Fetal Doppler: umbilical artery, middle cerebral artery, and venous system

One of the most important applications of Doppler ultrasonography in obstetrics is the detection of fetal anemia in pregnancies complicated by either red-cell alloimmunization or by other causes of fetal anemia. Doppler of the umbilical artery also has prognostic value in pregnancies affected by twin-twin transfusion syndrome undergoing in-utero intervention. Another potential major application is the use of Doppler ultrasound in the management of intrauterine-growth-restricted fetuses. At the present time, there is no single test that appears superior to the other available tests for timing the delivery of the growth-restricted fetus. Therefore, the decision to deliver a fetus, especially at <32 weeks, remains mostly based on empirical management. Doppler may provide a more reliable and systematic basis for timing these deliveries. This review emphasizes the three following concepts: (a) normal and abnormal Doppler of the umbilical artery, middle cerebral artery, mitral and tricuspid valves, umbilical vein, and ductus venosus; (b) some clinical applications of Doppler sonography in obstetrics; and (c) potential future research of Doppler in obstetrics.     

Outcome of monochorionic twin pregnancies with abnormal umbilical artery Doppler between 16 and 20 weeks of gestation

Objectives.?To study the perinatal outcome among monochorionic diamniotic (MCDA) twin pregnancies with absent or reversed end-diastolic flow of the umbilical artery (UA-AREDF) at 16–20 weeks of gestation.

Methods.?This was a retrospective study of 84 MCDA twin pregnancies, which were followed up since first trimester in a single obstetric unit. Pregnancies with fetal structural anomalies or genetic syndromes, and those with single intrauterine death before 16 weeks were excluded. The study group was divided into four groups based on the finding of UA-AREDF at the routine follow-up scan at 16–20 week, and the presence of complications at the same time of recruitment. The perinatal outcome between these groups was compared.

Results.?AREDF was present in 56.7% of the 30 monochorionic (MC) twins with complications at recruitment. The mortality was significantly higher among those with AREDF. Among the 54 uncomplicated cases at recruitment, only 7.41% had AREDF. The presence of isolated AREDF was associated with significantly higher incidence of growth discordance (25.0% vs. 2%). The incidence of perinatal mortality and twin-to-twin transfusion syndrome was almost doubled (25.0% vs. 9% and 25.0% vs. 14%).

Conclusions.?AREDF of the umbilical artery is uncommon in normal MC twin in mid-trimester. Once AREDF is present, the perinatal outcome is much worse. Doppler assessment of the umbilical artery should be considered in all MC twin pregnancies for risk assessment.     

Prediction of perinatal outcome in preeclampsia using middle cerebral artery and umbilical artery pulsatility and resistance indices

Objective: In preeclampsia, changes in fetal hemodynamics can be detected 2–3 weeks earlier than any changes in cardiotocogram. Thus, these Doppler changes can be used to predict perinatal outcome. The present study is planned to assess the accuracy of the middle cerebral artery to umbilical artery (UA) pulsatility index (PI) and resistance index (RI) in predicting adverse perinatal outcome in pregnancies complicated by preeclampsia. Methods: Total of 115 and 108 pregnant women were included in preeclampsia and control group, respectively. Weekly Doppler study was done in both groups starting from 30 weeks till 36 weeks or delivery, whichever is later. Results: Mean gestational age at delivery was 250 ± 13 and 273 ± 8 days, respectively, in preeclampsia and control group (p < 0.01). Thirty-four babies in preeclampsia group had been admitted to nursery; out of which three died (p < 0.01). On receiver operating characteristic analysis, MCA /UmA PI ratio and MCA /UmA RI ratio had sensitivity of 9% and 9.7% and specificity of 98% and 96.6%, respectively, for predicting adverse perinatal outcome. Conclusion: Doppler indices of MCA and Um A are significantly abnormal in preeclampsia. But on diagnostic statistical analysis they have good specificity but low sensitivity for detecting adverse perinatal outcome.     

Abnormal Doppler velocimetry is related to adverse perinatal outcome for borderline amniotic fluid index during third trimester

AIM: To evaluate the relationship between abnormal Doppler velocimetry and adverse perinatal outcomes in pregnancies with borderline amniotic fluid index (AFI). METHODS: Medical records of 3740 pregnancies with known AFI and Doppler velocimetry measurements within 2 weeks of delivery, and delivered between January 1996 and December 2003, were retrospectively analyzed. Borderline AFI was defined as 5 cm < AFI < or = 8 cm. For the umbilical artery, Doppler velocimetry was considered abnormal when the S/D ratio was greater than 3.0 or when end-diastolic flow was absent; whereas, for the uterine artery, the S/D ratio was greater than 2.6 or presence of end-systolic notch was defined as abnormal. Adverse perinatal outcomes (small for gestational age, cesarean section for fetal distress, 5 min Apgar score of less than 7, respiratory distress syndrome, NICU admission, and perinatal death) according to Doppler velocimetry in borderline AFI were evaluated. RESULTS: Compared to the normal AFI group (n = 3523), the borderline AFI group (n = 217) had significantly higher incidence of adverse perinatal outcome (28.8% vs 54.8%). There was 3-fold increase in the incidence of adverse perinatal outcome among women with the borderline AFI in comparison to normal AFI (OR, 3.00; CI, 2.27-4.00). When abnormal Doppler velocimetry was associated with borderline AFI, a 5-fold increase in the incidence of adverse perinatal outcome was noted (OR, 5.26; CI, 3.00-9.21). CONCLUSION: In the borderline AFI group, the presence of abnormal Doppler velocimetry measurement was related to increased risk of adverse perinatal outcome. Thus, borderline AFI of 5-8 cm, especially when associated with abnormal Doppler velocimetry, mandates closer antenatal surveillance.     

Prediction of perinatal outcome by middle cerebral artery doppler velocimetry

The relationship between pulsatility index (PI) in the middle cerebral artery (MCA) and adverse perinatal outcome was studied in 162 normal and 75 high-risk pregnancies. The intrapartum cardiotocographic (CTG) findings, the mode of delivery, 1 and 5-minute Apgar scores, the pH level of the umbilical artery, admission to the neonatal intensive care unit (NICU) and the incidence of intrauterine fetal growth retardation were recorded. In the low risk group, the PI values in the MCA were only affected in growth retarded fetuses (P = 0.0084). In the high-risk group, there was an association between the MCA PI values and 5-minute Apgar scores (P = 0.0397), umbilical artery pH values (P = 0.0068) and development of IUGR (P = 0.0376). In both groups, an abnormal intrapartum CTG, the 1-minute Apgar score, cesarean section for fetal distress and admission to the NICU were not related to PI values in the MCA. Our present study suggests that doppler flow measurement of MCA provides useful information about perinatal outcome, especially in the high-risk pregnancies. Received: 19 January 1995 / Accepted: 5 February 1996     

Effects of oral L-arginine on the pulsatility indices of umbilical artery and middle cerebral artery in preterm labor

OBJECTIVE: The objective of the study was the estimation of the influence of oral supplementation with low-dose l-arginine on feto-placental circulation in women with threatened preterm labor. STUDY DESIGN: Oral administration of 3g of L-arginine daily or placebo as a supplement to standard tocolytic therapy was tried in 70 women with threatened preterm delivery, randomly assigned to the L-arginine (n=37) or placebo (n=33) groups. Twenty-five and 20 completed the study, respectively. Doppler velocimetry of pulsatility indices (PI) of the umbilical (UA) and middle cerebral (MCA) arteries as well as pregnancy outcome and biochemical markers of nitric oxide synthesis (plasma amino acid and nitrite/nitrate levels, as well as 24 h nitrite/nitrate excretion with urine) were estimated. RESULTS: Starting from the second week of therapy, the UA PI values were significantly lower in the L-arginine group than in the placebo group. Moreover, treatment with L-arginine caused a significant increase in MCA PI and cerebro-placental ratio (CPR) values. The changes in feto-placental circulation in the L-arginine group were not associated with any signs of increased nitric oxide synthesis. CONCLUSION: Oral supplementation with low doses of L-arginine changed feto-placental blood flow distribution in patients with threatened preterm labor. The exact mechanism of L-arginine action on feto-placental circulation requires further investigation.     

Use of umbilical artery Doppler velocimetry in the monitoring of pregnancy in women with pre-existing diabetes

BACKGROUND: The usefulness of umbilical artery Doppler velocimetry for the monitoring of diabetic pregnancies is controversial. The aim of the present study was to assess whether umbilical artery Doppler velocity waveform analysis can predict adverse perinatal outcomes for pregnancies complicated by pre-existing diabetes mellitus. METHODS: All diabetic pregnancies (type 1 and 2) delivered at Mater Mothers' Hospital, Queensland, between 1 January 1995 and 31 December 1999 were included. All pregnant diabetic women were monitored with umbilical artery Doppler velocimetry at 28, 32, 36, and 38 weeks' gestation. Adverse perinatal outcome was defined as pregnancies with one or more of the following: small-for-gestational age, Caesarean section for non-reassuring cardiotocography, fetal acidaemia at delivery, 1-min Apgar of 3 or less, 5-min Apgar of less than 7, hypoxic ischaemic encephalopathy or perinatal death. Abnormal umbilical artery Doppler velocimetry was defined as a pulsatility index of 95th centile or higher for gestation. RESULTS: One hundred and four pregnancies in women with pre-existing diabetes had umbilical arterial Doppler studies carried out during the study period. Twenty-three pregnancies (22.1%) had an elevated pulsatility index. If the scans were carried out within 2 weeks of delivery, 71% of pregnancies with abnormal umbilical Doppler had adverse outcomes (P < 0.01; likelihood ratio, 4.2). However, the sensitivity was 35%; specificity was 94%; positive predictive value was 80%; and negative predictive value was 68%. Only 30% of women with adverse perinatal outcomes had abnormal umbilical arterial Doppler flow. CONCLUSION: Umbilical artery Doppler velocimetry is not a good predictor of adverse perinatal outcomes in diabetic pregnancies.     

Small for gestational age preterm infants and relationship of abnormal umbilical artery Doppler blood flow to perinatal mortality and neurodevelopmental outcomes

Aim: To determine the outcomes of preterm small for gestational age (SGA) infants with abnormal umbilical artery (UA) Doppler studies.
Methods: A retrospective cohort study of SGA singleton infants delivered between 24 and 32 weeks gestation at King Edward Memorial Hospital, Perth, who had UA Doppler studies performed within seven days of birth. Main outcomes assessed were perinatal mortality and morbidity, and neurodevelopmental outcomes at ≥ 1 year of age. Outcomes were compared by normality of UA blood flow.
Results: There were 119 infants in the study: 49 (41%) had normal UA Doppler studies, 31 (26%) had an increased systolic–diastolic ratio ≥ 95th centile, 19 (16%) had absent end diastolic blood flow (AEDF) and 20 (17%) had reversed end-diastolic flow (REDF). Infants in the AEDF and REDF groups were delivered significantly more preterm ( P  = 0.006) and had lower birthweights ( P  < 0.001). Ninety four per cent (110 of 117) of live born infants survived. Neurodevelopmental follow-up at 12 months of age or more (median 24 months) was available on 87 of 108 (81%) of live children. Twenty-eight per cent (11 of 39) of fetuses who had had AEDF or REDF died or were classified with moderate or severe disability. There was no significant association between abnormality of UA blood flow, perinatal morbidity, perinatal mortality and neurodevelopmental disability after correction for gestational age.
Conclusion: Fetuses that are SGA with abnormal UA Doppler studies remain at significant risk of perinatal death, perinatal morbidity and long-term neurodevelopmental disability, associated with their increased risk of preterm birth.     

Uterine and umbilical artery Doppler are comparable in predicting perinatal outcome of growth-restricted fetuses

Objective  To compare umbilical and uterine artery Doppler in predicting outcome of pregnancies suspected of fetal growth restriction (FGR).
Design  A prospective study included 353 singleton pregnancies complicated by an FGR fetus.
Setting  University Hospital setting.
Sample  Pregnancies suspected of FGR diagnosed by ultrasound fetal biometry during a 5-year period.
Main outcome measure  Perinatal outcome in relation to uterine and umbilical artery Doppler.
Methods  The women underwent Doppler examination of the umbilical and uterine arteries. Results from the uterine, but not the umbilical artery, were blind to the woman and managing obstetrician. The Doppler results were related to perinatal outcomes including small for gestational age newborns, caesarean delivery, premature delivery (<37 weeks of gestation) and admission of the newborn to a neonatal intensive care unit.
Results  Abnormal uterine artery Doppler velocimetry was seen in 120 (33.4%) pregnancies and abnormal umbilical artery Doppler in 102 (28.4%). There was a statistically significant correlation between abnormal Doppler of both the umbilical and uterine arteries and adverse outcome of pregnancy. The two vessels were comparable in predicting adverse outcome. Women with normal umbilical artery Doppler (251) were analysed separately. Abnormal uterine artery Doppler, seen in 61 (24.3%) of those women, showed a statistically significant correlation for adverse outcome of pregnancy.
Conclusions  Doppler examinations of the uterine and/or the umbilical arteries seem to be comparable as predictors of outcome in pregnancies complicated by FGR. Including uterine artery Doppler in the surveillance of growth-restricted fetuses might detect a group of pregnancies at high risk, even though the umbilical artery Doppler was normal.     

Amniotic fluid index measurements in normal pregnancy after 28 gestational weeks.

OBJECTIVE: The purpose of this study is to establish a normative scale of amniotic fluid index (AFI) or four-quadrant amniotic fluid index throughout gestation in uncomplicated singleton pregnancies, and to identify the lower and upper limits for each gestational week. METHOD: A prospective longitudinal study was used. One hundred seventeen uncomplicated singleton pregnancies were examined every 4 weeks between 28 and 42 week's gestation. The uterine cavity was divided into four quadrants. With the use of linear-array, real-time B-scanning, the vertical diameter of the largest pocket in each quadrant was measured. The amniotic fluid index is the sum of these four quadrants. RESULTS: The amniotic fluid index observations from regression equation curve were stratified in week-specific normative curves. The variation between mean AFI of the total population and the means of the preterm was significantly greater than term pregnancies (P<. 05). The AFI 2.5%, 5%, 10%, 90% 95% and 97.5% limits about the 50th (124 mm) were 68, 81, 90, 135, 144 and 145 mm, respectively, in term gestation. The 5th and 95th percentile serves as lower and upper limits of normal, respectively for 28-42 weeks gestation. CONCLUSIONS: Gestational age-specific values of AFI were established, determining the significant trends of changes in the amniotic fluid volume with gestation. The normogram may have a clinical benefit to accurate, reliable and semiquantitative diagnosis of oligohydramnios and polyhydramnios.     

Doppler blood flow velocity waveforms in the fetal renal artery

Summary In 19 out of 20 human fetuses we recorded blood velocity waveforms in the renal artery by means of a duplex Doppler sector scanner. One fetus was at 22 weeks gestation, 7 fetuses were between 32 and 35 weeks, and 12 fetuses between 36 and 40 weeks. There was no evidence of intrauterine growth retardation and there was a normal quantity of amniotic fluid in all pregnancies. We also recorded waveforms in the umbilical artery, the descending aorta, and the internal carotid artery. The RI in these vessels showed normal values in all cases. There was no end-diastolic flow in four of the seven fetuses studied at 32 to 35 weeks gestation. The mean RI of fetuses with end-diastolic flow was 0.86 (SD 0.03). The interpretations of these results, and ideas for future studies are discussed.     

Fetal cerebral and umbilical Doppler in pregnancies complicated by late-onset placental abruption

Objective: To evaluate whether changes in the cerebroplacental Doppler and birth weight (BW) suggestive of chronic fetal hypoxemia, precede the development of late-onset placental abruption (PA) after 32 weeks.

Methods: In a multicenter retrospective study, the Doppler examinations of the fetal umbilical artery (UA) and middle cerebral artery (MCA) recorded after 32 weeks were collected in pregnancies subsequently developing PA. The BW centiles were calculated and the MCA pulsatility indices (PI), and UA PI were converted into multiples of the median (MoM). Afterwards, a comparison was made with a group of fetuses, which did not develop PA. Logistic regression was used to adjust for potential confounders and evaluate the feasibility of the prediction model.

Results: Pregnancies complicated by late-onset PA (n?=?31) presented lower MCA PI (p?=?0.015) and were smaller (p?n?=?1294). Logistic regression analysis indicated that cerebral vasodilation was more important than umbilical flow in the explanation of PA (MCA PI OR?=?0.106, p?=?0.014 and UA PI OR 1.901, p?=?0.32). In addition, the influence of BW exerted was residual (BW centile OR?=?0.989, p?=?0.15).

Conclusions: Fetuses developing late-onset PA demonstrate significant cerebral vasodilation with scarce placental dysfunction, suggesting the existence of some kind of chronic hypoxemia that follows the late-onset pattern.     

Maternal,fetal and perinatal characteristics of preeclampsia cases with and without abnormalities in uterine artery Doppler indexes

Abstract

Objective: To compare the maternal and fetal characteristics and perinatal outcome in mild and severe preeclampsia cases with and without uterine artery Doppler abnormalities.

Methods: Two hundred and fifty-nine mild and severe preeclampsia cases were evaluated retrospectively. Doppler measurements were done in the section where uterine artery raised from the hypogastric artery. Pulsatility index above the 95th percentile of the corresponding gestational age was accepted as abnormal.

Results: In mild and severe preeclampsia cases with abnormal Doppler (AD), the rate of intrauterine growth restriction, preterm birth and low birth weight was higher than, but the neonatal intensive care unit stay was similar to the cases with normal Doppler. Base excess was higher in the AD group, in mild and severe preeclampsia. The rate of low Apgar score at 5?min and perinatal mortality was higher in the AD group, in the mild preeclampsia. The strongest independent predictor of the perinatal morbidity and mortality was the presence of prematurity and of the prematurity was the presence of abnormal uterine artery Doppler.

Conclusions: Maternal and perinatal morbidity and perinatal mortality increase in mild to severe preeclampsia cases with abnormal uterine artery Doppler. The abnormal uterine artery Doppler increases the morbidity and mortality by increasing the risk of prematurity.     

脐血流测定对脐带绕颈的产时监护

目的 :研究脐血流测定对脐带绕颈的产时监护作用。方法 :对 5 5 0例单胎足月妊娠孕妇进行脐血流测定 ,其中脐带绕颈 138例。分A、B、C 3组 ,分析其产时胎儿宫内窘迫发生率 (简称 :胎窘率 )及剖宫产率 ,并动态观察 14 0例(其中脐带绕颈 5 2例 ,无绕颈 88例 )产妇 ,产程中的脐血流变化。结果 :3组脐带长度、绕颈周数、新生儿Apgar评分 ,差异无显著性 (P >0 0 5 )。B组与C组的产时胎窘率及剖宫产率均较A组高 (P <0 0 1,P <0 0 5 )。产程中 ,S/D升高 >0 1,有脐带绕颈组明显高于无绕颈组 (P <0 0 1) ,S/D >3 0与 2 70 相似文献   

Fetal umbilical arterial and venous Doppler measurements in gestational diabetic and nondiabetic pregnancies near term

Objective.?To compare Doppler measurements of umbilical arteries (UAs) and veins (UV) in diabetic and nondiabetic pregnancies near term.

Methods.?Consecutive patients with gestational diabetes mellitus (GDM) were prospectively recruited from a regional obstetric service over an 18-month period. Doppler assessment of the UA and UV done within 10 days from delivery were used for analysis. Similar measurements were performed in a control group of nondiabetic nonhypertensive patients near term.

Results.?All of the Doppler waveform patterns were within normal in the cohort of 140 patients (GDM 84, normal 62). The mean PI values for the UA and the mean total umbilical venous flow (TUVF) and TUVF per unit birth weight did not differ significantly between diabetic and nondiabetic pregnancies. Large-for-gestational-age fetuses showed higher TUVF than normal size fetuses, but the TUVF per unit birth weight was higher for small-gestational-age fetuses. These differences were independent of their diabetic status.

Conclusion.?Umbilical arterial and venous Doppler measurements near term were unable to distinguish between diabetic and nondiabetic pregnancies. Umbilical venous flow volume was apparently more sensitive to the size of the fetus than to the maternal diabetic state.     

Prediction of fetal anemia by middle cerebral artery Doppler

ObjectivesTo assess the value of peak systolic velocity in the middle cerebral artery (MCA) in prediction of fetal anemia as a non invasive method in non hydropic fetuses.MethodsThe study included 30 pregnant women with non hydropic fetuses and with known red cell antibodies. Full ultrasound examination was done and peak velocity of systolic cerebral blood flow in MCA was measured. If severe anemia was suspected, fetal blood sampling by cordocentesis was performed.ResultsThirty fetuses were examined, 22 were anemic and eight had a hemoglobin value within a normal range. The mean MCA peak systolic velocity for fetus with the normal hemoglobin (Hb) was 48.98 ± 13.94 while that for the anemic fetus was 64.79 ± 11.97 and P = 0.004.Sensitivity of increased peak velocity of systolic blood flow in MCA for prediction of fetal anemia was 90.5% and specificity was 78.6%.ConclusionDoppler of peak velocity of systolic blood flow in MCA can be reliable in predicting anemia so delaying invasive methods until treatment (blood transfusion) is expected to be necessary.     

Betamethasone effects on umbilical arteries and ductus venosus Doppler velocity waveforms in growth-restricted fetuses

We studied intrauterine-growth-restricted (IUGR) fetuses with absent or reversed umbilical artery end-diastolic flow (EDF) velocity in order to evaluate the benefit of antenatal steroid therapy. Perinatal outcomes after betamethasone were evaluated where end diastolic flow returned (group I), compared with data from fetuses with persistent absent-reverse end diastolic(ARED) flow (group II). Objectives/methods: We recruited sixty-four IUGR fetuses, 28–32 weeks’ gestation, whose umbilical artery spectral tracings showed ARED flow and positive a-wave in the ductus venosus at admission. Results: Group I, 21 cases of restored EDF after betamethasone: Significant, persistent return of umbilical artery EDF flow and persistent ductus venosus a-wave were documented. Group II, 43 cases of persistent ARED flow: Persistent ARED flow in umbilical arteries and deterioration of ductus venosus waveform with significant, increasing pulsatility index and/or a-wave disappearance were documented. In group I, cardiotocographic alterations were delayed contrasted with group II, (p?=?0.03). Neonatal complications in group II were eight cases of intraventricular hemorrhage; two cases of retinopathy of prematurity; three neonatal deaths, one fetal demise; and a higher incidence of neonatal respiratory distress syndrome. Conclusions: Betamethasone treatment may have beneficial effects on restoring end-diastolic umbilical artery velocimetry and precordial waveforms. These spectral Doppler changes are related to delayed cardiotocographic alterations and to better perinatal outcomes.     

Prognostic value of umbilical-middle cerebral artery pulsatility index ratio in fetuses with growth restriction.

OBJECTIVE: To study the utility of Doppler velocimetry and computerized cardiotocography in the management of intrauterine growth restriction and prediction of neonatal outcome. PATIENTS AND METHODS: Seventy-two pregnant women with fetuses showing growth restriction and delivered within 48 h of their last Doppler velocimetry evaluation. The last computerized cardiotocographic trace from these fetuses was used for statistical analysis, and the last trace from the healthy fetuses of 93 consecutive women undergoing cesarean section was used as control. Umbilical artery pulsatility index (UA PI), middle cerebral artery pulsatility index (MCA PI), UA PI/MCA PI ratio, and uterine artery resistance index (Ut RI) were assessed. RESULTS: Among women with growth-restricted fetuses, all parameters were significantly higher in those who had hypertension; and in those who had diabetes, only the UA PI/MCA ratio was significantly higher. Umbilical artery PI values and the UA PI/MCA ratio were higher in those who had a nonreassuring result to computerized nonstress test immediately before delivery. A multiple logistic analysis showed that the UA PI/MCA ratio was the only Doppler velocimetry parameter predicting cardiotocographic nonreactivity; furthermore, the predictivity of extended newborn hospitalization (longer than 15 days) was verified, with a sensitivity of 56% and a specificity of 92% when the ratio was higher than 1.26. CONCLUSION: The MCA PI of fetuses with growth restriction should be assessed. The UA PI/MCA ratio is predictive of a nonreactive computerized cardiotocography trace and of prolonged neonatal hospitalization.     

Evaluation of fetal intrapartum hypoxia by middle cerebral and umbilical artery Doppler velocimetry with simultaneous cardiotocography and pulse oximetry

Objective To investigate fetal circulation at different stages of hypoxia during labor, and to study blood flow alterations in the brain and peripheral tissues, through simultaneous use of three non-invasive techniques.Materials and methods Ninety two pregnant women between 38 and 41 weeks of gestation, comparable for maternal age and parity, were simultaneously monitored with cardiotocography (CTG), continuous fetal pulse oximetry and Doppler ultrasonography during the first stage of labor. In 70 cases evaluation was successful, and useful data was obtained. Doppler waveforms were obtained before and during abnormal CTG patterns, of both the umbilical (UA) and middle cerebral artery (MCA) to measure the pulsatility index (PI), resistance index (RI), and flow velocity integral (FVI). The study population was divided in three groups, according to CTG and fetal pulse oximetry tracings: 20 term fetuses with normal CTG patterns and oxygen saturation (FSPO₂) values >40%, 30 term fetuses with abnormal CTG patterns and FSPO₂ values between 30 and 40%, and 20 fetuses with abnormal CTG patterns and FSPO₂ values <30% for a time up to 2 min. These were studied and peripartum outcomes were compared.Results Redistribution of blood flow was noted at FSPO₂ values of 37%, in all groups. In the presence of reduced oxygen saturation (near to or below 30%), MCA Doppler showed significantly lower PI (1.06±0.33 vs.0.74±0.39, p=0.03) and RI (0.59±0.14 vs. 0.44±0.14, p=0.03), while that of the UA showed mildly higher resistance indices (0.98±0.14 vs. 1.28±0.50, p=0.01 and 0.57±0.12 vs. 0.79±0.24, p=0.004, respectively). When an oxygen saturation value of <30% was maintained for greater than 2 min, MCA Doppler indices reversed, likely indicating morbid fetal hypoxia. Differences in fetal outcomes between groups correlated with Doppler and pulse oximetry tracings.Conclusions During active labor the fetus maintains oxygen supply to the brain by redistributing blood flow. In cases of hypoxia this is feasible for only 2 min. We note a strong correlation between fetal pulse oximetry, Doppler velocimetry of the MCA and UA, and fetal morbidity.