The role of Doppler and placental screening

Ultrasound Microvessel Imaging of the Human Placenta Demonstrates Altered Vessel Densities in Fetal Growth Restriction With Vascular and Immune Pathologies: A Pilot Case-Control Study

OBJECTIVES

Fetal growth restriction (FGR) is commonly associated with placental dysfunction, increasing perinatal morbidity and mortality. Visualizing placental vessels in utero would be advantageous for identifying functional FGR cause and determining proper management strategies. We aimed to utilize high-sensitivity ultrasound microvessel imaging (HUMI) for quantifying placental vessel density (VD) in pregnancies diagnosed with FGR.

METHODS

This pilot case-control study enrolled subjects in the third trimester with a diagnosis of FGR (n = 40) and gestational age-matched controls with normal fetal growth (n = 20) at a 2:1 ratio, respectively. The Verasonics Vantage ultrasound system was used to perform HUMI on each participant at one timepoint. Scanning involved randomized singular value decomposition-based clutter filtering to identify the villous tree, followed by step-by-step scanning to acquire 3-dimensional-like data. Mean VD was calculated from three ultrasound measurements per subject. Additional clinical and pathology data were also collected and compared.

RESULTS

Sixteen participants were utilized to establish the scanning protocol and 2 met exclusion criteria at delivery. Thus, VD was successfully measured on 42 pregnancies scanned at 35 weeks 5 days on average. In FGR (n = 24), placental VD was significantly reduced compared to controls (P < .01). VD measures were as good at predicting FGR as systolic/diastolic (S/D) ratios (area under the curve 0.86 versus 0.80). In a smaller cohort, VD in placentas with a diagnosis of inflammatory villitis (n = 10) by histology showed an increase in VD compared to those without inflammation (P = .01). Low VD was correlated with increased S/D ratios (P = .03).

CONCLUSIONS

HUMI is useful for identifying altered placental vascularization in utero for FGR. VD may be a valuable indicator for placental health and could lead to improved risk stratification methods considering underlying biology.

Second systolic peak in fetal middle cerebral artery Doppler after intrauterine transfusion

OBJECTIVE

To evaluate functional relationship between fetal circulatory response to intrauterine transfusion (IUT) as a circulatory challenge and appearance of second systolic peak (P2) in middle cerebral artery (MCA) based on hemodynamic principles.

METHODS

According to the concept of pulse wave (PW) propagation and reflection in adults, PWs arrive twice at cerebral circulation, as primary wave caused by left ventricle ejection and secondary after reflection in peripheral arteries. Thus adults show a biphasic contour of systolic blood flow in cerebral arteries. Similar waveforms may appear in fetal MCA-Doppler, as a response to IUT as a circulatory challenge. This is a proof-of-principle study, applying classical hemodynamic principles to fetal circulation. Accordingly, appearance of MCA-P2 may indicate vasoconstriction with increased PW reflection and timing of P2(Δt) should agree with the additional PW travel time down to reflection and return (Tr). To test this agreement, we searched our database for IUTs performed for severe fetal anemia, and compared Δt, obtained by Doppler, with Tr, obtained by hemodynamic calculation using human fetal data. Level of agreement was assessed using Bland-Altman-Plots.

RESULTS

We identified 21 fetuses with adequate Doppler quality for Δt evaluation. In four cases (19%) MCA-P2 was observed before the intervention, and in 17 interventions (81%) thereafter; a highly significant association between IUT and P2 appearance (p < 0.001). In these 17 interventions good agreement of P2 timing was found between Doppler assessment: Δt = 80 ± 8 ms, and hemodynamic calculation: Tr = 76 ± 4 ms.

CONCLUSION

P2 appearance in fetal MCA-Doppler seems to indicate PW reflection due to increased vasoconstriction after IUT. Thus hemodynamic considerations might enable Doppler monitoring of fetal vasoconstriction.

Doppler changes in umbilical artery, middle cerebral artery, cerebroplacental ratio and ductus venosus during open fetal microneurosurgery for intrauterine open spina bifida repair

OBJECTIVE

To describe changes in fetal Doppler parameters during a novel technique for open fetal microneurosurgery for open spina bifida (OSB) repair.

METHODS

This was a prospective study of 44 fetuses undergoing open fetal surgery for OSB repair using a novel microneurosurgery approach that is characterized by a mini-hysterotomy (diameter of 15 mm), minimal fetal manipulation and maintenance of a constant normal amniotic fluid volume throughout the procedure. Doppler velocimetry of the umbilical artery (UA), fetal middle cerebral artery (MCA) and ductus venosus (DV) was performed before the start of surgery and at prespecified timepoints during fetal surgery. UA pulsatility index (PI) > 95^th percentile, DV-PI > 95^th percentile, MCA-PI < 5^th percentile and cerebroplacental ratio (CPR) < 5^th percentile were considered abnormal.

RESULTS

Median gestational age at fetal surgery was 25.2 weeks (range, 22.9-27.9 weeks). Doppler recordings were successfully obtained in all cases during all timepoints throughout the surgery. As compared with Doppler values before surgery, there was a significant increase in the proportion of fetuses with MCA-PI < 5^th percentile (63.6% vs 13.6%; P < 0.001), CPR < 5^th percentile (65.9% vs 15.9%; P < 0.001) and DV-PI > 95^th percentile (22.7% vs 0%; P = 0.01) and a non-significant increase in the proportion of fetuses with UA-PI > 95^th percentile (11.4% vs 0%; P = 0.12) during fetal surgery. None of the fetuses showed absent or reversed end-diastolic velocity in the UA or absent or reversed DV a-wave at any stage during OSB repair. All abnormal Doppler parameters returned to normal after surgery.

CONCLUSIONS

During open fetal surgery for OSB repair, a small hysterotomy, reduced fetal manipulation and maintenance of a normal amniotic fluid volume seem to prevent severe fetal Doppler abnormalities. The mild Doppler changes observed during fetal surgery could be a manifestation of fetal adaptation to the stress of fetal surgery. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

Doppler studies of placental function

Placental-associated diseases account for most cases of adverse perinatal outcome in developing countries. Doppler evaluation has been incorporated as a predictive parameter at early pregnancy for high-risk placental disease, in the diagnosis and management of those fetuses with impaired intrauterine growth and for the evaluation of fetal wellbeing in those high-risk pregnancies. Uterine Doppler at second trimester predicts most instances of early-onset preeclampsia and intrauterine growth restriction. However, the growing evidence of an effective early propylactic strategy, has turned Uterine Doppler an essential parameter to be included in first trimester predictive algorithms. Umbilical artery Doppler helps in the identification of small-for-gestational-age fetuses at higher risk, and is one of the essential vessels in the assessment of fetal hypoxia impairment, especially in the early cases. It helps in the decision timing for ending the pregnancy improving thus perinatal outcomes. Moreover, in high-risk pregnancies, umbilical artery Doppler has demonstrated to reduce the risk of perinatal deaths and the risk of obstetric interventions. On the other hand, middle cerebral artery Doppler reflects fetal adaptation to hypoxia, and with the cerebroplacental ratio, they improve the detection of fetuses a high risk of adverse perinatal outcome, mostly of those late small fetuses, where most instances of adverse outcome occur in fetuses with normal umbilical artery. Ductus venosous Doppler waveform is a surrogate parameter of the fetal base-acid status. Its use has demonstrated to improve perinatal outcomes, mainly reducing the risk of fetal intrauterine death. Alone or in combination with computerized CTG, it helps tailoring the best moment to end the pregnancy among early cases.

A low fetal cerebroplacental ratio confers a greater risk of intrapartum fetal compromise and adverse neonatal outcomes in low risk multiparous women at term

BACKGROUND

A low fetal cerebroplacental ratio (CPR) and nulliparity have independently been shown to be associated with adverse obstetric and perinatal outcomes.

OBJECTIVES

To assess the effect of parity on the CPR and investigate the utility of a CPR threshold of <10^th centile for predicting adverse outcomes. We hypothesised that nulliparous women would have a lower CPR than multiparous women, impacting the diagnostic performance of the <10^th centile threshold. This is an important consideration for interpretation of a low CPR in clinical practice.

STUDY DESIGN

This was a retrospective cohort study of low risk, singleton pregnancies delivering at term in Australia's largest maternity hospital. The primary outcome was emergency caesarean section for intrapartum fetal compromise (EmCS IFC). Data was dichotomised according to parity and further by CPR <10^th centile. Multiple logistic regression was performed.

RESULTS

4737 women were included for analysis, 2333 were nulliparous and 2404 were multiparous. Overall the z-score (mean [SD])(CPR standardised for gestation) was lower in nulliparous compared to multiparous women (-0.16 [-1.73 - 1.42] vs 0.04 [-1.63 - 1.69], p < 0.001). Multiparous women had a non-significantly lower mean z-score for those who delivered by EmCS IFC than nulliparous women (-0.52 [-2.23 - 2.02] vs -0.45 [-2.22 - 1.1]). Nulliparous women had greater odds of having a CPR <10^th centile compared to the multiparous cohort (OR 1.24, 95% CI 1.02-1.5 vs. OR 0.81, 95% CI 0.7-0.98, p < 0.001). A CPR thresholdd <10^th centile in nulliparous women was associated with increased odds of intrapartum fetal compromise (IFC), EmCS IFC (aOR 1.72, 95CI 1.2-2.6, p < 0.05) and birthweight <10^th centile. A low CPR in multiparous women was associated with increased odds of all adverse perinatal outcomes measured: IFC, meconium stained liquor, EmCS IFC (aOR 4.99, 95%CI 2.5-9.9, p < 0.001), birthweight <10^th centile, acidosis, neonatal intensive care admission and severe composite neonatal outcome. These aORs were associated with specificities of >90% and false positive rates of <10% for all outcomes in multiparous women.

CONCLUSIONS

A CPR <10^th centile in multiparous women confers greater odds of adverse perinatal outcomes and as such of the influence of parity should be taken into account when decisions regarding clinical management are made because of a low CPR.

Influence of fetal blood flow redistribution on fetal and childhood growth and fat distribution: the Generation R Study

OBJECTIVE

A suboptimal intrauterine environment leads to fetal blood flow redistribution and fetal growth restriction. Not much is known about childhood growth consequences. We examined the associations of fetal blood flow redistribution with birth outcomes, and repeatedly measured fetal and childhood growth and fat mass measures.

DESIGN

Prospective cohort study.

SETTING

Population-based.

POPULATION

One thousand one hundred and ninety-five pregnant women and their children.

METHODS

We measured umbilical and cerebral artery blood flow at a gestational age of 30.3 weeks (95% range, 28.5-32.6 weeks). A higher umbilical/cerebral (U/C) pulsatility index ratio is an indicator of preferential blood flow to the brain cerebral circulation at the expense of the lower body parts.

MAIN OUTCOME MEASURES

Fetal and childhood growth were repeatedly measured from the third trimester until childhood. We measured the total body fat mass, lean fat mass and android/gynoid fat mass ratio by dual-energy X-ray absorptiometry and preperitoneal fat by ultrasound at 6 years.

RESULTS

A higher fetal U/C ratio was associated with increased risks of preterm birth and small size for gestational age at birth [odds ratios, 1.41 (95% confidence interval, 1.08-1.85) and 1.63 (95% confidence interval, 1.21-2.19), respectively, per SDS increase in U/C ratio]. Longitudinal growth analyses showed that a higher fetal U/C ratio was associated with persistently lower head circumference, length and weight from third trimester fetal life until childhood (all P < 0.05). The fetal U/C ratio was not associated with total body and abdominal fat measures at 6 years.

CONCLUSION

Our results suggest that fetal blood flow redistribution affects fetal development and has persistent consequences for childhood growth.

TWEETABLE ABSTRACT

Fetal blood flow redistribution affects fetal development and has persistent consequences for childhood growth.

Preterm Birth Prevention: Effects of Vaginal Progesterone Administration on Blood Flow Impedance in Uterine-Fetal Circulation by Doppler Sonography

Objective:

The present study aimed to evaluate the effect of vaginal progesterone administration on maternal and fetal circulation to prevent preterm birth.

Methods:

The present prospective study was conducted on 35 women with singleton pregnancy at 18–33 weeks of gestation, who presented with at least one episode of preterm labor or asymptomatic short cervix, or past medical history of preterm birth. Doppler flow and Pulsatility Index (PI) assessment of the umbilical artery, fetal middle cerebral artery, uterine arteries, and ductusvenosus were performed before and 72 h after vaginal progesterone administration.

Results:

Results showed a significant reduction in the PI of the uterine artery following progesterone administration. Nevertheless, no significant changes were observed in the PI of other vessels. No significant difference was found in Doppler flow parameters in any of the examined vessels before or after progesterone treatment in women with Preterm Labor Pain (PLP). Yet, a statistically significant association was observed between short cervix complication in the current pregnancy and medical history of PLP in the previous pregnancy.

Conclusion:

Treatment with vaginal progesterone reduced the PI in the uterine arteries in the second and third trimesters of pregnancy. Thus, this medication may have useful vasodilatory effects on uterine-fetal vessels.

Fetal middle cerebral artery and umbilical artery pulsatility index: effects of maternal characteristics and medical history

OBJECTIVE

To define the contribution of maternal variables which influence the measured fetal middle cerebral artery (MCA) and umbilical artery (UA) pulsatility index (PI) in the assessment of fetal wellbeing.

METHODS

Maternal characteristics and medical history were recorded and fetal MCA-PI and UA-PI (n = 36,818) were measured in women with singleton pregnancies attending a routine hospital visit at 30 + 0 to 37 + 6 weeks' gestation. For pregnancies delivering phenotypically normal live births or stillbirths ≥ 30 weeks' gestation, variables among maternal demographic characteristics and medical history that are important in the prediction of MCA-PI and UA-PI were determined by multiple linear regression analysis.

RESULTS

Significant independent contributions to MCA-PI were provided by gestational age at assessment, East Asian racial origin, being parous and birth-weight Z-score of the neonate of the previous pregnancy. Significant independent contributions to UA-PI were provided by gestational age at assessment, Afro-Caribbean, East Asian and mixed racial origin, cigarette smoking, being parous and birth-weight Z-score of the neonate of the previous pregnancy. Multiple linear regression analysis was used to define the contribution of maternal variables that influence the measured MCA-PI and UA-PI and express the values as multiples of the median (MoMs). The cerebroplacental ratio (CPR) MoM was calculated by dividing MCA-PI MoM by UA-PI MoM. The model was shown to provide an adequate fit of MoM values for all covariates, both in pregnancies that delivered small-for-gestational-age neonates and in those without this pregnancy complication.

CONCLUSIONS

A model was fitted to express MCA-PI, UA-PI and CPR as MoMs after adjusting for variables from maternal characteristics and medical history that affect this measurement.

Expression profile of C19MC microRNAs in placental tissue in pregnancy-related complications

To demonstrate that pregnancy-related complications are associated with alterations in placental microRNA expression. Gene expression of 15 C19MC microRNAs (miR-512-5p, miR-515-5p, miR-516-5p, miR-517-5p, miR-518b, miR-518f-5p, miR-519a, miR-519d, miR-519e-5p, miR-520a-5p, miR-520h, miR-524-5p, miR-525, miR-526a, and miR-526b) was assessed in placental tissues, compared between groups (21 gestational hypertension [GH], 63 preeclampsia, 36 fetal growth restriction [FGR], and 42 normal pregnancies), and correlated with the severity of the disease with respect to clinical signs, delivery date, and Doppler ultrasound parameters. The expression profile of microRNAs was different between pregnancy-related complications and controls. The downregulation of 4 of 15 (miR-517-5p, miR-519d, miR-520a-5p, and miR-525), 6 of 15 (miR-517-5p, miR-518f-5p, miR-519a, miR-519d, miR-520a-5p, and miR-525), and 11 of 15 (miR-515-5p, miR-517-5p, miR-518b, miR-518f-5p, miR-519a, miR-519d, miR-520a-5p, miR-520h, miR-524-5p, miR-525, and miR-526a) microRNAs was associated with GH, FGR, and preeclampsia, respectively. Sudden onset of severe preeclampsia requiring immediate termination of gestation and mild forms of preeclampsia (persisting for several weeks) were associated with similar microRNA expression profile (downregulation of miR-517-5p, miR-520a-5p, miR-524-5p, and miR-525). In addition, miR-519a was found to be associated with severe preeclampsia. The longer the pregnancy-related disorder lasted, the more extensive was the downregulation of microRNAs (miR-515-5p, miR-518b, miR-518f-5p, miR-519d, and miR-520h). The downregulation of some C19MC microRNAs is a common phenomenon shared between GH, preeclampsia, and FGR. On the other hand, some of the C19MC microRNAs are only downregulated just in preeclampsia.

Influence of parity on fetal hemodynamics and amniotic fluid volume at term

OBJECTIVES

Pregnancy complications, particularly those associated with placental dysfunction, occur more frequently in nulliparous than in parous women. This difference may be a consequence of improved trophoblastic invasion and, as a result, improved placental function following previous pregnancy. Placental dysfunction in cases of fetal growth restriction may be identified by ultrasound assessment of fetoplacental hemodynamics and amniotic fluid volume. In this prospective observational study, we investigated whether differences in these measures of placental function exist between nulliparous and parous women, prior to active labor.

METHODS

Over a 2-year period, 456 nulliparous and 152 parous women with uncomplicated singleton pregnancies were recruited to this prospective observational study. Each participant underwent an ultrasound assessment prior to active labor, during which fetal biometry, umbilical artery, middle cerebral artery and umbilical venous Dopplers, as well as amniotic fluid volume, were assessed. All cases were followed up within 48 h of delivery. Ultrasound parameters and intrapartum outcomes were then compared between the nulliparous and parous groups.

RESULTS

Compared with nulliparous women, parous women had significantly higher fetal middle cerebral artery pulsatility index, cerebroplacental ratio and amniotic fluid volume. In nulliparous women, middle cerebral artery flow rate was also significantly higher and represented a greater percentage of umbilical venous flow than was observed in parous women.

CONCLUSION

Prior to the active phase of labor, ultrasound parameters indicative of placental function differ significantly between nulliparous and parous pregnancy, even amongst an uncomplicated, low-risk cohort.

Risk of intrauterine growth restriction among HIV-infected pregnant women: a cohort study

The purpose of this investigation was to study the risk of intrauterine growth restriction in human immunodeficiency virus (HIV)-infected women and to describe the associated risk factors. A cohort study was performed among HIV-infected women who delivered in a single tertiary centre in Barcelona, Spain, from January 2006 to December 2011. Consecutive singleton pregnancies delivered beyond 22 weeks of pregnancy were included. Intrauterine growth restriction (IUGR) was defined as a birth weight below the 10th customised centile for gestational age and IUGR babies were compared to non-IUGR newborns. Intrauterine Doppler findings were described among IUGR foetuses. Baseline characteristics, HIV infection data and perinatal outcome were compared between groups. The results were adjusted for potential confounders. A total of 156 singleton pregnancies were included. IUGR occurred in 23.4 % of cases (38/156). In two-thirds of the cases detected before birth, Doppler abnormalities compatible with placental insufficiency were observed. IUGR pregnancies presented a worse perinatal outcome, mainly due to a higher risk of iatrogenic preterm delivery [adjusted odds ratio 6.9, 95 % confidence interval (CI) 1.4-33.5]. IUGR foetuses also had a higher risk of emergent Caesarean section and neonatal intensive care unit admission. No cases of intrauterine foetal death occurred. A high rate of IUGR was observed among HIV pregnancies, and it was associated with adverse perinatal outcomes, mainly iatrogenic preterm and very preterm birth due to placental insufficiency. Our results support that ultrasound detection and follow-up of IUGR foetuses should be part of routine antenatal care in this high-risk population to improve antenatal management.

Doppler ultrasound evaluation in preeclampsia

Background

Worldwide preeclampsia (PE) is the leading cause of maternal death and affects 5 to 8% of pregnant women. PE is characterized by elevated blood pressure and proteinuria. Doppler Ultrasound (US) evaluation has been considered a useful method for prediction of PE; however, there is no complete data about the most frequently altered US parameters in the pathology. The aim of this study was to evaluate the uterine, umbilical, and the middle cerebral arteries using Doppler US parameters [resistance index (RI), pulsatility index (PI), notch (N), systolic peak (SP) and their combinations] in pregnant women, in order to make a global evaluation of hemodynamic repercussion caused by the established PE.

Results

A total of 102 pregnant Mexican women (65 PE women and 37 normotensive women) were recruited in a cases and controls study. Blood velocity waveforms from uterine, umbilical, and middle cerebral arteries, in pregnancies from 24 to 37 weeks of gestation were recorded by trans-abdominal examination with a Toshiba Ultrasound Power Vision 6000 SSA-370A, with a 3.5 MHz convex transducer. Abnormal general Doppler US profile showed a positive association with PE [odds ratio (OR) = 2.93, 95% confidence interval (CI) = 1.2 - 7.3, P = 0.021)], and a specificity and predictive positive value of 89.2% and 88.6%, respectively. Other parameters like N presence, RI and PI of umbilical artery, as well as the PI of middle cerebral artery, showed differences between groups (P values < 0.05).

Conclusion

General Doppler US result, as well as N from uterine vessel, RI from umbilical artery, and PI from umbilical and middle cerebral arteries in their individual form, may be considered as tools to determine hemodynamic repercussion caused by PE.

Doppler velocimetry of the fetal middle cerebral artery and other parameters of fetal well-being in neonatal survival during pregnancies with placental insufficiency

OBJECTIVE

To study the Doppler velocimetry of the fetal middle cerebral artery in pregnancies complicated by placental insufficiency, and to verify its role in the prognosis of neonatal survival.

METHODS

This was a prospective study of 93 pregnant women with diagnosis of placental insufficiency detected before the 34(th) week of pregnancy. Placental insufficiency was characterized by abnormal umbilical artery (UA) Doppler (> 95(th) percentile). The following parameters were analyzed: umbilical artery (UA) pulsatility index (PI); middle cerebral artery (MCA) PI; brain-placenta ratio--BPR (MCA-PI/UA-PI); MCA peak systolic velocity (MCA-PSV); and PI for veins (PIV) of ductus venosus (DV). The parameters were analyzed in terms of absolute values, z-scores (standard deviations from the mean), or multiples of the median (MoM). The outcome investigated was neonatal death during the hospitalization period after birth.

RESULTS

Of the 93 pregnancies analyzed, there were 25 (26.9%) neonatal deaths. The group that died, when compared to the survival group, presented a significant association with the diagnosis of absent or reversed end-diastolic flow (88% vs. 23.6%, p<0.001), with a higher median of UA PI (2.9 vs. 1.7, p<0.001) and UA PI z-score (10.4 vs. 4.9, p<0.001); higher MCA-PSV MoM (1.4 vs. 1.1, p=0.012); lower BPR (0.4 vs. 0.7, p<0.001); higher PIV-DV (1.2 vs. 0.8, p<0.001) and DV z-score (3.6 vs. 0.6, p<0.001). In the logistic regression, the independent variables predictive of neonatal death were: gestational age at birth (OR=0.45; 95% CI: 0.3 to 0.7; p<0.001) and UA PI z-score (OR=1.14, 95% CI: 1.0 to 1.3, p=0.046).

CONCLUSION

Despite the association verified by the univariate analysis between neonatal death and the parameters of fetal cerebral Doppler velocimetry, the multivariate analysis identified prematurity and degree of insufficiency of placental circulation as independent factors related to neonatal death in pregnancies complicated by placental insufficiency.

The role of doppler ultrasound in high risk pregnancy: A comparative study

Background:

The objective was to determine the effectiveness of Doppler velocimetry results in the management of high-risk pregnancy.

Materials and Methods:

This cohort study was conducted from January 2005 to December 2006 in Obstetrics and Gynecology Department of Alnoor Specialist Hospital, Makkah, Saudi Arabia. A total of 200 high-risk pregnant women with gestational age >28 weeks were selected for the study and divided into group A (100) subjected to Doppler velocimetry and group B (100) without Doppler velocimetry. Standard management protocols were followed in all cases. The primary outcome measures were mode of delivery and gestational age at the time of delivery. The secondary outcome measures were prenatal and neonatal complications. Data were analyzed using SPSS version 16 (SPSS Inc., Chicago, IL, USA).

Results:

Preterm deliveries, preterm as well as full-term neonatal admissions were more frequent in group A than those in group B, i.e., (39% vs. 26%), (56% vs. 88%) (OR 0.2, 95% CI 0.04-0.7), and (30% vs. 57%) (OR 0.3, 95% CI 0.2-0.7), respectively. Similarly preterm and full-term neonatal deaths were rare in group A than those in group B, i.e., (9% vs. 78%) (OR 0.1, 95% CI 0.02-0.7), and (6% vs. 29%) (OR 0.2, 95% CI 0.03-1.8), respectively. Emergency caesarean section rate was rare in the subjects with normal Doppler than those with abnormal Doppler (48% vs. 100%) (OR 0.1, 95% CI 0.03-0.4) as well as in group B (48% vs. 82%) (OR 0.2, 95% CI 0.1-0.4).

Conclusion:

Doppler studies in high-risk pregnancies are more beneficial in the management of perinatal as well as neonatal management.

Imaging and assessment of placental function

The placenta is the vital support organ for the developing fetus. This article reviews current ultrasound (US) methods of assessing placental function. The ability of ultrasound to detect placental pathology is discussed. Doppler technology to investigate the fetal, placental, and maternal circulations in both high-risk and uncomplicated pregnancies is discussed and the current literature on the value of three-dimensional power Doppler studies to assess placental volume and vascularization is also evaluated. The article highlights the need for further research into three-dimensional ultrasound and alternative methods of placental evaluation if progress is to be made in optimizing placental function assessment.

Normal reference ranges of fetal regional cerebral blood perfusion as measured by fractional moving blood volume

OBJECTIVES

To establish normal reference intervals of fetal regional brain blood perfusion using power Doppler ultrasound as measured by fractional moving blood volume (FMBV).

METHODS

A cohort of consecutive singleton normally grown fetuses was selected including at least 12 fetuses for each completed week of gestation between 24 and 41 weeks. Cerebral blood perfusion was estimated using conventional power Doppler ultrasound in the following brain regions: frontal area, basal ganglia and posterior brain. Five consecutive good-quality images were recorded in each area and the region of interest was delineated offline. The FMBV was quantified as the average of all images and expressed as a percentage. Normal reference ranges were constructed by means of the LMS (lambda-mu-sigma) method.

RESULTS

A total of 230 fetuses were included. The median gestational age at evaluation and at delivery was 33.1 (range, 24.0-41.0) and 39.7 (range, 34.9-42.3) weeks, respectively. From 24 to 41 weeks' gestation, the mean FMBV increased from 13.21 to 14.97% in the frontal area, 11.17 to 14.86% in the basal ganglia and 4.83 to 6.70% in the posterior brain.

CONCLUSIONS

Normal data of fetal cerebral blood perfusion in the frontal area, basal ganglia and posterior brain are provided, which could be of clinical use in the assessment of fetal brain circulation.