妊高征患者胎儿脐动脉及大脑中动脉血流动力学研究

目的探讨妊娠高血压综合征(PHI)患者胎儿脐动脉(UA)及大脑中动脉(MCA)的血流动力学变化规律,评价彩色多普勒血流显像技术在PIH上的利用价值。方法 应用彩色多普勒血流显像术检测95例正常晚期妊娠和52例PHI患者胎儿UA的搏动指数(PI)、阻力指数(RI)及MCA的搏动指数(PI)、阻力指数(RI),计算MCA—PI/UA—PI、MCA—RI/UA—RI的比值,均取平均值比较。结果PIH组与正常组UA—PI值比较有明显增高(P<0.01),而UA—RI值二组比较差异无显著性(P>0.05);MCA—PI值与MCA—RI值仅在重度PIH组与正常组间比较有显著降低(P<0.01);MCA—PI/UA—PI及MCA—RI/UA—RI的比值与正常组比较均有明显降低(P<0.01);重度PIH组MCA—PI/UA—PI及MCA—RI/UA—RI的比值二者均小于1。预测围产儿结局方面,MCA—PI/UA—PI具有高的敏感性(88.89％)、特异性(97.06％)、阳性预测值(94.12％)及阴性预测值(94.28％),其诊断指数最高为0.86,且与单一血管比较差异有显著性(P<0.01)。结论妊高征患者胎儿的胎盘循环与颅脑循环的血流动力学变化规律不一致,二者结合在预测妊高征病情发展程度和预测围产儿结局方面有重要的临床价值。     

妊高征患者血液流变学与脐血流动力学的相关性研究

目的探讨妊高征患者血液流变学与胎儿脐动脉血流阻力指标的相关性和对围产儿结局的影响。方法用粘度仪检测妊高征孕妇全血比粘度高切（ＢＶＨ）、全血比粘度低切（ＢＶＬ）、全血还原比粘度、血浆粘度（ＰＶ）;用离心机检测红细胞压积（ＨＣＴ）;应用彩色多普勒检测胎儿脐动脉血流阻力指标,比较妊高征患者血液流变学各值与胎儿脐动脉血流阻力指标各值相关关系。结果妊高征患者血液流变学各值与胎儿脐动脉血流阻力指标各值呈正相关性;ＨＣＴ、ＢＶＨ、ＢＶＬ、ＰＶ对妊高征的发生、发展及严重程度及脐动脉血流阻力指标有重要影响,导致胎儿胎盘循环障碍,脐动脉血流阻力指标升高。围产儿结局不良发生率,中、重度妊高征高于轻度妊高征（Ｐ＜０．０１）。结论多项指标监测妊高征血液流变学及胎儿脐血流动力学,可提高预测妊高征发生、发展及严重程度和对围产儿预后影响的准确性。     

Doppler flow characteristic in inferior vena cava between 22-42 weeks in intrau-terine growth restriction and normal pregnancies

Uterine blood flow restriction and placental insufficiency can cause intrauterine grow restriction. Permanent hypoxia triggers compensatory mechanisms to pro-tect vital organs. Increased placental resistance and constriction of the fetal pe-ripheral vessels, as evidenced by blood redistribution and increased right ven-tricular afterload and end-diastolic pressure lead to increased pulsality in pre-cordial veins. Doppler flow analysis of the IVC allows the indirect estimation of the fetal heart function. OBJECTIVE: The aim of the study was to compare the Doppler indices in IVC in growth restricted and normal fetuses. RESULTS: The authors found that for the normal group PVIV, PIV and S/D de-creased with advancing gestation. However in comparision in IUGR group these parameters were substantially higher. CONCLUSIONS: The improvement of maternal and fetal Doppler techniques allows us to distinguish the subgroups of IUGR fetuses with the uteroplacental insufficiency that will have an increased perinatal morbidity and mortality. Alterations in the venous blood velocity waveforms have a more precise relationship with the risk of adverse perinatal outcome than changes in the arterial blood flow usually recognized relatively early in placental function disorders.     

Fetal and uteroplacental haemodynamics during short-term atenolol treatment of hypertension in pregnancy

Fetal circulation was studied by means of combined real-time and pulsed Doppler ultrasound in 14 women with pregnancy-associated hypertension before and during the first and third days of treatment with the beta 1-selective blocker, atenolol; in seven of the women the maternal uterine arcuate blood velocity waveform was also studied. Blood flow characteristics were normal both in the fetus and in the maternal arcuate artery, compared with those in uncomplicated pregnancies of corresponding gestational ages. Volume blood flow remained unchanged in the fetal descending aorta, and in the umbilical vein during atenolol treatment, whereas the pulsatility index increased in the fetal descending aorta and in the arcuate artery. This suggests that the peripheral vascular resistance, both on the maternal and fetal side of the placenta, increased during short-term antihypertensive treatment with atenolol.     

The acute response of the umbilical artery pulsatility index to changes in blood volume in fetal sheep.

This experimental study was designed to test the effects of acute changes in fetal circulating blood volume on the umbilical artery pulsatility index (PI). Six fetal sheep were provided with an electromagnetic flow meter for measurement of umbilical venous blood flow, with catheters for determination of arterial blood pressure and umbilical venous pressure, and with a 5 MHz Doppler transducer around one umbilical artery for flow velocity waveform analysis. A catheter in the inferior vena cava was used to infuse 50 ml of maternal blood (hypervolemia) into the fetal circulation or to withdraw 50 ml of fetal blood (hypovolemia) after volume correction. Hypervolemia resulted in a rise in arterial pressure and umbilical venous pressure, without an effect on PI, umbilical blood flow or placental vascular resistance. Hypovolemia resulted in a decrease in fetal heart rate, arterial pressure, umbilical venous pressure and umbilical blood flow. Calculated placental vascular resistance was not changed, whereas the PI increased by 42%. We conclude that volume loading with 10-15% of fetal circulating volume does not affect the umbilical artery PI, whereas acute reduction of fetal blood volume with the same amount is associated with an increase in the umbilical artery PI, without changes in calculated placental vascular resistance.     

Clinical and experimental studies on the pathogenesis in pregnancy induced hypertension

Placental ischemia is one of the etiological factors of pregnancy induced hypertension (PIH), however, the pathogenesis of placental and renal ischemia has not been clarified. The purposes of this investigation are (1) to clarify the fetomaternal hemodynamic changes in PIH and the influence of maternal postural change on fetomaternal hemodynamics, measured by thermodilution method, impedance cardiography and pulsed doppler method during pregnancy, (2) to provide to relationship between intrauterine resting tonus and maternal hemodynamics, that is, blood pressure, placental and renal blood flow measured by electromagnetic flowmeter and thermocouple method, and renal nerve activity, and (3) to study the influence of placental ischemia on vascular sensitivity to angiotensin II measured by Magnus method in animal experiment. (1) The increase in C.O and blood volume were recognized from the beginning of pregnancy to 24 GW, and subsequently, the decreasing tendency were found from about 32 GW to the onset of labor. However this decreasing tendency were subsided in the lateral position. These circulatory changes were observed in both normotensive and PIH cases, and especially, the decrease in C.O and blood volume in late pregnancy were more remarkable in PIH than that in normotensive pregnancy. From the results of Starling curve, left ventricular work was more hyperdynamic status in PIH than that in normotensive pregnancy, these results show that there are a compensatory mechanism against high vascular resistance in PIH. A/B (S/D) ratio in uterine artery, umbilical artery and fetal aorta were lowered in II-nd and III-rd trimester and more decreased in the lateral position from the supine position, on the other hand these ratio in PIH were elevated respectively. These results show that there are the aortocaval compression by the heavy tensive uterus and subsequent sluice flow mechanism in fetoplacental circulation in the supine position in late pregnancy. (2) These vascular compression were recognized very often in PIH accompanying with increasing in uterine resting tonus. It was recognized in pregnant rabbit that an increase in uterine resting tonus in the ovarian side caused an increasing blood pressure, a decrease in renal and placental blood flow and an increase in renal sympathetic nerve activity (RSNA). After resection of the suspensory ligament of ovarii, an increase in resting tonus in the ovarian side did not only cause an increase in RSNA, but also a decrease in renal blood flow.(ABSTRACT TRUNCATED AT 400 WORDS)     

Doppler examinations of fetal and uteroplacental blood flow in AGA and IUGR fetuses before and after maternal physical exercise with the bicycle ergometer

OBJECTIVE: To study changes in uteroplacental and fetal circulation after maternal exercise in appropriate-for-gestational-age fetuses (AGA) and intrauterine-growth-retarded fetuses (IUGR). MATERIALS AND METHOD: 33 women with an uncomplicated course of pregnancy and ten women with IUGR were examined. Physical stress was caused through a bicycle ergometer with 1.25 W/kg maternal weight. Doppler examinations were performed in the umbilical artery, fetal aorta, middle cerebral and in the uterine artery. Fetal heart rate was documented by monitoring. Maternal lactate and glucose levels as well as maternal blood pressure and heart rate were recorded. RESULTS: No significant changes after cycling could be observed in umbilical and uterine vessels either in the normal pregnancies or in pregnancies with IUGR. In contrast, in the fetal aorta an increase of the RI was recorded in both groups (an increase of 16% [P<0.01] and 18% [P<0.05], respectively for AGA and IUGR cases). In cerebral arteries a decrease of the RI was observed after cycling in both groups (a decrease of 24% [P<0.01] and 13% [P<0.05], respectively for AGA and IUGR cases). In AGA fetuses the RI of the aorta and middle cerebral artery returned to pre-test level by the 18th minute of examination. In IUGR fetuses the RI of the aorta and middle cerebral artery did not return to pre-test levels at the end of the test. Fetal heart rate remained unchanged in both groups. Maternal blood pressure and heart rate increased during the exertion phase but returned to initial values at the end of the test. A 21% and 24% (for AGA and IUGR groups respectively) reduction of maternal glucose values after exercise was observed (P<0.001). Lactate values doubled in both groups after exercise (P<0.001). CONCLUSION: From the results obtained we conclude that maternal exercise does not significantly alter uterine and umbilical perfusion in AGA and IUGR pregnancies, suggesting an absence of change in the uterine vascular bed resistance. However, submaximal maternal exercise was followed by fetal cerebral vasodilatation and an increase of resistance in the fetal aorta that was more evident in IUGR fetuses. This might be due to slight fetal hemoglobin desaturation in those cases.     

Doppler flow characteristics in ductus venosus between 22-42 weeks in intrauterine growth restriction and normal pregnancies

OBJECTIVES: The ductus venosus plays an important role in the oxygenated blood supply from the placenta directly to the fetal heart. Uterine blood flow restriction and placental insufficiency can cause intrauterine grow restriction. Permanent hypoxia triggers compensatory mechanisms to protect vital organs. Increased placental resistance and constriction of the fetal peripheral vessels, as evidenced by blood redistribution and increased right ventricular afterload and end-diastolic pressure lead to increased pulsatility in precordial veins. Doppler flow analysis of the DV allows the indirect estimation of the fetal heart function. Because it is not always possible to achieve correct ultrasound beam insonation there have been attempts to use angle-independent indices. The aim of the study was: to compare the Doppler indices in DV in growth restricted and normal fetuses. MATERIAL AND METHODS: 208 women were analyzed: 89 women between 22-42 weeks of pregnancy complicated by IUGR and 119 with normal pregnancy as a control group. Ultrasound examination using pulse and color Doppler was performed and PVIV, PIV, PLI and S/D ratio were estimated. RESULTS: The authors found that for the normal group PVIV, PIV, PLI and S/A decreased with advancing gestation. However in comparison in IUGR group these parameters were substantially higher. CONCLUSIONS: The improvement of maternal and fetal Doppler techniques allows us to distinguish the subgroups of IUGR fetuses with the uteroplacental insufficiency that will have an increased perinatal morbidity and mortality. Alterations in the venous blood velocity waveforms have a more precise relationship with the risk of adverse perinatal outcome than changes in the arterial blood flow usually recognized relatively early in placental function disorders.     

Ultrasound of the placenta: a systematic approach. Part II: functional assessment (Doppler)

Doppler velocimetry is the ideal clinical tool to assess placental performance in high-risk pregnancies. It also has value in predicting later complications and outcome in pregnancies which appear uncomplicated. All three circulations (fetal, placental and maternal) may be interrogated by Doppler technology. In the following review, we present basic physics aspects of Doppler and discuss mainly Doppler investigation of the fetal-placental circulation (umbilical artery, intraplacental circulation) as well as the uterine arteries. The assessment of umbilical blood flow provides information on blood perfusion of the fetal-placental unit. The diastolic blood flow velocity component in umbilical artery increases with advancing gestation. In pregnancies complicated by placental dysfunction, there may be a reduction in the number of functional villi and/or small blood vessels with, as a result, increased impedance, reflected, mainly, by a decrease in end-diastolic velocity. When the resistance increases even more, there is no diastolic forward velocity (absent end-diastolic velocity). Further increase in the resistance causes reversed end-diastolic velocity, which is considered a late step in the cascade of events leading to intrauterine fetal demise. Doppler assessment of the umbilical arteries was found to improve outcome of high-risk pregnancies, and reduce hospital admissions. On the contrary, routine Doppler ultrasound in low risk or unselected populations does not seem to confer benefit on mother or newborn. Uterine artery Doppler is a useful test in predicting pregnancies at high risk of developing complications related to uteroplacental insufficiency. It identifies women who may benefit from increased antenatal surveillance or prophylactic therapy. Three-dimensional power Doppler sonography can provide new insights into placental pathophysiology.     

Structural changes in umbilical vessels in pregnancy induced hypertension

BACKGROUND: Pregnancy Induced Hypertension (PIH) is associated with placental morphological changes, alterations in the blood flow patterns in the umbilical vessels and adverse fetal and maternal outcome. Studies have demonstrated changes in the structure of the umbilical vessels but these have not been described across the length of the cord or correlated with the severity of disease. STUDY DESIGN: A case control study. SETTING: Kenyatta National Hospital. MATERIALS AND METHODS: Thirty six umbilical cords from newborns of women with and without PIH (18 cases, 18 controls) were obtained and studied with light microscopy. Of the cases 9 women had severe PIH and 9 had mild PIH. Means and standard deviations for the various parameters of the various groups were obtained. Student's t-test and ANOVA were used to compare means, a p value of <0.05 being significant. RESULTS: The structure of the umbilical vessels changes from the placental end to the fetal end. The umbilical vein in PIH had a greater wall thickness and a smaller luminal area than in the controls. The vein's wall-luminal ratio increased from the placental to the fetal end. Duplication of the elastic subintimal lamina (ESL) was higher in the cases. The ESL was more commonly duplicated in the fetal end. There were no structural differences between the umbilical arteries in PIH and in the controls. CONCLUSION: PIH is associated with structural changes in the umbilical vessels. These changes are more predominant in the vein than in the artery and in the vein, they are more obvious in the fetal end. The observed increase in wall-luminal ratio from the placental to the fetal end suggests that the fetal end of the umbilical vein has a more refined role in the regulation of blood flow to the fetus.     

Assessment of nitrite oxide and maternal–fetal Doppler parameters during pregnancy

Objective: The objective was to evaluate and compare the whole blood nitrite concentration in the three trimesters of pregnancy. Additionally, we investigate whether there is any relation between nitrite concentrations and Doppler ultrasound analysis of some maternal and fetal vessels.

Methods: Thirty-three healthy pregnant women were examined at the first (11–14 weeks), second (20–24 weeks) and third trimester (34–36 weeks) of pregnancy. In the three exams, we determined the maternal whole blood nitrite concentration and uterine arteries Doppler analysis to determine pulsatility index (PI), and resistance index (RI). In the second and third trimester we also performed fetal umbilical and middle cerebral arteries PI and RI. We compared the concentrations of nitrite in three trimesters and correlated with Doppler parameters.

Results: No difference was observed in the whole blood nitrite concentrations across trimesters: 151.70?±?77.90?nmol/ml, 142.10?±?73.50?nmol/ml and 147.10?±?87.30?nmol/ml; first, second and third trimesters, respectively. We found no difference in correlation between whole blood nitrite concentration and Doppler parameters from the evaluated vessels.

Conclusions: In healthy pregnant women, the nitrite concentrations did not change across gestational trimesters and there was also no strong correlation with Doppler impedance indices from maternal uterine arteries and fetal umbilical and middle cerebral arteries.     

孕妇体位变换对母儿循环的影响

随意抽样正常妊娠２７～４０周孕妇５０例。仰卧位１５分钟后改为左侧卧位。用脉冲多普勒诊断装置分别测定其右侧子宫动脉（ＵｔＡ）、脐动脉（ＵＡ）、胎儿腹主动脉（ＤＡ）的血流速波形，并从连续且稳定的五个血流速波形计算血管阻力指数（ＲＩ），按２７～３２周，３３～３４周，３５～３６周、３７～３８周，３９～４０周分为五组，进行统计学分析。结果如下：（１）妊娠周数与ＵＡ－ＲＩ间呈负相关关系（ｒ＝４０４４，Ｐ＜０．０５）；（２）妊娠３７周后，孕妇体位变换引起ＵｔＡ－ＲＩ、ＵＡ－ＲＩ明显降低；（３）左侧卧位时，ＵｔＡ－ＲＩ与ＵＡ－ＲＩ间明显相关（ｒ＝０．４００８，Ｐ＜０．０５）；（４）左侧卧位的ＤＡ－ＲＩ值较仰卧位时低，但差异无显著性。提示：妊娠后期，孕妇体位变换对母儿循环有影响，取左侧卧位有利于胎儿发育。     

正常妊娠及妊高征患者静脉血及新生儿脐血一氧化氮含量的测…

探讨一氧化氮含量与妊娠及妊高征的关系。方法,采用硝酸根还原酶与Ｇｒｉｅｓｓ反应相结合的方法,对４０例妊高征患者、４０例正常晚期妊娠妇女、２０例非孕妇女静脉血及妊高征组和晚孕组各２８例新生儿脐血中的ＮＯ代谢产物亚硝酸基／硝酸基进行测定。     

Labetalol does not alter the placental and fetal blood flow or maternal prostanoids in pre-eclampsia

The effect of intravenously administered labetalol (1 mg/kg) on placental and fetal blood flow was studied in 13 pre-eclamptic women. Although the maternal blood pressure decreased, no changes occurred in the blood flows in the intervillous space, the umbilical vein or the fetal descending aorta, nor did the indices of peripheral vascular resistance in the fetal aorta change, but the placental vascular resistance did decrease. Labetalol had no effect on prostacyclin or thromboxane A2 as measured by urinary 6-keto-prostaglandin F1 alpha and serum thromboxane B2 respectively. These findings are clinically relevant since they suggest that labetalol reduces maternal blood pressure without interfering with the placental or fetal blood flow.     

Lack of relation between fetal blood gases and fetal blood flow velocity waveform indices found in rhesus isoimmunised pregnancies.

OBJECTIVE: To investigate the relation between umbilical vein blood gas components and the vascular resistance in four fetal arteries in Rh-immunised pregnancies. DESIGN: A prospective observational study over a 4-month period. SETTING: King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia. SUBJECTS: Fifteen Rh-isoimmunised pregnant women. INTERVENTIONS: Pulsed Doppler examinations of the umbilical artery, fetal internal carotid artery, thoracic aorta and abdominal aorta before transabdominal fetal blood sampling from the umbilical vein on 38 occasions. MAIN OUTCOME MEASURES: Doppler flow velocity pulsatility index (PI), systolic/diastolic ratio (A/B) and resistance index (RI) in the four fetal arteries investigated were related to the umbilical vein blood gases and acid-base status (PO2, PCO2, O2-content, CO2-content, HCO3, base excess and lactate concentration). RESULTS: There were no correlations between the Doppler indices in any of the vessels studied and the blood gases components in the umbilical vein. The ratios between the corresponding Doppler indices in the different vessels were also independent of the blood gases and acid-base status and there were no significant differences in the Doppler indices in the same vessel between fetuses with blood gas values over the 75th centile and those with values below the 25th centile. CONCLUSION: This study does not support a reduction in peripheral vascular resistance in the fetal cerebrum in relation to fetal hypoxia in Rh-immunized pregnancies.     

The effect of loading dose of magnesium sulfate on uterine,umbilical, and fetal middle cerebral arteries Doppler in women with severe preeclampsia: A case control study

IV MgSO₄ administration in women with severe preeclampsia resulted in a decrease in umbilical artery, uterine artery, and fetal middle cerebral artery Doppler indices.

Objective: To evaluate Doppler parameters of the umbilical artery (UmA), uterine artery (UA), and fetal middle cerebral artery (MCA) before and after MgSO₄ administration in women with severe preeclampsia. Methods: A case control study included 100 pregnant women with severe preeclampsia. Umbilical artery, uterine artery, and fetal middle cerebral artery Doppler were measured before and 20 minutes after intravenous administration of 6 g of magnesium sulfate. Results: There was a significant difference between maternal systolic blood pressure (173.20 ± 22.72 vs. 156.60 ± 19.18), diastolic blood pressure (109.60 ± 9.14 vs. 101.90 ± 10.05), and heart rate (80.52 ± 11.52 vs. 88.48 ± 12.08) before and after administration of MgSO₄ in the studied patients (p value < 0.001). There was a significant difference between umbilical artery, middle cerebral artery, and uterine artery Doppler parameters before and after administration of MgSO₄ in the studied patients (p value < 0.001). There was no significant difference between umbilical artery/middle cerebral artery with regard to RI and PI. However, there was significant difference with regard to the S/D ratio (p value < 0.001). The decrease in the values of Doppler parameters before and after administration of MgSO₄ was more in the middle cerebral artery than in the umbilical artery. Conclusion: Intravenous administration of magnesium sulfate in pregnant women with severe preeclampsia resulted in a decrease in umbilical artery, uterine artery, and fetal middle cerebral artery Doppler indices with reduced resistance to blood flow in these vessels.     

Effect of epidural anesthesia for cesarean delivery on maternal femoral arterial and venous, uteroplacental, and umbilical blood flow velocities and waveforms

The effect of epidural anesthesia on the maternal femoral arterial and venous, uteroplacental, and umbilical circulations was studied by the pulsed Doppler technique in 13 women undergoing elective cesarean delivery. Resistance and pulsatility indices of umbilical arterial velocity waveforms did not change with the use of epidural anesthesia. In the uteroplacental circulation, these indices increased in 11 patients, suggesting an increase in resistance. Reduction of sympathetic tone in resistance and capacitance vessels was reflected in the femoral artery by an increase in systolic and end-diastolic velocities, a reversal of the post-systolic backward flow, and an increase in mean velocity. The latter also occurred in the femoral vein. The diameters of these large maternal vessels did not change. This study suggests an impairment in uteroplacental circulation associated with a drop in peripheral vascular resistance and an increase in leg blood flow after epidural anesthesia.     

Uteroplacental Circulation Development: Doppler Assessment and Clinical Importance

In the first weeks of pregnancy, columns of endovascular cytotrophoblastic plugs develop in the lumen of spiral arteries. Morphologic data show that these plugs become loosened as soon as the end of the second month and the intervillous circulation of maternal blood is likely to be established progressively between the 8th and 12th weeks. The disorganization of the musculo-elastic layers of these vessels provokes a dramatic decrease in vascular tone in the uteroplacental circulation. These modifications appear to govern the establishment of a low-pressure blood flow in the placenta, and hence determine the quality of uteroplacental circulation and normal fetal growth. Placental bed biopsies in women with pre-eclampsia and in a proportion of pregnancies with intrauterine growth retardation have shown that these physiologic changes were absent in the myometrial segments of spiral arteries. Recently, colour Doppler was used to assess intervillous and spiral artery flow in early pregnancy, confirming in vivo free intervillous flow at 12 weeks and a progressive significant decrease in spiral artery resistance with advancing gestation during the first trimester. However, certain data at an earlier gestational age are still contradictory. Particularly, the exact nature of the contents of the intervillous space before 8 weeks, and whether or not this fluid can be considered maternal blood, remains controversial.     

Can umbilical artery Doppler findings at 36 weeks’ gestation predict maternal hypertension at later gestation?

Objectives: To clarify whether ultrasonographic evaluations of fetoplacental underperfusion using umbilical artery (UmA) Doppler indices at 36 weeks’ gestation can predict maternal hypertension at later gestation.

Methods: Normotensive pregnant women who underwent an ultrasound scan at 36 weeks’ gestation and delivered singleton infants at term between 2012 and 2013 were prospectively enrolled. UmA Doppler and maternal blood pressure results at 36 weeks’ gestation in cases with pregnancy-induced hypertension (PIH) at later gestation were compared with a control group.

Results: Thirty-nine and 775 cases were classified into the PIH and control group, respectively. The UmA pulsatility index (PI) and maternal systolic blood pressure (SBP) at 36 weeks’ gestation were higher in the PIH group than in control group (UmA-PI: 0.88 vs. 0.80, p?=?0.002; SBP: 126?mmHg vs. 112?mmHg, p?Conclusions: An increased UmA-PI at 36 weeks’ gestation is associated with the occurrence of PIH at later gestation. This result may indicate the possibility to detect fetoplacental underperfusion ultrasonically.     

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.