancy. METHODS: Doppler velocity waveforms were obtained from both the umbilical and the uterine arteries in a study group of 40 pregnant women between 10 and 14 (n = 25) and 15 and 20 (n = 15) weeks of gestation. The coefficient of variation of both the beat-to-beat heart rate variability and the blood flow velocity variability was determined. The ratio of the integrated low-frequency components (< 0.2 Hz) and the integrated high-frequency components (> 0.2 Hz) from normalized power spectrum analysis (LH-ratio) was established, to reflect sympathovagal balance. RESULTS: The coefficient of variation and LH-ratio of fetal heart rate variability constitute only a fraction of the same maternal heart rate variability parameters. Nevertheless a highly significant increase (P < 0.001) in LH-ratio was demonstrated with advancing gestational age. The coefficient of variation and LH-ratio of blood flow velocity variability were significantly lower in the fetal umbilical artery only in the 10-14-weeks' gestation group. Due to a decrease of the maternal uterine blood flow velocity variability parameters with advancing gestational age, statistically equal fetal and maternal values for coefficient of variation and LH-ratio were found in the 15-20 weeks' gestation group. CONCLUSIONS: The increase in LH-ratio of fetal heart rate variability indicates functional development of the fetal autonomic nervous system at 15-20 weeks' gestation. The umbilical blood flow velocity variability may be secondary to maternal uterine arterial flow variability rather than due to primary changes in fetal cardiovascular function.

Risk factors for third degree perineal ruptures during delivery.

OBJECTIVE: To determine risk factors for the occurrence of third degree perineal tears during vaginal delivery. DESIGN: A population-based observational study. POPULATION: All 284,783 vaginal deliveries in 1994 and 1995 recorded in the Dutch National Obstetric Database were included in the study. METHODS: Third degree perineal rupture was defined as any rupture involving the anal sphincter muscles. Logistic regression analysis was used to assess risk factors. MAIN OUTCOME MEASURES: An overall rate of third degree perineal ruptures of 1.94% was found. High fetal birthweight, long duration of the second stage of delivery and primiparity were associated with an elevated risk of anal sphincter damage. Mediolateral episiotomy appeared to protect strongly against damage to the anal sphincter complex during delivery (OR: 0.21, 95% CI: 0.20-0.23). All types of assisted vaginal delivery were associated with third degree perineal ruptures, with forceps delivery (OR: 3.33, 95%-CI: 2.97-3.74) carrying the largest risk of all assisted vaginal deliveries. Use of forceps combined with other types of assisted vaginal delivery appeared to increase the risk even further. CONCLUSIONS: Mediolateral episiotomy protects strongly against the occurrence of third degree perineal ruptures and may thus serve as a primary method of prevention of faecal incontinence. Forceps delivery is a stronger risk factor for third degree perineal tears than vacuum extraction. If the obstetric situation permits use of either instrument, the vacuum extractor should be the instrument of choice with respect to the prevention of faecal incontinence.

Serum thrombopoietin levels in relation to disease status in patients with immune thrombocytopenic purpura.

Pre- and post-treatment serum thrombopoietin (TPO) concentration was measured in 35 patients with immune thrombocytopenic purpura (ITP). Mean post-treatment levels were significantly lower (P = 0.02) than pretreatment and not different for treatment modality. No significant correlation between pre- or post-treatment TPO and platelet counts was demonstrable (R = -0.325, P = 0.056 and R = -0.227, P = 0.190 respectively). In patients with very low platelet counts (< or =20 x 10(9)/l), pretreatment serum TPO was significantly higher than in patients with higher counts (P = 0.033). The logarithm of the platelet turnover rate, measured in 15 patients, correlated with pretreatment TPO levels (R = 0.64). These findings suggest a contributory role for TPO in the mechanism of ITP.