Normogram of umbilical artery Doppler indices in singleton pregnancies in south-western Nigerian women

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.

Fetal Gestational Age Estimation Using Ultrasonic Transverse Cerebellar Diameter in a Sub-Saharan African Population

Background

To explore the relationship between fetal Transverse Cerebellar Diameter (TCD) and menstrual gestational age (GA) and to generate normative references (nomogram) of the fetal TCD in some pregnant women in Southwest Nigeria.

Methods

Four hundred pregnant women with a singleton fetus between 14 and 38 weeks GA were enrolled. The TCD and other biometric parameters (biparietal diameter, head circumference, abdominal circumference, and femur length) as well as the cerebellar appearance were analyzed and correlated with the GA.

Results

The mean TCD increased from 13.3 ± 0.3 mm at 14 weeks to 52.3 ± 3.3 mm at 38 weeks of pregnancy. A strong positive correlation was observed between TCD and GA, which was best represented by a linear regression equation: Predicted GA = 0.557 × TCD + 8.840. The regression analysis indicated a statistically significant strong positive relationship between TCD and GA (r = 0.972 and P < 0.001). The cerebellar appearance based on shape and echogenicity was graded into Grade I: 230 fetuses (57.5%); Grade II: 74 fetuses (18.5%) and Grade III: 96 fetuses (24.0%). Median GA and TCD were 21 weeks and 21.2 mm for Grade I; 29 weeks and 35.5 mm for Grade II; and 35 weeks and 48.1 mm for Grade III, respectively.

Conclusion

The TCD increased in a linear fashion with advancing GA in the evaluated fetuses. The TCD is, therefore, a good marker for GA estimation. There is a gradual ultrasonographic change in fetal cerebellar appearance with advancing gestation.

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.

Comparative study of the umbilical artery Doppler indices of healthy and growth-restricted foetuses in Lagos

Aim of the Study:

This study compared the umbilical artery Doppler indices (UADI) in normal and foetal growth-restricted (FGR) foetuses to determine the relationship between the UADI and pregnancy outcomes.

Materials and Methods:

This was a case-control study that recruited one hundred and eighty pregnant women comprising 90 with FGR pregnancies and 90 with normal pregnancies. Foetal biometric parameters and UADI were measured in all the participants. The UADI and clinical outcomes (preterm delivery, birth weight, perinatal death, etc.) of the normal and FGR foetuses were compared.

Results:

The mean estimated foetal weights of the FGR pregnancies (subjects) and normal pregnancies (controls) were 2.76 ± 0.66 kg and 3.62 ± 0.37 kg, respectively (P < 0.0001). The mean APGAR score at 5 min was 6.93 ± 1.72 for subjects and 8.03 ± 0.94 for controls (P < 0.0001). Abnormal umbilical artery Doppler waveforms were detected: decreased end-diastolic flow in 25 (27.8%), absent end-diastolic in 7 (7.8%) and reversed end-diastolic flow in 4 (4.4%) of the FGR pregnancies. There were 74 (82.2%) preterm deliveries among the subjects, while only 7 (7.8%) of the controls had preterm deliveries. Six deaths (two perinatal and four neonatal deaths) were recorded among the subjects, while no death occurred among the controls.

Conclusion:

Foetuses with FGR showed significantly higher quantitative Doppler indices (increased RI, PI, SD ratio), and a higher prevalence of abnormal umbilical artery waveform pattern (qualitative) than the healthy foetuses (controls).

Comparative analysis of umbilical artery doppler indices of normal and suspected IUGR fetuses in the third trimester

Background

Intrauterine growth restriction (IUGR) is an important cause of perinatal morbidity and mortality, the prevalence of which is six times higher in developing countries. The sequelae of IUGR extend into adulthood with higher risk of neurodegenerative diseases for the patients. Umbilical artery (UA) Doppler is an affordable and noninvasive tool for predicting perinatal outcome in IUGR pregnancies.

Aims

The objective of this study is to compare the predictive ability of UA Doppler ultrasonography in discriminating normal from growth-restricted pregnancies and to find out if there is any relationship between antenatal Doppler indices and perinatal outcomes.

Patients and Methods

This is a cross-sectional study including 100 normal and 100 IUGR-suspected pregnancies, respectively. Each participant had a third trimester UA Doppler scan. Data were analyzed using SPSS version 18.0 (PASW Statistics for Windows, Version 18.0, Chicago: SPSS Inc.). Means were compared using Student's t-test and ANOVA. Tests of relationship and prediction were done using linear regression analysis and receiver operating characteristics. P ≤ 0.05 was considered statistically significant.

Results

As pregnancy advanced, the mean values of UA Doppler indices decreased in normal and IUGR fetuses; however, they were significantly higher in the latter. UA systolic/diastolic (S/D) ratio showed the highest sensitivity (0.80) and specificity (0.91) for predicting IUGR compared to PI and RI. Cutoff values for PI, RI, and S/D ratio were 0.93, 0.67, and 2.93, respectively.

Conclusion

IUGR fetuses had higher UA flow velocimetric indices compared with normal fetuses. UA Doppler study is highly sensitive in the prediction of IUGR.

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.

The cerebroplacental ratio: association with maternal hypertension and proteinuria

Objective

To evaluate the resistive indices (RIs) of the fetal umbilical and middle cerebral arteries, as well as to determine the cerebroplacental ratio (CPR), in fetuses of women with hypertension.

Materials and Methods

This was a comparative cross-sectional study involving 75 pregnant women with pregnancy-induced hypertension (PIH) and 75 apparently healthy pregnant women (control group), all of whom were submitted to Doppler ultrasound examination of the fetal middle cerebral and umbilical arteries between 20 and 40 weeks of gestation. The two groups were compared in terms of the RI of the middle cerebral and umbilical arteries, as well as the CPR. The level of statistical significance was set at p ≤ 0.05.

Results

The mean age was 32.4 ± 4.6 years in the PIH group and 32.6 ± 4.6 years in the control group (p = 0.633). The mean umbilical artery RI was significantly higher in the PIH group than in the control group (0.67 ± 0.14 vs. 0.61 ± 0.08; p = 0.012), whereas the mean middle cerebral artery RI was significantly higher in the control group (0.80 ± 0.05 vs. 0.76 ± 0.08; p = 0.001). Among the women in the PIH group, the mean CPR was significantly lower for those with proteinuria than for those without (1.07 ± 0.26 vs. 1.27 ± 0.22; p = 0.001).

Conclusion

Maternal hypertension during pregnancy appears to be associated with increased fetal umbilical artery RI and reduced fetal middle cerebral artery RI, as well as with a low CPR. In pregnant women, the combination of PIH and proteinuria is also apparently associated with an increased risk of a low CPR.

Prevalence of abnormal umbilical arterial flow on Doppler ultrasound in low-risk and unselected pregnant women: a systematic review

Background

While Doppler ultrasound screening is beneficial for women with high-risk pregnancies, there is insufficient evidence on its benefits and harms in low- and unselected-risk pregnancies. This may be related to fewer events of abnormal Doppler flow, however the prevalence of absent or reversed end diastolic flow (AEDF or REDF) in such women is unknown. In this systematic review, we aimed to synthesise available data on the prevalence of AEDF or REDF.

Methods

We searched PubMed, Embase, CINAHL, CENTRAL and Global Index Medicus with no date, setting or language restrictions. All randomized or non-randomized studies reporting AEDF or REDF prevalence based on Doppler assessment of umbilical arterial flow > 20 weeks’ gestation were eligible. Two authors assessed eligibility and extracted data on primary (AEDF and REDF) and secondary (fetal, perinatal, and neonatal mortality, caesarean section) outcomes, with results presented descriptively.

Results

A total of 42 studies (18,282 women) were included. Thirty-six studies reported zero AEDF or REDF cases. However, 55 AEDF or REDF cases were identified from just six studies (prevalence 0.08% to 2.13%). Four of these studies were in unselected-risk women and five were conducted in high-income countries. There was limited evidence from low- and middle-income countries.

Conclusions

Evidence from largely observational studies in higher-income countries suggests that AEDF and REDF are rare among low- and unselected-risk pregnant women. There are insufficient data from lower-income countries and further research is required.

Doppler velocimetry indices of human immunodeficiency virus-positive pregnant women and their controls at Aminu Kano Teaching Hospital, Kano

Background

Nigeria is among the countries having a large number of human immunodeficiency virus (HIV)-infected people in Africa with growing number of HIV-positive children, mainly infected by their mothers. Traditional tests diagnose high-risk fetuses very late. Doppler sonography has a potential for detecting high at-risk fetus at a much early stage, so that appropriate measures could be instituted to improve outcomes. This study compared umbilical artery velocimetric parameters among HIV-positive women on highly active antiretroviral therapy (HAART) and their matched controls to determine the possible abnormalities and correlates.

Methodology

This was a comparative study that was conducted among HIV-positive pregnant women and their matched controls (HIV-negative pregnant women matched for gestational age and parity) at Aminu Kano Teaching Hospital. History and physical examination, transabdominal ultrasound examination were done on each subject to obtain the basic obstetric parameters. Detailed evaluations of the umbilical arteries on gray scale and duplex Doppler protocols using a 3.5-MHz curvilinear transducer were also done. The data were analyzed using SPSS Version 19.0. Independent samples t-test was used for continuous data. Chi-square test and Fisher's exact test were used for categorical data. P < 0.05 was considered statistically significant.

Results

The mean age ± standard deviation (SD) was 30.8 ± 5.50 and 27.6 ± 5.34 for HIV and control groups, respectively. The mean amniotic fluid indices and that of estimated fetal weight for the HIV and control groups showed no statistically significant difference between the two groups. The mean (±SD) umbilical artery diameter of the HIV-infected mothers is wider than their negative controls.

Conclusion

The study showed no statistically significant difference between the Doppler indices of HIV-positive pregnant women on HAART and their matched controls.

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.

Normative references and clinical correlates of fetal umbilical artery Doppler indices in southwestern Nigeria

OBJECTIVE

To derive normative references for umbilical artery (UA) Doppler indices, including pulsatility index (PI), resistance index (RI), and systolic/diastolic (SD) ratio, for singleton pregnancies in Ile-Ife, Nigeria, and compare them with reference values from other populations.

METHODS

A longitudinal study involving 415 women with a singleton fetus at 26-40 gestational weeks attending Obafemi Awolowo University Hospital, Ile-Ife, between July 2015 and March 2019. Fetal UA PI, RI, and SD ratio were measured every 4 weeks until delivery. Reference values from the 2.5th to the 97.5th centiles were derived from 1375 measurements. Correlations between indices and bio-demographic characteristics were assessed; regression equations were generated.

RESULTS

The RI, PI, and SD ratio decreased by 0.013, 0.027, and 0.71, respectively, for each additional week of pregnancy. There was a negative correlation between the three indices and birthweight (P<0.001), but not maternal parity, age, or fetal gender. Regression equations for RI, PI, and SD ratio were, respectively, 1.004 - 0.013x, 1.78 - 0.027x, and 4.77 - 0.71x, where x is gestational age (weeks).

CONCLUSION

The derived normative references for fetal UA Doppler indices are recommended for monitoring high-risk pregnancies in Nigeria. The indices are comparable to those derived from Norwegian, Thai, and British cohorts.

Fetal Gestational Age Determination using Ultrasound Placental Thickness

BACKGROUND

The purposes of this study are to sonographically measure the placental thickness (PT) in normal fetuses; to correlate it with gestational age (GA), fetal growth parameters, and estimated fetal weight (EFW); and to design a nomogram for the derived PT measurements.

METHODS

This was a hospital-based cross-sectional study on 400 women with apparently normal pregnancy within the age range of 18-45 years recruited from the Antenatal Clinic of our hospital. The fetal GA was estimated by the last menstrual period (LMP). The fetal growth parameters were determined using standard sonographic methods while the PT was measured at the level of the umbilical cord insertion site. PT was then correlated with GA, fetal growth parameters, and the EFW.

RESULTS

The mean PT (mean ± standard deviation) in the 1st, 2nd, 3rd trimesters and the whole duration of pregnancy were 14.5 ± 0.3 mm, 24.6 ± 3.9 mm, 34.8 ± 2.8 mm, and 29.6 ± 7.1 mm, respectively. PT ranged from 13.5 ± 1.9 mm at 11 weeks to 39.1 ± 0.6 mm at 40 weeks. PT (in mm) had a linear relationship and a statistically significant positive correlation with GA (in weeks) in all the trimesters, with most significant correlation recorded in the 2nd trimester (r = 0.79). There was also a statistically significant positive correlation between PT and the fetal growth parameters (biparietal diameter, head circumference, abdominal circumference, femur length and crown-rump length), and EFW. PT nomogram was developed from 11 to 40 weeks of gestation using a scatter plot with 95% confidence interval for our locality.

CONCLUSION

PT has a linear relationship with GA, fetal growth parameters, and EFW and it can be used along with other fetal growth parameters to increase the accuracy for predicting GA in normal pregnancies, especially when the subject is not sure of or does not know her LMP.

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

OBJECTIVE

To assess studies reporting reference ranges for umbilical artery (UA) and fetal middle cerebral artery (MCA) Doppler indices and cerebroplacental ratio (CPR), using a set of predefined methodological quality criteria for study design, statistical analysis and reporting methods.

METHODS

This was a systematic review of observational studies in which the primary aim was to create reference ranges for UA and MCA Doppler indices and CPR in fetuses of singleton gestations. A search for relevant articles was performed in MEDLINE, EMBASE, CINAHL, Web of Science (from inception to 31 December 2016) and references of the retrieved articles. Two authors independently selected studies, assessed the risk of bias and extracted the data. Studies were scored against a predefined set of independently agreed methodological criteria and an overall quality score was assigned to each study. Linear multiple regression analysis assessing the association between quality scores and study characteristics was performed.

RESULTS

Thirty-eight studies met the inclusion criteria. The highest potential for bias was noted in the following fields: 'ultrasound quality control measures', in which only two studies demonstrated a comprehensive quality-control strategy; 'number of measurements taken for each Doppler variable', which was apparent in only three studies; 'sonographer experience', in which no study on CPR reported clearly the experience or training of the sonographers, while only three studies on UA Doppler and four on MCA Doppler did; and 'blinding of measurements', in which only one study, on UA Doppler, reported that sonographers were blinded to the measurement recorded during the examination. Sample size estimations were present in only seven studies. No predictors of quality were found on multiple regression analysis. Reference ranges varied significantly with important clinical implications for what is considered normal or abnormal, even when restricting the analysis to the highest scoring studies.

CONCLUSIONS

There is considerable methodological heterogeneity in studies reporting reference ranges for UA and MCA Doppler indices and CPR, and the resulting references have important implications for clinical practice. There is a need for the standardization of methodologies for Doppler velocimetry and for the development of reference standards, which can be correctly interpreted and applied in clinical practice. We propose a set of recommendations for this purpose. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.