Reference ranges for Doppler indices of umbilical and fetal middle cerebral arteries and cerebroplacental ratio: systematic review

Peripartum fetal Doppler sonography and perinatal outcome: a systematic review and meta-analysis

OBJECTIVE

Systematically review and critically appraise the literature on the association between peripartum fetal Doppler sonography findings, i.e., acquired upon admission for spontaneous or induced labor, and perinatal outcome in term (37-42w) pregnancies.

METHODS

Medline, Embase, Web of Science, Cochrane Library, and clinicaltrials.gov databases were systematically searched from inception to 05/2024. Studies conducted in unselected populations of term (37-42w) pregnancies, admitted for spontaneous or induced labor, reporting the association between fetal Doppler findings and perinatal outcome, were eligible for inclusion. Study eligibility was assessed independently by two reviewers. Methodological quality was assessed using the Quality In Prognosis Studies (QUIPS)-tool. Effect estimates were pooled using random-effects meta-analyses. Summary Odds Ratios (ORs) and Mean Differences (MDs) are reported with 95% confidence intervals.

RESULTS

Thirty-seven studies, reporting on 11.505 women and neonates, were included. Fourteen studies reported on findings from the umbilical artery (UA), four on the middle cerebral artery (MCA), five on the umbilical vein (UV), and nine on the cerebroplacental ratio (CPR). An abnormal UA Doppler and CPR increased the odds of fetal distress (FD) during labor (UA: OR 3.67 [1.14, 11.78], I2 = 72% - CPR: OR 3.19 [2.68, 3.80], I2 = 0%) and subsequent operative delivery (ODFD) (UA: OR 3.65 [1.66, 8.04], I2 = 81% - CPR: OR 2.48 [1.66, 3.70], I2 = 57%). Likewise, the presence of UV pulsations was strongly associated with both outcomes (FD: OR 28.78 [11.21, 73.87], I2 = 0% - ODFD: OR 303.36 [11.11, 8279.82], I2 = 0%). Regarding neonatal outcome, an Apgar-score < 7 at 5 min and NICU admission occurred more frequently if Doppler findings were abnormal in the UA (Apgar: OR 3.65 [1.82, 7.34], I2 = 0% - NICU: OR 3.92 [2.36, 6.51], I2 = 0%), or in case of an abnormal CPR (Apgar: OR 3.64 [2.03, 6.54], I2 = 0% - NICU: OR 2.71 [1.15, 6.38], I2 = 0%). Neonatal birthweight was also lower in the presence of an abnormal UA or CPR result, with a MD of -630.61g ([-1234.29, -26.93], I2 = 80%) and -146.52g ([-285.03, -8.01], I2 = 0%) respectively. Most studies (70.3%) were at high risk of bias on one or more domains; only 11 studies had an overall low risk of bias score.

CONCLUSION

Doppler sonography in the peripartum period allows for the identification of fetuses at risk of adverse birth outcomes. Further research on optimal thresholds to define at-risk cases and subsequent management strategies is needed.

PROSPERO REGISTRATION NUMBER

CRD42023413264.

Prediction models for intrapartum fetal hypoxia: A systematic review

BACKGROUND

Intrapartum fetal hypoxia (IFH) occurs infrequently and many cases occur unexpectedly, highlighting the importance of identifying at-risk fetuses to prevent hypoxic injury during birth.

OBJECTIVES

This systematic review aims to evaluate existing prediction models for IFH and ascertain the predictor variables that were incorporated into most models.

SEARCH STRATEGY

We searched MEDLINE and EMBASE databases from inception to December 2023 for synonyms of fetal distress, operative birth and neonatal asphyxia, with a filter for prediction models.

SELECTION CRITERIA

Prediction models for IFH were included. IFH was defined as evidence of hypoxia or operative intervention for suspected fetal distress.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted information on study design, outcome definition and validation. We evaluated study quality using the PROBAST tool. The number of models in which each predictor variable significantly contributed to the risk of IFH was quantified.

MAIN RESULTS

From 874 articles, 23 publications reported on 41 eligible prediction models. 32 models reported on model development only, while seven models across three studies included both development and internal validation. Of these, two models were also externally validated and refit to the validation data, but investigated fetuses with antenatally-suspected growth restriction, limiting generalisability. Frequently reported predictor variables included parity (13 studies), cerebroplacental ratio (10 studies) and oxytocin use (6 studies).

CONCLUSIONS

No prediction models for IFH applicable to the general population are currently ready for clinical application. External validation of existing models or development of new, reliable models applicable to all pregnant women is needed.

Fetal Doppler assessment in pregnancy

Fetal Doppler assessment plays a crucial role in monitoring the fetal well-being during pregnancy. This non-invasive technique assesses blood flow dynamics in key fetal vessels, namely the umbilical artery, middle cerebral artery, and ductus venosus. The umbilical artery Doppler provides valuable insights into placental function aiding in the early detection of fetal growth restriction and fetal distress. Assessment of the middle cerebral artery Doppler provides information on the adequacy of cerebral perfusion. It is highly sensitive to changes in fetal oxygenation and contributes to the management of advanced stages of early fetal growth restriction. It is also a valuable and sometimes standalone marker for late-term fetal hypoxic compromise and fetal anemia. Doppler evaluation of ductus venosus offers additional data for identifying cardiac compromise and predicting adverse perinatal outcomes. Incorporating these Doppler assessments into routine prenatal care enhances the ability to detect and manage fetal compromise, ultimately improving pregnancy outcomes.

Methodology Used in Studies Aimed at Measuring Fetal Soft Tissues by 2D Ultrasound for the Screening of Large for Gestational Age Fetuses: A Systematic Review

Management of suspected large for gestational age (LGA) fetuses remains unclear because ultrasound-estimated fetal weight (EFW) is not accurate. This was a systematic review of observational studies on fetal soft tissues measurements used alone or in combination to create a new EFW formula, to improve the screening for LGA fetuses. Studies were scored using a predefined set of independently agreed methodological criteria and an overall quality score was assigned for study design, statistical analysis, and reporting methods. There is a need to standardize methodologies for soft fetal tissue measurements. We propose a set of suggestions for this purpose.

Reproducibility of fetal ultrasound doppler parameters used for growth assessment

OBJECTIVES

To produce standards of references for quality control and assess the reproducibility of fetal ultrasound Doppler measurements commonly used for blood flow assessment in fetal growth.

METHODS

Women with singleton normal pregnancies were prospectively recruited at University College London Hospital, UK, between 24 and 41 weeks. Umbilical artery (UA), middle cerebral artery (MCA), and their pulsatility indices (PI), resistance indices (RI) and ratios such as cerebro-placental (CPR) and umbilical cerebral ratio (UCR) were obtained twice by two sonographers in training or after completion of training, blind to each other's measurements. Bland-Altman plots were generated, the mean differences and 95% limits of agreement (LOA) were calculated to assess intra- and interobserver reproducibility. Values were expressed as absolute values or as z-score.

RESULTS

One hundred ten women were recruited. Overall reproducibility was variable for absolute values and highly variable for z-scores, independently from vessel sampled, index or ratio used, intra- or interobserver reproducibility. The widest absolute values of 95% LOA were 0.3 for UA PI, 0.7 for MCA PI, 0.9 for CPR and 0.3 for UCR, respectively. Regarding z-score, the widest 95% LOA were 1.9 for UA PI, 2.1 for CPR and 1 for UCR. Reproducibility was slightly better for intra- compared with interobserver variability. There was significant difference in z-score reproducibility between MCA peak systolic velocity and CPR vs UCR.

CONCLUSIONS

Reference standards of reproducibility of fetal Doppler parameters are produced for standardization and quality-control purposes. Overall, the reproducibility for fetal Doppler parameters was variable independently from vessel sampled, Doppler index (PI or RI) or ratio used, intra- and interobserver comparison. UCR was the most reproducible parameter which should be recommended, together with UA PI, for clinical use and in research studies on fetal growth.

Comparison of umbilical artery pulsatility index reference ranges

OBJECTIVE

To compare the accuracy of four published reference standards for the umbilical artery pulsatility index (UA-PI) in predicting small-for-gestational age (SGA), adverse neonatal outcomes and obstetric complications in pregnancies at risk for fetal growth restriction.

METHODS

This was a secondary analysis of a prospective study of singleton pregnancies that underwent fetal growth assessment by ultrasound between 26 and 36 weeks' gestation. Pregnancies with estimated fetal weight or abdominal circumference < 20th percentile with UA-PI measurements available were included. We excluded fetuses with chromosomal anomaly or congenital malformation and those without delivery information. The predictive ability of UA-PI > 95th percentile according to the reference standards of Acharya et al., the INTERGROWTH-21st Project, the Fetal Medicine Foundation and Parra-Cordero et al. for SGA, a composite of adverse neonatal outcomes and a composite of obstetric complications was compared using the area under the receiver-operating-characteristics curve (AUC). Sensitivity, specificity and positive and negative predictive values were calculated.

RESULTS

Of the 1054 pregnancies that underwent fetal growth evaluation by ultrasound, 207 were included in our analysis. SGA, adverse neonatal outcomes and obstetric complications were diagnosed in 94 (45.4%), 50 (24.2%) and 69 (33.3%) cases, respectively. All reference standards had similar and statistically significant but poor predictive accuracy for SGA (AUC of 0.55 to 0.56), adverse neonatal outcomes (AUC of 0.57 to 0.60) and obstetric complications (AUC of 0.55 for all).

CONCLUSIONS

The reference standards for UA-PI evaluated herein have poor predictive ability for SGA, adverse neonatal outcomes and obstetric complications. At present, no particular UA-PI reference standard can be recommended over others. Larger trials are needed to answer this research question. © 2024 International Society of Ultrasound in Obstetrics and Gynecology.

Ultrasound visualization and blood flow velocity measurements of the adrenal arteries in the fetus

INTRODUCTION

Detection and surveillance of fetal growth restriction (FGR) is well established, but there is still room for improvement. Animal studies indicate that compromised fetuses increase adrenal blood flow. Modern ultrasound equipment allows us to measure vascular impedance in the fetal adrenal arteries despite their modest size. However, extensive anatomical variance is a challenge to standardizing measurements. We set out to improve this.

MATERIAL AND METHODS

We included 75 low-risk pregnant women in a prospective cross-sectional study aiming to develop a reliable technique to visualize and measure flow velocity in human fetal adrenal arteries. We used commercially available ultrasound equipment: a GE Voluson 10 2019 with a C2-9 probe (GE Healthcare, Zipf, Austria), and a Philips Epiq Elite with a V9-2 probe (Philips Medical Systems International B.V., Best, The Netherlands), exploiting the modern sensitive power Doppler modes in both scanners to visualize small vessels.

RESULTS

Among 72 fetuses, the inferior adrenal artery was the most consistently visualized and measured artery to the gland. Doppler velocimetry was achieved in 66 (92%) participants. We found the anatomical variation described previously but were able to develop visualization strategies to identify the common arteries and use a consistent Doppler technique for the second half of pregnancy.

CONCLUSIONS

It is possible to visualize and measure flow velocity in the adrenal arteries of human fetuses. The success rate was highest for the inferior adrenal artery making this vessel a candidate for clinical studies.

Prenatal exposure to per- and polyfluoroalkyl substances, fetoplacental hemodynamics, and fetal growth

INTRODUCTION

The impact of legacy per- and polyfluoroalkyl substances (PFAS) on fetal growth has been well studied, but assessments of next-generation PFAS and PFAS mixtures are sparse and the potential role of fetoplacental hemodynamics has not been studied. We aimed to evaluate associations between prenatal PFAS exposure and fetal growth and fetoplacental hemodynamics.

METHODS

We included 747 pregnant women from the BiSC birth cohort (Barcelona, Spain (2018-2021)). Twenty-three PFAS were measured at 32 weeks of pregnancy in maternal plasma, of which 13 were present above detectable levels. Fetal growth was measured by ultrasound, as estimated fetal weight at 32 and 37 weeks of gestation, and weight at birth. Doppler ultrasound measurements for uterine (UtA), umbilical (UmA), and middle cerebral artery (MCA) pulsatility indices (PI), as well as the cerebroplacental ratio (CPR - ratio MCA to UmA), were obtained at 32 weeks to assess fetoplacental hemodynamics. We applied linear mixed effects models to assess the association between singular PFAS and longitudinal fetal growth and PI, and Bayesian Weighted Quantile Sum models to evaluate associations between the PFAS mixture and the aforementioned outcomes, controlled for the relevant covariates.

RESULTS

Single PFAS and the mixture tended to be associated with reduced fetal growth and CPR PI, but few associations reached statistical significance. Legacy PFAS PFOS, PFHpA, and PFDoDa were associated with statistically significant decreases in fetal weight z-score of 0.13 (95%CI (-0.22, -0.04), 0.06 (-0.10, 0.01), and 0.05 (-0.10, 0.00), respectively, per doubling of concentration. The PFAS mixture was associated with a non-statistically significant 0.09 decrease in birth weight z-score (95%CI -0.22, 0.04) per quartile increase.

CONCLUSION

This study suggests that legacy PFAS may be associated with reduced fetal growth, but associations for next generation PFAS and for the PFAS mixture were less conclusive. Associations between PFAS and fetoplacental hemodynamics warrant further investigation.

Reply to Rubin, J.M.; Kripfgans, O.D. Comment on "Barbieri et al. Umbilical Vein Blood Flow in Uncomplicated Pregnancies: Systematic Review of Available Reference Charts and Comparison with a New Cohort. J. Clin. Med. 2023, 12, 3132"

We thank the authors for the interest in our paper [...].

Assessing the external validity and clinical relevance of umbilical doppler resistance index references in daily practice

OBJECTIVE

To assess the external validity and clinical relevance of current references for umbilical artery resistance index (UA RI) in daily practice.

METHODS

Retrospective cross-sectional single center study including all UA RI measurements between 22 and 40 gestational weeks (GW) from distinct patients between 2014 and 2022. Patients with normal pregnancies and normal neonatal outcomes that had an UA RI measurement between 2014 and 2019 were used to calculate reference ranges. The established reference for the 95th centile was compared to two current references. The clinical relevance of the established reference was tested by comparing neonatal outcomes according to the 95th percentile among the consecutive distinct patients between 2020 and 2022.

RESULTS

Among the 13342 consecutive distinct patients with a singleton pregnancy that had an UA RI measurement between 22 and 40 GW between 2014 and 2022, 5298 patients were included to establish the reference ranges, and 3634 patients to validate these ranges. For each gestational age, the established references were similar to current references. Using the established references, the proportion of patients presenting an UA RI>95th percentile among the patients with normal pregnancies in the validation population was comparable to the proportion when using the two current references. Among the validation population, 268 patients (7.4 %) (95%CI[6.5-8.2]) presented an UA RI ≥ 95th percentile. Of these 268 patients, 67.9% had a SGA newborn (versus 19.2%, p<0.001) and 59% a preterm birth (versus 13.9%, p<0.001).

CONCLUSIONS

The reference range obtained from daily practice is clinically relevant and similar to current references.

Do differences in diagnostic criteria for late fetal growth restriction matter?

BACKGROUND

Criteria for diagnosis of fetal growth restriction differ widely according to national and international guidelines, and further heterogeneity arises from the use of different biometric and Doppler reference charts, making the diagnosis of fetal growth restriction highly variable.

OBJECTIVE

This study aimed to compare fetal growth restriction definitions between Delphi consensus and Society for Maternal-Fetal Medicine definitions, using different standards/charts for fetal biometry and different reference ranges for Doppler velocimetry parameters.

STUDY DESIGN

From the TRUFFLE 2 feasibility study (856 women with singleton pregnancy at 32+0 to 36+6 weeks of gestation and at risk of fetal growth restriction), we selected 564 women with available mid-pregnancy biometry. For the comparison, we used standards/charts for estimated fetal weight and abdominal circumference from Hadlock, INTERGROWTH-21st, and GROW and Chitty. Percentiles for umbilical artery pulsatility index and its ratios with middle cerebral artery pulsatility index were calculated using Arduini and Ebbing reference charts. Sensitivity and specificity for low birthweight and adverse perinatal outcome were evaluated.

RESULTS

Different combinations of definitions and reference charts identified substantially different proportions of fetuses within our population as having fetal growth restriction, varying from 38% (with Delphi consensus definition, INTERGROWTH-21st biometric standards, and Arduini Doppler reference ranges) to 93% (with Society for Maternal-Fetal Medicine definition and Hadlock biometric standards). None of the different combinations tested appeared effective, with relative risk for birthweight <10th percentile between 1.4 and 2.1. Birthweight <10th percentile was observed most frequently when selection was made with the GROW/Chitty charts, slightly less with the Hadlock standard, and least frequently with the INTERGROWTH-21st standard. Using the Ebbing Doppler reference ranges resulted in a far higher proportion identified as having fetal growth restriction compared with the Arduini Doppler reference ranges, whereas Delphi consensus definition with Ebbing Doppler reference ranges produced similar results to those of the Society for Maternal-Fetal Medicine definition. Application of Delphi consensus definition with Arduini Doppler reference ranges was significantly associated with adverse perinatal outcome, with any biometric standards/charts. The Society for Maternal-Fetal Medicine definition could not accurately detect adverse perinatal outcome irrespective of estimated fetal weight standard/chart used.

CONCLUSION

Different combinations of fetal growth restriction definitions, biometry standards/charts, and Doppler reference ranges identify different proportions of fetuses with fetal growth restriction. The difference in adverse perinatal outcome may be modest, but can have a significant impact in terms of rate of intervention.

Highlighting early detection of thyroid pathology and gestational diabetes effects on oxidative stress that provokes preterm delivery in thyroidology: Does that ring a bell?

OBJECTIVES

Ad fontes, the status of the thyroid gland, and metabolic disturbance lead to the alteration of oxygenation. In pregnancy, it is particularly crucial to possess all predictive parameters.

METHODS

This cross-sectional study was conducted at the Clinic of Gynecology and Obstetrics, Clinical Center of Serbia, Belgrade, Serbia, between 2017 and 2021 which study included a total of 99 women who had been admitted for preterm delivery and had undergone thyroid analysis, detected Hashimoto thyroiditis, and Oral Glucose Tolerance Test (OGTT) 40 days after delivery and had pathological Homeostatic Model Assessment for Insulin Response (HOMA IR) indices. In the group of urgent patients with preterm delivery, we looked after not only routine Doppler of the umbilical artery, but we measured specific ratios such as the Cerebroplacental ratio (CP).

RESULTS

The mean maternal age was 32.23 ± 5.96 years and the mean gestational age was detected as 35.40 ± 2.39 weeks. The delivery was completed vaginally in 77 women (78%) and surgically in 22 (22%). The Mean APGAR score was 8.44 ± 1.18, the mean birth weight was 2666.87 ± 622.17g and the cases undergoing cesarean section had significantly higher values of pulsatility index (1.85 ± 0.27 vs. 1.34 ± 0.31) and CP (1.22 ± 0.26 vs. 0.47 ± 0.17).

CONCLUSIONS

The introduction of Doppler sonography for blood flow assessment helps to form a complete clinical description of the patient, particularly in conditions where oxidative stress became provocative by the thyroid gland antibodies and gestational diabetes in Thyroidology.

Maternal PlGF and umbilical Dopplers predict pregnancy outcomes at diagnosis of early-onset fetal growth restriction

BACKGROUNDSevere, early-onset fetal growth restriction (FGR) causes significant fetal and neonatal mortality and morbidity. Predicting the outcome of affected pregnancies at the time of diagnosis is difficult, thus preventing accurate patient counseling. We investigated the use of maternal serum protein and ultrasound measurements at diagnosis to predict fetal or neonatal death and 3 secondary outcomes: fetal death or delivery at or before 28+0 weeks, development of abnormal umbilical artery (UmA) Doppler velocimetry, and slow fetal growth.METHODSWomen with singleton pregnancies (n = 142, estimated fetal weights [EFWs] below the third centile, less than 600 g, 20+0 to 26+6 weeks of gestation, no known chromosomal, genetic, or major structural abnormalities) were recruited from 4 European centers. Maternal serum from the discovery set (n = 63) was analyzed for 7 proteins linked to angiogenesis, 90 additional proteins associated with cardiovascular disease, and 5 proteins identified through pooled liquid chromatography and tandem mass spectrometry. Patient and clinician stakeholder priorities were used to select models tested in the validation set (n = 60), with final models calculated from combined data.RESULTSThe most discriminative model for fetal or neonatal death included the EFW z score (Hadlock 3 formula/Marsal chart), gestational age, and UmA Doppler category (AUC, 0.91; 95% CI, 0.86-0.97) but was less well calibrated than the model containing only the EFW z score (Hadlock 3/Marsal). The most discriminative model for fetal death or delivery at or before 28+0 weeks included maternal serum placental growth factor (PlGF) concentration and UmA Doppler category (AUC, 0.89; 95% CI, 0.83-0.94).CONCLUSIONUltrasound measurements and maternal serum PlGF concentration at diagnosis of severe, early-onset FGR predicted pregnancy outcomes of importance to patients and clinicians.TRIAL REGISTRATIONClinicalTrials.gov NCT02097667.FUNDINGThe European Union, Rosetrees Trust, Mitchell Charitable Trust.

Doppler Indices of the Uterine, Umbilical and Fetal Middle Cerebral Artery in Diabetic versus Non-Diabetic Pregnancy: Systematic Review and Meta-Analysis

Background and Objectives: The aim of this study was to assess the differences in Doppler indices of the uterine (Ut), umbilical (UA), and middle cerebral artery (MCA) in diabetic versus non-diabetic pregnancies by conducting a comprehensive systematic review of the literature with a meta-analysis. Materials and Methods: PubMed, Web of Science, and SCOPUS were searched for studies that measured the pulsatility index (PI), resistance index (RI), and systolic/diastolic ratio index (S/D ratio) of the umbilical artery, middle cerebral artery, and uterine artery in diabetic versus non-diabetic pregnancies. Two reviewers independently evaluated the eligibility of studies, abstracted data, and performed quality assessments according to standardized protocols. The standardized mean difference (SMD) was used as a measure of effect size. Heterogeneity was assessed using the I2 statistic. Publication bias was evaluated by means of funnel plots. Results: A total of 62 publications were included in the qualitative and 43 in quantitative analysis. The UA-RI, UtA-PI, and UtA-S/D ratios were increased in diabetic compared with non-diabetic pregnancies. Subgroup analysis showed that levels of UtA-PI were significantly higher during the third, but not during the first trimester of pregnancy in diabetic versus non-diabetic pregnancies. No differences were found for the UA-PI, UA-S/D ratio, MCA-PI, MCA-RI, MCA-S/D ratio, or UtA-RI between diabetic and non-diabetic pregnancies. Conclusions: This meta-analysis revealed the presence of hemodynamic changes in uterine and umbilical arteries, but not in the middle cerebral artery in pregnancies complicated by diabetes.

Advanced imaging of fetal cardiac function

Over recent decades, a variety of advanced imaging techniques for assessing cardiovascular physiology and cardiac function in adults and children have been applied in the fetus. In many cases, technical development has been required to allow feasibility in the fetus, while an appreciation of the unique physiology of the fetal circulation is required for proper interpretation of the findings. This review will focus on recent advances in fetal echocardiography and cardiovascular magnetic resonance (CMR), providing examples of their application in research and clinical settings. We will also consider future directions for these technologies, including their ongoing technical development and potential clinical value.

Developmental Ultrasound Characteristics in Guinea Pigs: Similarities with Human Pregnancy

BACKGROUND

Biometrical and blood flow examinations are fundamental for assessing fetoplacental development during pregnancy. Guinea pigs have been proposed as a good model to study fetal development and related gestational complications; however, longitudinal growth and blood flow changes in utero have not been properly described. This study aimed to describe fetal and placental growth and blood flow of the main intrauterine vascular beds across normal guinea pig pregnancy and to discuss the relevance of this data for human pregnancy.

METHODS

Pregnant guinea pigs were studied from day 25 of pregnancy until term (day ~70) by ultrasound and Doppler assessment. The results were compared to human data from the literature.

RESULTS

Measurements of biparietal diameter (BPD), cranial circumference (CC), abdominal circumference, and placental biometry, as well as pulsatility index determination of umbilical artery, middle cerebral artery (MCA), and cerebroplacental ratio (CPR), were feasible to determine across pregnancy, and they could be adjusted to linear or nonlinear functions. In addition, several of these parameters showed a high correlation coefficient and could be used to assess gestational age in guinea pigs. We further compared these data to ultrasound variables from human pregnancy with high similarities.

CONCLUSIONS

BPD and CC are the most reliable measurements to assess fetal growth in guinea pigs. Furthermore, this is the first report in which the MCA pulsatility index and CPR are described across guinea pig gestation. The guinea pig is a valuable model to assess fetal growth and blood flow distribution, variables that are comparable with human pregnancy.

Reference Ranges for Vermis Biometry on Prenatal Ultrasound: Systematic Review and Meta-Analysis

PURPOSE

 To conduct a systematic review and meta-analysis of published nomograms for fetal vermis biometry.

MATERIALS AND METHODS

 A structured literature search was conducted to identify studies that reported normal measurements of the fetal vermis. A customized quality assessment tool was used to review the selected articles. Random effects meta-analysis was used to calculate normal ranges for vermian craniocaudal diameter, anteroposterior diameter, and surface area.

RESULTS

 A total of 21 studies were included for qualitative review and 3 studies were included for quantitative synthesis. The 3 included articles comprised a total of 10 910 measurements from gestational ages 17-35 weeks. The quality assessment demonstrated that there was generally poor reporting regarding maternal characteristics and neonatal outcomes. Except for one article with a large sample size, the mean number of fetuses per week of gestational age was 15.9, with the lowest number being 5. There was significant statistical heterogeneity. Non-visualization rates ranged from 0-35.4 %. The craniocaudal diameter (reported in 3 articles) increased from a mean of 7.90 mm (95 % confidence interval [CI] 7.42, 8.38) at 17 weeks to 21.90 mm (95 % CI 20.63, 23.16) at 35 weeks gestation. The anteroposterior diameter (reported in 2 articles) increased from 6.30 mm (95 % CI 5.42, 7.18) at 17 weeks to 15.85 (95 %CI 15.49, 16.21) at 32 weeks.

CONCLUSION

 Reference ranges for vermis biometry across gestation based on meta-analysis of existing references are provided. However, because many of the underlying studies suffered from significant methodological issues, the ranges should be used with caution.

Early Onset Intrauterine Growth Restriction-Data from a Tertiary Care Center in a Middle-Income Country

Background and Objectives: In this study, we aimed to describe the clinical and ultrasound (US) features and the outcome in a group of patients suspected of or diagnosed with early onset intrauterine growth restriction (IUGR) requiring iatrogenic delivery before 32 weeks, having no structural or genetic fetal anomalies, managed in our unit. A secondary aim was to report the incidence of the condition in the population cared for in our hospital, data on immediate postnatal follow-up in these cases and to highlight the differences required in prenatal and postnatal care. Materials and Methods: We used as single criteria for defining the suspicion of early IUGR the sonographic estimation of fetal weight < p10 using the Hadlock 4 technique at any scan performed before 32 weeks’ gestation (WG). We used a cohort of patients having a normal evolution in pregnancy and uneventful vaginal births as controls. Data on pregnancy ultrasound, characteristics and neonatal outcomes were collected and analyzed. We hypothesized that the gestational age (GA) at delivery is related to the severity of the condition. Therefore, we performed a subanalysis in two subgroups, which were divided based on the GA at iatrogenic delivery (between 27+0 WG and 29+6 WG and 30+0−32+0 WG, respectively). Results: The prospective cohort study included 36 pregnancies. We had three cases of intrauterine fetal death (8.3%). The incidence was 1.98% in our population. We confirmed that severe cases (very early diagnosed and delivered) were associated with a higher number of prenatal visits and higher uterine arteries (UtA) pulsatility index (PI) centile in the third trimester—TT (compared with the early diagnosed and delivered). In the very early suspected IUGR subgroup, the newborns required significantly more NICU days and total hospitalization days. Conclusions: Patients with isolated very early and early IUGR—defined as ultrasound (US) estimation of fetal weight < p10 using the Hadlock 4 technique requiring iatrogenic delivery before 32 weeks’ gestation—require closer care prenatally and postnatally. These patients represent an economical burden for the health system, needing significantly longer hospitalization intervals, GA at birth and UtA PI centiles being related to it.

Modeling gestational age centiles for fetal umbilicocerebral ratio by quantile regression analysis: a secondary analysis of a prospective cross-sectional study

OBJECTIVE

There is a lack of evidence on whether to favor cerebroplacental ratio (CPR) or umbilicocerebral ratio (UCR) when assessing pregnancies at risk of fetal growth restriction. The Recent evidences highlight a significant heterogeneity in the methodology of previously published studies reporting reference ranges for Doppler indices, which may affect the clinical applicability of these charts. The aim of this study was to develop charts of UCR based upon a recently proposed standardized methodology and using quantile regression.

METHODS

This was a secondary analysis of a prospective cross-sectional study including low-risk singleton pregnancies between 24 and 40 weeks of gestation undergoing Doppler recordings. The UCR centile values were established by quantile regression at different gestational age intervals. Quantile regression analysis was used to build the UCR chart.

RESULT

2516 low- risk singleton pregnancies were included in the analysis. UCR decreased with advancing gestational age. The 3rd, 5th 10th, 50th, 90th, 95th, and 97th centiles according to gestational age are provided, as well as equations to allow calculation of any other percentile.

CONCLUSIONS

We have established gestational age-specific normative centiles reference limits for UCR.

Reference Ranges for Corpus Callosum and Cavum Septi Pellucidi Biometry on Prenatal Ultrasound: Systematic Review and Meta-Analysis

We conducted a systematic review and meta-analysis of published nomograms for fetal corpus callosum and cavum septi pellucid biometry. A structured literature search was conducted to identify studies that reported normal measurements of the fetal corpus callosum and cavum septi pellucidi. Random effects metaanalysis was used to calculate normal ranges, and reference curves are provided. The quality assessment demonstrated that there was generally poor reporting regarding maternal characteristics and neonatal outcomes. Our findings emphasize that standardization of research protocols and publishing criteria for normal biometric ranges is needed.

Evaluation of the selected parameters of the fetal diastolic functions in normally grown or macrosomic fetuses of gestational diabetic mothers with poor glycaemic control

OBJECTIVE

This study aimed to investigate whether the third trimester fetal cardiac diastolic function measured by selected conventional Doppler indices is affected in appropriate-for-gestational-age or macrosomic fetuses of gestational diabetic mothers with poor glycaemic control.

METHODS

This cross-sectional study included 93 pregnant women divided into two groups. Group 1 included 45 appropriate-for-gestational-age or macrosomic fetuses from gestational diabetic mothers with poor glycaemic control (study group). Group 2 included 48 appropriate-for-gestational-age fetuses from gestational age-matched healthy mothers (control group). Functional fetal cardiac parameters and fetoplacental Doppler parameters were measured. Data were compared between the two groups.

RESULTS

Maternal characteristics did not differ significantly between the study and the control group. There were no significant differences in the early and late velocity, early/late velocity ratio of both mitral and tricuspid valves, the fetal pulmonary vein pulsatility index, and the ductus venosus pulsatility index between the study and the control group. Moreover, the rate of abnormal Doppler findings in pulmonary vein (pulmonary vein pulsatility index >95th centile), ductus venosus (ductus venosus pulsatility index >95th centile), and peripheral vessels (umbilical artery pulsatility index >95th centile, middle cerebral artery pulsatility index <5th centile, cerebra-placental index >95th centile) were comparable in both groups.

CONCLUSIONS

The third trimester fetal diastolic functions measured by selected conventional Doppler techniques do not seem to be altered in appropriate-for-gestational-age or macrosomic fetuses of gestational diabetic mothers who have poor glycaemic control.

Cerebro-placental and umbilico-cerebral ratios in uncomplicated monochorionic twins: Longitudinal references and comparison with singletons

OBJECTIVES

Monochorionic twins (MC) are at high risk of adverse outcomes and Doppler investigation of umbilical and cerebral flows is mandatory for their surveillance. The cerebro-placental (CPR) and umbilico-cerebral (UCR) ratios are considered non-invasive measures of fetal adaptation to hypoxemia. We aimed to provide longitudinal references for CPR and UCR from 16 to 37 weeks of gestation that are specific for MC twins, and compare these with singleton charts.

METHODS

Longitudinal study of a cohort of consecutive uncomplicated MC twin pregnancies monitored at our unit from 2010 to 2018. The estimated centile curves were obtained estimating the median with fractional polynomials by a multilevel model and the external centiles through the residuals. The comparison with singletons references was made through graphic evaluation.

RESULTS

One-hundred-fifty-two MC pregnancies were included with a median of 10 longitudinal ultrasounds each. References for CPR and UCR in function of gestational age are presented. Compared to singletons, MC twins showed an earlier and greater circulatory redistribution with lower CPR and higher UCR median values.

CONCLUSIONS

MC twin-specific references for CPR and UCR suitable for serial monitoring are presented. The comparison with singleton references demonstrates substantial differences in the hemodynamic balance that must be considered when interpreting findings in MC twins. This article is protected by copyright. All rights reserved.

Expected-value bias in mid-trimester preterm birth screening

OBJECTIVES

Cervical length (CL) measurement ≤ 25 mm on mid-trimester ultrasound scan is a known risk factor for preterm birth, for which vaginal progesterone is recommended. The aims of this study were to evaluate whether CL measurement is affected by observer bias and to assess the impact on short cervix prevalence of masking CL measurement during routine mid-trimester ultrasound scan.

METHODS

This was a flash study designed for a 2-month period (October and November 2018) at Cruces University Hospital (Bizkaia, Spain), in which all CL measurements from routine mid-trimester scans were masked. During the study period, there was no modification of the routine screening method, and women with a short cervix were prescribed 200 mg vaginal progesterone daily as per usual. The control group included women examined in a 2-month period (April and May 2018) prior to the study, in which CL measurements were taken as usual by a non-blinded operator. The primary outcome was the prevalence of short cervix in each group.

RESULTS

A total of 983 CL measurements were analyzed, including 457 in the blinded group and 526 in the control group. The prevalence of short cervix was 2.7% in the non-blinded group and 5.5% in the blinded group (P = 0.024). We identified a statistically significant difference in the incidence of CL of 24-25 mm between the two groups, with a lower prevalence in the non-blinded vs blinded group (0.6% vs 2.4%; P < 0.005). Moreover, the distribution of CL values was normal in the blinded group, in contrast to the non-blinded group, which was characterized by skewed distribution of CL values.

CONCLUSIONS

Expected-value bias exists and should be taken into account when measuring CL in mid-trimester preterm birth screening. Blinding has demonstrated to be an effective strategy to improve the performance of CL screening in clinical practice. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Modeling Pulsatility Index nomograms from different maternal and fetal vessels by quantile regression at 24-40 weeks of gestation: a prospective cross-sectional study

OBJECTIVE

Recent evidences highlight a considerable heterogeneity in the methodology of previously published studies reporting reference ranges for maternal and fetal Dopplers, which may have relevant implications in clinical practice. In view of these limitations, a standardized methodology to construct Doppler charts has been proposed. The aim of this study was to develop charts for pulsatility index (PI) of maternal and fetal Dopplers based upon the recently proposed standardized methodology and using quantile regression.

METHODS

Prospective cross-sectional study including 2516 low-risk singleton pregnancies between 24 and 40 weeks of gestation. The mean uterine, umbilical (UA), middle cerebral (MCA) and their ratio (cerebroplacental ratio, CPR) centile values were established by quantile regression in the considered gestational interval. Interclass correlation coefficient (ICC) of each maternal and fetal vessel was also computed to assess the intra- and inter-observer agreement of the results.

RESULTS

There was a good intra- and inter-observer agreement for each of the explored vessels (ICC >0.92 and >0.91 for a single and two observers, respectively). The 5th, 10th, 50th, 90th and 95th centiles of the reference range for gestation were constructed by quantile regression and compared to previously established reference charts. All the Doppler indices significantly changed with gestation. Second-degree polynomial regression models better described the changes with gestation in PCR and MCA PI values while a linear model better predicted the changes of other Doppler indices with advancing gestation. When compared to other studies reporting reference ranges for maternal and fetal Dopplers, the present charts showed similar median values but different distribution from the median.

CONCLUSIONS

We provided prospective charts of maternal and fetal Dopplers based upon a previously proposed standardized methodology and using quantile regression. When compared to previously published studies, these new charts showed similar median values but different deviations from the median which may help in better differentiating cases at higher risk of placental insufficiency and adverse perinatal outcome.

Methodological Quality of Fetal Brain Structure Charts for Screening Examination and Targeted Neurosonography: A Systematic Review

INTRODUCTION

Several fetal brain charts have been published in the literature and are commonly used in the daily clinical practice. However, the methodological quality of these charts has not been critically appraised.

MATERIAL AND METHODS

MEDLINE, EMBASE, CINAHL, and the Web of Science databases were searched electronically up to December 31, 2020. The primary outcome was to evaluate the methodology of the studies assessing the growth of fetal brain structures throughout gestation. A list of 28 methodological quality criteria divided into three domains according to "study design," "statistical and reporting methods," and "specific relevant neurosonography aspects" was developed in order to assess the methodological appropriateness of the included studies. The overall quality score was defined as the sum of low risk of bias marks, with the range of possible scores being 0-28. This quality assessment was applied to each individual study reporting reference ranges for fetal brain structures. Furthermore, we performed a subgroup analysis according to the different brain structures (ventricular and periventricular, fore-brain and midbrain cerebral and posterior fossa).

RESULTS

Sixty studies were included in the systematic review. The overall mean quality score of the studies included in this review was 51.3%. When focusing on each of the assessed domains, the mean quality score was 53.7% for "study design," 54.2% for "statistical and reporting methods," and 38.6% for "specific relevant neurosonography aspects." The sample size calculation, the correlation with a postnatal imaging evaluation, and the whole fetal brain assessment were the items at the highest risk of bias for each domain assessed, respectively. The subgroup analysis according to different anatomical location showed the lowest quality score for ventricular and periventricular structures and the highest for cortical structures.

CONCLUSIONS

Most previously published studies reporting fetal brain charts suffer from poor methodology and are at high risk of biases, mostly when focusing on neurosonography issues. Further prospective longitudinal studies aiming at constructing specific growth charts for fetal brain structures should follow rigorous methodology to minimize the risk of biases, guarantee higher levels of reproducibility, and improve the standard of care.

Doppler Ultrasound of the Umbilical Artery: Clinical Application

OBJECTIVE

 To provide a survey of relevant literature on umbilical artery Doppler ultrasound use in clinical practice, technical considerations and limitations, and future perspectives.

METHODS

 Literature searches were conducted in PubMed and Medline, restricted to articles written in English. Additionally, the references of all analyzed studies were searched to obtain necessary information.

RESULTS

 The use of this technique as a routine surveillance method is only recommended for high-risk pregnancies with impaired placentation. Meta-analyses of randomized trials have established that obstetric management guided by umbilical artery Doppler findings can improve perinatal mortality and morbidity. The values of the indices of Umbilical artery Doppler decrease with advancing gestational age; however, a lack of consensus on reference ranges prevails.

CONCLUSION

 Important clinical decisions are based on the information obtained with umbilical artery Doppler ultrasound. Future efforts in research are imperative to overcome the current limitations of the technique.

Reference ranges for fetal brain structures using magnetic resonance imaging: systematic review

OBJECTIVE

To evaluate the methodology of studies reporting reference ranges for fetal brain structures on magnetic resonance imaging (MRI).

METHODS

MEDLINE, EMBASE, CINAHL and the Web of Science databases were searched electronically up to 31 December 2020 to identify studies investigating biometry and growth of the fetal brain and reporting reference ranges for brain structures using MRI. The primary aim was to evaluate the methodology of these studies. A list of 26 quality criteria divided into three domains, including 'study design', 'statistical and reporting methods' and 'specific aspects relevant to MRI', was developed and applied to evaluate the methodological appropriateness of each of the included studies. The overall quality score of a study, ranging between 0 and 26, was defined as the sum of scores awarded for each quality criterion and expressed as a percentage (the lower the percentage, the higher the risk of bias).

RESULTS

Fifteen studies were included in this systematic review. The overall mean quality score of the studies evaluated was 48.7%. When focusing on each domain, the mean quality score was 42.0% for 'study design', 59.4% for 'statistical and reporting methods' and 33.3% for 'specific aspects relevant to MRI'. For the 'study design' domain, sample size calculation and consecutive enrolment of women were the items found to be at the highest risk of bias. For the 'statistical and reporting methods' domain, the presence of regression equations for mean and SD for each measurement, the number of measurements taken for each variable and the presence of postnatal assessment information were the items found to be at the highest risk of bias. For the 'specific aspects relevant to MRI' domain, whole fetal brain assessment was not performed in any of the included studies and was therefore considered to be the item at the highest risk of bias.

CONCLUSIONS

Most of the previously published studies reporting fetal brain reference ranges on MRI are highly heterogeneous and have low-to-moderate quality in terms of methodology, which is similar to the findings reported for ultrasound studies. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Middle cerebral arterial flow redistribution is an indicator for intrauterine fetal compromise in late pregnancy in low-resource settings: A prospective cohort study

Objective

We aimed to determine the prevalence of abnormal umbilical artery (UA), uterine artery (UtA), middle cerebral artery (MCA) and cerebroplacental ratio (CPR) Doppler, and their relationship with adverse perinatal outcomes in women undergoing routine antenatal care in the third trimester.

Design

Prospective cohort.

Setting

Kagadi Hospital, Uganda.

Population

Non‐anomalous singleton pregnancies.

Methods

Women underwent an early dating ultrasound and a third‐trimester Doppler scan between 32 and 40 weeks of gestation, from 2018 to 2020. We handled missing data using multiple imputation and analysed the data using descriptive methods and a binary logistic regression model.

Main outcome measures

Composite adverse perinatal outcome (CAPO), perinatal death and stillbirth.

Results

We included 995 women. The mean gestational age at Doppler scan was 36.9 weeks (SD 1.02 weeks) and 88.9% of the women gave birth in a health facility. About 4.4% and 5.6% of the UA pulsatility index (PI) and UtA PI were above the 95th percentile, whereas 16.4% and 10.4% of the MCA PI and CPR were below the fifth percentile, respectively. Low CPR was strongly associated with stillbirth (OR 4.82, 95% CI 1.09–21.30). CPR and MCA PI below the fifth percentile were independently associated with CAPO; the association with MCA PI was stronger in small‐for‐gestational‐age neonates (OR 3.75, 95% CI 1.18–11.88).

Conclusion

In late gestation, abnormal UA PI was rare. Fetuses with cerebral blood flow redistribution were at increased risk of stillbirth and perinatal complications. Further studies examining the predictive accuracy and effectiveness of antenatal Doppler ultrasound screening in reducing the risk of perinatal deaths in low‐ and middle‐income countries are warranted.

Tweetable abstract

Blood flow redistribution to the fetal brain is strongly associated with stillbirths in low‐resource settings.

Blood flow redistribution to the fetal brain is strongly associated with stillbirths in low‐resource settings.

This article includes Author Insights, a video abstract available at https://vimeo.com/bjogabstracts/authorinsights17115.

Pre- and postnatal brain hemodynamics in pregnancies at term: correlation with Doppler ultrasound, birthweight, and adverse perinatal outcome

PURPOSE

To elucidate the correlation between pre- and postnatal cerebral Doppler in pregnancies close to term and to explore whether they are associated with perinatal outcome.

MATERIALS AND METHODS

Prospective study on singleton pregnancies at 36-37 weeks of gestation. The primary outcome was a composite score of perinatal morbidity, while secondary outcomes were adverse intra-partum outcome and abnormal acid-base status. All pregnancies underwent ultrasound assessment of umbilical artery (UA), middle cerebral artery (MCA), uterine arteries (UtAs) pulsatility index (PI), and cerebroplacental ratio (CPR). At birth, neonatal MCA PI was measured 72 h from delivery and correlated with prenatal Doppler, primary and secondary outcomes. Fisher's test and multivariate logistic regression analysis were used to analyze the data.

RESULTS

One hundred and sixty-six fetuses with both pre- and postnatal Doppler assessment of the MCA were included in the study. The risk of composite perinatal morbidity was higher in fetuses (OR: 5.7, 95% CI 2.2-14.6) and newborns (OR: 4.1, 95% CI 1.8-9.6) with fetal MCA PI < 10th centile. Likewise, the incidence of abnormal acid-base status was higher both in fetuses (20 versus 4.2%, p = .026) and newborns (17.1 versus 3.2%, p = .001) with a low MCA PI before and at birth, respectively. At logistic regression analysis, fetal and neonatal MCAPI were independently associated with composite perinatal morbidity and abnormal acid-base status, but not with adverse intra-partum outcome. In small for gestational age (SGA) fetuses, the incidence of composite perinatal morbidity was higher in fetuses and new-borns presenting compared to those not presenting with an MCA PI < 10th centile (61.5 versus 20%, p = .003 and 52.6% versus 7.1%, p = .008, respectively), while such association was lost when considering non-SGA fetuses.

CONCLUSION

A low MCA PI is associated with adverse perinatal outcome in pregnancies at term and tends to persist after birth.

Gestational age impacts birth to placental weight ratio and umbilical cord oxygen values with implications for the fetal oxygen margin of safety

BACKGROUND

We determined the impact of gestational age (GA) from near term to term to post-term on birth/placental weight ratio and cord oxygen values with implications for placental transport efficiency for oxygen, fetal O₂ consumption relative to delivery or fractional O₂ extraction, and oxygen margin of safety.

MATERIALS AND METHODS

A hospital database was used to obtain birth/placental weight ratios, cord PO₂ and other information on patients delivering between Jan 1, 1990 and Jun 15, 2011 with GA > 34 completed weeks (N = 69,852). Oxygen saturation was calculated from the cord PO₂ and pH data, while fractional O₂ extraction was calculated from the oxygen saturation data. The effect of GA grouping on birth/placental weight ratio, cord PO₂, O₂ saturation, and fractional O₂ extraction values, was examined in all patients adjusting for pregnancy and labor/delivery covariates, and in a subset of low-risk patients.

RESULTS

Birth/placental weight ratio and umbilical venous O₂ values increased with advancing GA, supporting the conjecture of increasing placental transport efficiency for oxygen. However, umbilical arterial O₂ values decreased while fractional O₂ extraction increased with successive GA groupings, indicating that fetal O₂ consumption must be increasing relative to delivery.

CONCLUSIONS

Fetal O₂ consumption can be seen as ever 'outgrowing' O₂ delivery over the last weeks of pregnancy and leading to a continued lowering in systemic oxygen levels. While this lowering in oxygen may trigger feedback mechanisms with survival benefit, the 'oxygen margin of safety' will also be lowered increasing perinatal morbidity and mortality which appear to be hypoxia related.

A survey of current practice in reporting third trimester fetal biometry and Doppler in Australia and New Zealand

Introduction

Inconsistent reporting practices in third trimester ultrasound, the choice of reference charts in particular, have the potential to misdiagnose abnormal fetal growth. But this may lead to unnecessary anxiety and confusion amongst patients and clinicians and ultimately influence clinical management. Therefore, we sought to determine the extent of variability in choice of fetal biometry and Doppler reference charts and reporting practices in Australia and New Zealand.

Methods

Clinicians performing and/or reporting obstetric ultrasound were invited to answer questions about fetal biometry and Doppler charts in a web-based survey.

Results

At least four population-based charts are in current use. The majority of respondents (78%) report the percentile for known gestational age (GA) alongside measurements and 63% using a cut-off of estimated fetal weight (EFW) < 10^th percentile when reporting small for gestational age (SGA) and/or fetal growth restriction (FGR). The thresholds for the use of fetal and maternal Doppler in third trimester ultrasound varied in terms of the GA, EFW cut-off, and how measures were reported. The majority of respondents were not sure of which Doppler charts were used in their practice.

Conclusion

This survey revealed inconsistencies in choice of reference chart and reporting practices. The potential for misdiagnosis of abnormal fetal growth remains a significant issue.

Fetal cerebral blood-flow redistribution: analysis of Doppler reference charts and association of different thresholds with adverse perinatal outcome

OBJECTIVES

First, to compare published Doppler reference charts of the ratios of flow in the fetal middle cerebral and umbilical arteries (i.e. the cerebroplacental ratio (CPR) and umbilicocerebral ratio (UCR)). Second, to assess the association of thresholds of CPR and UCR based on these charts with short-term composite adverse perinatal outcome in a cohort of pregnancies considered to be at risk of late preterm fetal growth restriction.

METHODS

Studies presenting reference charts for CPR or UCR were searched for in PubMed. Formulae for plotting the median and the 10^th percentile (for CPR) or the 90^th percentile (for UCR) against gestational age were extracted from the publication or calculated from the published tables. Data from a prospective European multicenter observational cohort study of singleton pregnancies at risk of fetal growth restriction at 32 + 0 to 36 + 6 weeks' gestation, in which fetal arterial Doppler measurements were collected longitudinally, were used to compare the different charts. Specifically, the association of UCR and CPR thresholds (CPR < 10^th percentile or UCR ≥ 90^th percentile and multiples of the median (MoM) values) with composite adverse perinatal outcome was analyzed. The association was also compared between chart-based thresholds and absolute thresholds. Composite adverse perinatal outcome comprised both abnormal condition at birth and major neonatal morbidity.

RESULTS

Ten studies presenting reference charts for CPR or UCR were retrieved. There were large differences between the charts in the 10^th and 90^th percentile values of CPR and UCR, respectively, while median values were more similar. In the gestational-age range of 28-36 weeks, there was no relationship between UCR or CPR and gestational age. From the prospective observational study, 856 pregnancies at risk of late-onset preterm fetal growth restriction were included in the analysis. The association of abnormal UCR or CPR with composite adverse perinatal outcome was similar for percentile thresholds or MoM values, as calculated from the charts, and for absolute thresholds, both on univariable analysis and after adjustment for gestational age at measurement, estimated fetal weight MoM and pre-eclampsia. The adjusted odds ratio for composite adverse perinatal outcome was 3.3 (95% CI, 1.7-6.4) for an absolute UCR threshold of ≥ 0.9 or an absolute CPR threshold of < 1.11 (corresponding to ≥ 1.75 MoM), and 1.6 (95% CI, 0.9-2.9) for an absolute UCR threshold of ≥ 0.7 to < 0.9 or an absolute CPR threshold of ≥ 1.11 to < 1.43 (corresponding to ≥ 1.25 to < 1.75 MoM).

CONCLUSIONS

In the gestational-age range of 32 to 36 weeks, adjustment of CPR or UCR for gestational age is not necessary when assessing the risk of adverse outcome in pregnancies at risk of fetal growth restriction. The adoption of absolute CPR or UCR thresholds, independent of reference charts, is feasible and makes clinical assessment simpler than if using percentiles or other gestational-age normalized units. The high variability in percentile threshold values among the commonly used UCR and CPR reference charts hinders reliable diagnosis and clinical management of late preterm fetal growth restriction. © 2021 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Doppler ultrasound in pregnancy - quality requirements of DEGUM and clinical application (part 2)

This second part on Doppler sonography in prenatal medicine and obstetrics reviews its clinical applications. While this has not become the initially anticipated screening tool, it is used for the diagnosis and surveillance of a variety of fetal pathologies. For example, the sonography-based determination of uterine artery blood flow indices is an important parameter for the first trimester multimodal preeclampsia risk assessment, increasing accuracy and providing indication for the prophylactic treatment with aspirin. It also has significant implications for the diagnosis and surveillance of growth-restricted fetuses in the second and third trimesters through Doppler-sonographic analysis of umbilical artery, middle cerebral artery and ductus venosus. Here, especially the hemodynamics of the ductus venosus provides a critical criterium for birth management of severe, early-onset FGR before 34 + 0 weeks of gestation. Further, determination of maximum blood flow velocity of the middle cerebral artery is a central parameter in fetal diagnosis of anemia which has been significantly improved by this analysis. However, it is important to note that the mentioned improvements can only be achieved through highest methodological quality. Importantly, all these analyses are also applied to twins and higher order multiples. Here, for the differential diagnosis of specific complications such as TTTS, TAPS and TRAP, the application of Doppler sonography has become indispensable. To conclude, the successful application of Doppler sonography requires both exact methodology and precise pathophysiological interpretation of the data.

Ultrasound Diagnosis of the Small and Large Fetus

Antenatal imaging is crucial in the management of high-risk pregnancies. Accurate dating relies on acquisition of reliable and reproducible ultrasound images and measurements. Quality image acquisition is necessary for assessing fetal growth and performing Doppler measurements to help diagnose pregnancy complications, stratify risk, and guide management. Further research is needed to ascertain whether current methods for estimating fetal weight can be improved with 3-dimensional ultrasound or magnetic resonance imaging; optimize dating with late initiation of prenatal care; minimize under-diagnosis of fetal growth restriction; and identify the best strategies to make ultrasound more available in low-income and middle-income countries.

Diagnostic Accuracy of Doppler Ultrasound in Predicting Perinatal Outcome in Appropriate for Gestational Age Fetuses: A Prospective Study

OBJECTIVE

 To elucidate the role of Doppler ultrasound in predicting perinatal outcome in appropriate for gestational age (AGA) fetuses at term.

MATERIAL AND METHODS

 Prospective study carried out in a dedicated research ultrasound clinic. The inclusion criterion was AGA fetuses, defined as those with an estimated fetal weight between the 10th and 90th percentile, at 36 + 0-37 + 6 weeks of gestation. The primary outcome was a composite score of adverse perinatal outcome including either adverse intrapartum events or abnormal acid-base status at birth. Secondary outcomes were the individual components of the primary outcome. The Doppler parameters explored were umbilical artery (UA) PI, middle cerebral artery (MCA) PI, uterine arteries (UtA) PI and cerebroplacental ratio (CPR). Attending clinicians were blinded to Doppler findings. Logistic regression and ROC curve analyses were used to analyze the data.

RESULTS

 553 AGA fetuses were included. There was no difference in mean UA PI (p = 0.486), MCA PI (p = 0.621), CPR (p = 0.832) and UtA PI (p = 0.611) between pregnancies complicated by composite perinatal morbidity compared to those not complicated by composite perinatal morbidity. In pregnancies complicated by adverse intrapartum outcome, the mean MCA PI (1.47 ± 0.4 vs 1.61 ± 0.4, p = 0.0039) was lower compared to the control group, while there was no difference in UA PI (p = 0.758), CPR (p = 0.108), and UtA PI (p = 0.177). Finally, there was no difference in any of the Doppler parameters explored between AGA fetuses with abnormal acid-base status at birth compared to those without abnormal acid-base status at birth. In the logistic regression analysis, UA PI, MCA PI, CPR, UtA PI, EFW and AC percentiles were not independently associated with composite adverse outcome, adverse intrapartum outcome or abnormal acid-base status at birth in non-SGA fetuses. The diagnostic performance of all of these Doppler parameters for predicting composite adverse outcome, adverse intrapartum outcome and abnormal acid-base status was poor.

CONCLUSION

 Cerebroplacental and maternal Doppler is not associated with or predictive of adverse pregnancy outcome in AGA fetuses close to term.

Assessment of fetal Doppler parameters in pregnant women with COVID-19 infection: a prospective case-control study

OBJECTIVES

To investigate the effect of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on fetal Doppler parameters.

METHODS

This was a prospective case-control study conducted in Ankara City Hospital with confirmed SARS-CoV-2 infected pregnants between August 1, 2020 and October 1, 2020. There were 54 COVID-19 confirmed pregnant women and 97 age-matched pregnant women as a control group between 28 and 39 weeks. Infection was confirmed based on positive real-time polymerase-chain reaction results. Demographic features, uterine artery (right, left), umblical artery, middle cerebral artery, ductus venosus, cerebro-placental ratio, and cerebral-placental-uterine ratio Doppler parameters were investigated in both groups.

RESULTS

Two groups were similar in terms of demographic features and no difference was found for fetal Doppler parameters.

CONCLUSIONS

COVID-19 seems to have no adverse effect on fetoplacental circulation in mild and moderate patients during the acute phase of the infection.

Heterogeneity in defining fetal corpus callosal pathology: systematic review

OBJECTIVE

Fetal anomalies of the corpus callosum (CC) have been reported in the prenatal imaging literature since 1985, and, especially when isolated, pose challenges for both the patient and fetal medicine specialist. The purpose of this study was to review systematically the literature on prenatally diagnosed abnormalities of the CC, focusing on the terminology used to describe abnormalities other than complete agenesis of the CC, and to assess the heterogeneity of the nomenclature and definitions used.

METHODS

This study was conducted in accordance with the PRISMA statement for reporting systematic reviews. A literature search was performed to identify prospective or retrospective case series or cohort studies, published in English, French, Italian, German or Spanish, reporting fetal imaging findings and describing anomalies of the CC. Quality and risk of bias of the studies were evaluated using the Newcastle-Ottawa scale and a modification of the scale developed by Conde-Agudelo et al. for other fetal imaging studies. The data extracted included the number of patients, the number of different anomalies identified, the descriptive names of the anomalies, and, where applicable, the definitions of the anomalies, the number of cases of each type of anomaly and the biometric charts used. Secondary tests used to confirm the diagnosis, as well as the postnatal or post-termination tests used to ascertain the diagnosis, were also recorded.

RESULTS

The search identified 998 records, and, after review of titles and abstracts and full review of 45 papers, 27 studies were included initially in the review, of which 24 were included in the final analysis. These 24 studies had a broad range of quality and risk of bias and represented 1135 cases of CC anomalies, of which 49% were complete agenesis and the remainder were described using the term partial agenesis or nine other terms, of which five had more than one definition.

CONCLUSIONS

In comparison to the postnatal literature, in the prenatal literature there is much greater heterogeneity in the nomenclature and definition of CC anomalies other than complete agenesis. This heterogeneity and lack of standard definitions in the prenatal literature make it difficult to develop large multicenter pooled cohorts of patients who can be followed in order to develop a better understanding of the genetic associations and neurodevelopmental and psychological outcomes of patients with CC anomalies. As this information is important to improve counseling of these patients, a good first step towards this goal would be to develop a simpler categorization of prenatal CC anomalies that matches better the postnatal literature. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

Fetal umbilical artery Doppler as a tool for universal third trimester screening: A systematic review and meta-analysis of diagnostic test accuracy

The objective of this study was to investigate the accuracy of universal third trimester umbilical artery (UA) Doppler to predict adverse pregnancy outcome at term. We searched Medline, EMBASE, the Cochrane library and ClinicalTrials.gov from inception to October 2020 and we also analyzed previously unpublished data from a prospective cohort study of nulliparous women, the Pregnancy Outcome Prediction (POP) study. We included studies that performed a third-trimester ultrasound scan in unselected, low or mixed risk populations, excluding studies which only included high risk pregnancies. Meta-analysis was performed using the hierarchal summary receiver operating characteristic curve (HSROC) analysis and bivariate logit-normal models. We identified 13 studies (including the POP study) involving 67,764 pregnancies which met our inclusion criteria. The overall quality was variable and only six studies (N = 5777 patients) blinded clinicians to the UA Doppler result. The summary sensitivity and positive likelihood ratio (LR) for small for gestational age (SGA; birthweight <10th centile) were 21.7% (95% CI 13.2-33.6%) and 2.65 (95% CI 1.89-3.72) respectively. The summary positive LR for NICU admission and metabolic acidosis were 1.35 (95% CI 0.93-1.97) and 1.34 (95% CI 0.86-2.08) respectively. The results were similar in the POP study: associations with SGA (positive LR 2.66 [95% CI 2.11-3.36]) and severe SGA (birthweight <3rd centile; positive LR 3.27 [95% CI 2.29-4.68]) but no statistically significant association with neonatal morbidity. We conclude that third trimester UA Doppler has moderate predictive accuracy for small for gestational age but not for indicators of neonatal morbidity in unselected and low risk pregnancies.

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.

Sex differences in fetal Doppler parameters during gestation

BACKGROUND

Fetal sex is known to affect pregnancy outcomes. In current clinical practice, monitoring of fetal well-being is based on Doppler ultrasound measurements of major placental and fetal vessels. The objective of this study was to investigate the effect of fetal sex on Doppler parameters throughout gestation in healthy pregnancy.

METHODS

A prospective study was conducted in 240 pregnant women with ultrasound examinations at a 4-weekly interval between 12 and 38 weeks of gestation. Pulsed Doppler spectra were collected for the umbilical arteries (UAs), middle cerebral artery (MCA), descending abdominal aorta (DAo), and ductus venosus (DV). Linear mixed effects models were used to determine if the pulsatility indices (PIs) of these vessels depended on gestational age and fetal sex.

RESULTS

While there were no differences in the MCA PI and DV PIV over gestation between female and male fetuses, the trajectory of the UA and DAo PIs differed by fetal sex (p = 0.02 and p = 0.01, respectively).

CONCLUSIONS

Doppler ultrasound parameters were found to be dependent on fetal sex for some vessels and not for others in healthy pregnancies. Further investigations are needed to understand the physiological mechanisms for these sex differences and the relevance for disease processes in pregnancy.

The ability of various cerebroplacental ratio thresholds to predict adverse neonatal outcomes in term fetuses exhibiting late-onset fetal growth restriction

OBJECTIVES

Our primary aim was to evaluate the ability of various cerebroplacental ratio (CPR) reference values suggested by the Fetal Medicine Foundation to predict adverse neonatal outcomes in term fetuses exhibiting late-onset fetal growth restriction (LOFGR). Our secondary aim was to evaluate the effectiveness of other obstetric Doppler parameters used to assess fetal well-being in terms of predicting adverse neonatal outcomes.

METHODS

This was a retrospective cohort study of 317 pregnant women diagnosed with LOFGR at 37-40 weeks of gestation between January 1, 2016, and September 1, 2019. Receiver operating characteristic (ROC) curves were drawn to determine the predictive performance of CPR <1, CPR <5th or <10th percentile, and umbilical artery pulsatility (PI) >95th percentile in terms of predicting adverse neonatal outcomes.

RESULTS

Pregnant women exhibiting LOFGR who gave birth in our clinic during the study period at a mean of 38 gestational weeks (minimum 37+0; maximum 40+6 weeks); the median CPR was 1.51 [interquartile range (IQR) 1.12-1.95] and median birthweight 2,350 g (IQR 2,125-2,575 g). The CPR <5th percentile best predicted adverse neonatal outcomes [area under the curve (AUC) 0.762, 95% confidence interval (CI) 0.672-0.853, p<0.0001] and CPR <1 was the worst predictor (AUC 0.630, 95% CI 0.515-0.745, p=0.021). Of other Doppler parameters, neither the umbilical artery systole/diastole ratio nor the mid-cerebral artery to peak systolic velocity ratio (MCA-PSV) predicted adverse neonatal outcomes (AUC 0.598, 95% CI 0.480-0.598, p=0.104; AUC 0.521, 95% CI 0.396-0.521, p=0.744 respectively).

CONCLUSIONS

The CPR values below the 5th percentile better predicted adverse neonatal outcomes in pregnancies complicated by LOFGR than the UA PI and CPR <1 by using Fetal Medicine Foundation reference ranges.

Clinical impact of Doppler reference charts on management of small-for-gestational-age fetuses: need for standardization

OBJECTIVE

To assess clinical variability in the management of small-for-gestational-age (SGA) fetuses according to different published Doppler reference charts for umbilical artery (UA) and fetal middle cerebral artery (MCA) Doppler indices and cerebroplacental ratio (CPR).

METHODS

We performed a systematic search of MEDLINE, EMBASE, CINAHL and the Web of Science databases from 1954 to 2018 for studies with the sole aim of creating fetal Doppler reference values for UA, MCA and CPR. The top cited articles for each Doppler parameter were included. Variability in Doppler values at the following clinically relevant cut-offs was assessed: UA-pulsatility index (PI) > 95^th percentile; MCA-PI < 5^th percentile; and CPR < 5^th percentile. Variability was calculated for each week of gestation and expressed as the percentage difference between the highest and lowest Doppler value at the clinically relevant cut-offs. Simulation analysis was performed in a cohort of SGA fetuses (n = 617) to evaluate the impact of this variability on clinical management.

RESULTS

From a total of 40 studies that met the inclusion criteria, 19 were analyzed (13 for UA-PI, 10 for MCA-PI and five for CPR). Wide discrepancies in reported Doppler reference values at clinically relevant cut-offs were found. MCA-PI showed the greatest variability, with differences of up to 51% in the 5^th percentile value at term. Variability in the 95^th percentile of UA-PI and the 5^th percentile of CPR at each gestational week ranged from 21% to 41% and 15% to 33%, respectively. As expected, on simulation analysis, these differences in Doppler cut-off values were associated with significant variation in the clinical management of SGA fetuses, despite using the same protocol.

CONCLUSIONS

The choice of Doppler reference chart can result in significant variation in the clinical management of SGA fetuses, which may lead to suboptimal outcomes and inaccurate research conclusions. Therefore, an attempt to standardize fetal Doppler reference ranges is needed. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Sex-specific reference ranges of cerebroplacental and umbilicocerebral ratios: longitudinal study

OBJECTIVES

Observational studies have shown that low cerebroplacental ratio (CPR) values predict an increased risk of adverse perinatal outcome. The inverse ratio, i.e. the umbilicocerebral ratio (UCR), has been suggested to be a better predictor as it rises with increasing degree of fetal compromise. However, longitudinal reference ranges for UCR have not been established, and whether gestational-age-dependent changes in CPR or UCR differ between male and female fetuses has not been studied. Thus, the aims of this study were to investigate sex-specific, gestational-age-associated serial changes in CPR and UCR during the second half of pregnancy and to establish longitudinal reference ranges.

METHODS

This was a secondary analysis of prospectively collected data from a dual-center longitudinal observational cohort study of low-risk singleton pregnancies. Doppler blood-flow velocity waveforms were obtained serially from the umbilical artery (UA) and fetal middle cerebral artery (MCA) from 19-41 weeks' gestation, and pulsatility indices (PIs) were determined. CPR and UCR were calculated as the ratios MCA-PI/UA-PI and UA-PI/MCA-PI, respectively. The course and outcome of pregnancies were recorded, and the sex of the fetus was determined after delivery. Reference intervals for CPR and UCR were constructed using multilevel modeling, and gestational-age-specific Z-scores in male and female fetuses were compared.

RESULTS

Of a total of 299 pregnancies enrolled, 284 (148 male and 136 female fetuses) were included in the final analysis, and 979 paired measurements of UA-PI and MCA-PI were used to construct sex-specific longitudinal reference intervals. The relationship of both CPR and UCR with gestational age was U-shaped, but in opposite directions. There was a small but significant difference in Z-scores of CPR and UCR between male and female fetuses throughout the second half of pregnancy (P = 0.007).

CONCLUSIONS

We have established longitudinal reference ranges for CPR and UCR suitable for serial monitoring, with the possibility of refining assessment by using fetal sex-specific ranges and conditioning by a previous measurement. The clinical significance of such refinements needs further evaluation. © 2019 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of the International Society of Ultrasound in Obstetrics and Gynecology.

Prescriptive Reference Standards of Third-Trimester Cerebroplacental Ratio and Its Physiological Determinants

OBJECTIVE

To construct valid reference standards reflecting optimal cerebroplacental ratio and to explore its physiological determinants.

METHODS

A cohort of 391 low-risk pregnancies of singleton pregnancies of nonmalformed fetuses without maternal medical conditions and with normal perinatal outcomes was created. Doppler measurements of the middle cerebral artery and umbilical artery were performed at 24-42 weeks. Reference standards were produced, and the influence of physiological determinants was explored by nonparametric quantile regression. The derived standards were validated in a cohort of 200 low-risk pregnancies.

RESULTS

Maternal body mass index was significantly associated with the 5th centile of the cerebroplacental ratio. For each additional unit of body mass index, the 5th centile was on average 0.014 lower. The derived 5th, 10th, and 50th centiles selected in the validation cohort were 5, 9.5, and 51% of the measurements.

CONCLUSIONS

This study provides methodologically sound prescriptive standards and suggests that maternal body mass index is a determinant of a cutoff commonly used for decision-making.