Colour Doppler Ultrasound Evaluation of Umbilical Artery and Middle Cerebral Artery in Suspected Intrauterine Growth Restriction Foetuses

Introduction

Intrauterine Growth Restriction (IUGR) is a pathological condition strongly related to the development and function of the uteroplacental and fetoplacental circulation and is related with an higher risk of perinatal mortality, morbidity and impaired neurodevelopment.¹ Placental insufficiency most commonly leads to IUGR, which is an important perinatal complication on the account of associated high perinatal mortality and morbidity. It is crucial to identify placental insufficiency early so that its hazards can be minimized.

Doppler Ultrasonography (USG) allows a better understanding of the vascular changes and therefore, has become indispensable aid for feto-maternal supervision in high-risk pregnancies.It can be attributed with causing reduction in perinatal mortality and morbidity.¹ Our study was an effort to establish the role of Umbilical Artery (UA) and Middle Cerebral Artery (MCA) indices on Doppler US in predicting perinatal outcome in clinically suspected IUGR pregnancies, and to determine the role of Doppler velocimetry in clinical management of such pregnancies.

Material and Methods

This prospective observational study was conducted over a period of 17 months (November 2019 - March 2021) and included 50 cases. After a regular obstetric ultrasound evaluation, Doppler parameters such as Umbilical Artery and Middle cerebral Artery Pulsatility Indices (PI) were measured. Colour Doppler ultrasound was performed using machine GE LOGIQ F8 having low frequency curvilinear transducer. Follow up Doppler studies were done, if clinically indicated to determine a favourable or a worsening pattern in the Doppler indices. However, only the results of first doppler ultrasound were considered for analysis in our study.

Results

The mean age of pregnant women included in the study was 24.64 ± 3.05 years, with minimum age of 20 years and maximum age of 31 years. The mean gestational age at the first Doppler US examination was 32.91 ± 3.10 weeks; minimum gestational age was 25 weeks and maximum gestational age 38 weeks. The mean Foetal Heart Rate (FHR) was 136.32 ± 13.5; the minimum FHR observed was 108 and maximum 156. The mean Estimated Foetal Weight (EFW) observed was 1.81 ± 0.32; the minimum EFW was 1.2 and maximum 2.5. In the present study, 35 (70.0%) cases were Oligohy dramnios and 15 (30.0%) cases were with adequate amniotic fluid. Twenty six (52%) mothers had Pregnancy Induced Hypertension, and 17 (34%) had anaemia. Twenty three (46%) foetuses had at least one adverse outcome that included six (12%) Intrauterine Deaths (IUD). Of the six IUDs, four cases had diastolic flow reversal and two had absent diastolic flow. In all cases with diastolic flow reversal, IUD of the foetus occurred within seven days of the diagnosis. Of the 44 live births, 10 neonates were admitted to Neonatal ICU. Nine neonates had five min Apgar score of under 7 and 12 babies were born by emergency lower segment caesarean section (LSCS).

There was statistically highly significant difference in mean MCA PI, UA PI and MCA/UA between normal and abnormal perinatal outcome (p<0.01) and (p<0.001). The mean MCA PI was remarkably lower in the abnormal perinatal outcome as compared to normal perinatal outcome. The mean UA PI was significantly higher in the abnormal perinatal outcome as compared to normal perinatal outcome. The mean MCA PI/UA PI was significantly lower in the abnormal perinatal outcome as compared to normal perinatal outcome. If cerebroplacental ratio is <1, it was considered as abnormal.² (Table 1)

The following multiple bar diagram represents comparison of MCA PI, UA PI and MCA/UA between normal and abnormal perinatal outcome.

The data of MCA and UA doppler indices obtained from 50 suspected IUGR cases was plotted on the normogram and scatter diagrams were obtained. The below scatter diagrams show correlation between doppler indices and perinatal outcome.

MCA PI was most sensitive (sensitivity 95.65%). It was more sensitive than either Cerebroplacental Ratio MCA/UA PI (sensitivity 91.3%) or UA PI (sensitivity 91.3%) in predicting any adverse outcome. However, Cerebroplacental Ratio (specificity 81.48%) was more specific compared to UA PI (Specificity 66.6%) and MCA PI (Specificity 63%). Cerebroplacental Ratio (MCA/UA) had highest diagnostic accuracy (86%) compared to UAPI (78%) and MCA PI (78%) when considered alone. Cerebroplacental Ratio (MCA/UA) had highest Positive Predictive Value (PPV=80.8%) compared to UA PI (PPV=70%) and MCA PI (PPV=68.75%) when considered alone. However, UA PI 94.4 had highest Negative Predictive Value (NPV) followed by Cerebroplacental Ratio 91.66% and MCA PI 90.0. (Table 2)

Discussion

Doppler velocimetry of uteroplacental, umbilical and foetal vessels have become an established method for foetal monitoring in day-to-day obstetric practice.³ Circulatory changes reflected in foetal Doppler waveforms can reliably predict adverse perinatal outcome. Several investigators have highlighted the utility of doppler ultrasound of umbilical and foetal vessels for monitoring foetal well-being, IUGR, foetal anaemia, and perinatal outcomes.⁴

Gramellini and co-workersconcluded that when compared either to MCA or UA alone, the cerebroplacental Doppler ratio gave a better predictor of small-for-gestational age (SGA) newborns and abnormal perinatal outcome.⁵ In fact, in predicting those newborns that were SGA, while MCA and UA had diagnostic accuracy of 54.4% and 65.5% respectively. The cereboplacental ratio was way ahead and had a diagnostic accuracy of 70%. The results were more encouraging for detection of adverse perinatal outcome; while diagnostic accuracy of MCA and UA was 78.8% and 83.3% respectively, the diagnostic accuracy of cerebral-placental ratio stood much higher at 90%.

Our study confirms with the findings of Gramellini et al.,that rather than using PIs of MCA and UA separately, better results were obtained when we used MCA/UA PI Ratio.⁵

Chan and colleagues studied 71 high-risk foetuses with weekly UA and MCA Doppler US examinations until delivery.⁶ In 15.5% (11 of 71) of foetuses, there was perinatal mortality or major morbidity. By using the last Doppler US result for analysis, the UA/MCA resistance index ratio when compared with the UA systolic-todiastolic ratio was more sensitive (75% vs 64%) but less specific (60% vs 74%).

Results of the present study confirm with those of Chan et al. that UA Doppler US was a better predictor for each of the individual adverse outcomes when separate analyses were performed.⁶ Sensitivity, specificity, PPV, NPV of UA PI in predicting adverse perinatal outcome were 91.3, 66.6, 70, 94.⁴ respectively in the present study.

Fong and colleagues studied 293 small–for–gestational age foetuses with Doppler US of the UA, MCA, and RA.⁷ They concluded that the MCA pulsatility index (PI) when compared with the UA PI and RA PI was more sensitive (72.4% vs 44.7% and 8.3%), but less specific (58.1% vs 86.6% and 92.6%) in predicting abnormal outcome. Results of the present study confirm with those of Fong et al. that MCA PI had more sensitivity but low specificity in predicting abnormal perinatal outcome.⁷

The present study has not included the doppler of renal artery as that in Fong KW et al. The nomograms we utilized for investigation were from the prospective, observational study by Srikumar and colleagues.8 The present study revealed that doppler study in pregnant women with IUGR played an important role in management and predicting outcome. Along with doppler indices, mainly cerebroplacental ratio and pulsatility index, a valuable method for predicting the perinatal outcome is to measure umbilical artery end diastolic flow. The mortality rate for cases with absent end diastolic flow was 29%. The mortality rate of cases with reversed diastolic flow was very high (100%). There were six IUDs in whom two had absent diastolic flow and four cases had reversal of diastolic flow. IUD occurred within seven days of conclusion in all cases with reversal of diastolic flow. And all the four cases were under 32 weeks. The recommendations for future examination is to include pregnant ladies in second trimester and to distinguish early IUGR by foetal and maternal doppler and its early management to reduce the occurrence of unfavourable perinatal result.

Conclusion

The foetal Doppler indices, in particular, ratios that include measurements from umbilical and middle cerebral artery help in the detection of the IUGR foetuses. In clinically suspected IUGR patients, cerebroplacental ratio (MCA/UA) is a better predictor of abnormal perinatal outcome than MCA PI and UA PI when considered alone. Absent or reversal of diastolic flow in the umbilical artery indicates grave prognosis and high foetal mortality.

Conflict of interest

Nil.

Financial support

Nil.