Re: Ratio of umbilical and cerebral artery pulsatility indices in assessment of fetal risk: numerator and denominator matter

Longitudinal Doppler Assessments in Late Preterm Fetal Growth Restriction

PURPOSE

 To assess the longitudinal variation of the ratio of umbilical and cerebral artery pulsatility index (UCR) in late preterm fetal growth restriction (FGR).

MATERIALS AND METHODS

 A prospective European multicenter observational study included women with a singleton pregnancy, 32^+ 0-36^+ 6, at risk of FGR (estimated fetal weight [EFW] or abdominal circumference [AC] < 10^th percentile, abnormal arterial Doppler or fall in AC from 20-week scan of > 40 percentile points). The primary outcome was a composite of abnormal condition at birth or major neonatal morbidity. UCR was categorized as normal (< 0.9) or abnormal (≥ 0.9). UCR was assessed by gestational age at measurement interval to delivery, and by individual linear regression coefficient in women with two or more measurements.

RESULTS

 856 women had 2770 measurements; 696 (81 %) had more than one measurement (median 3 (IQR 2-4). At inclusion, 63 (7 %) a UCR ≥ 0.9. These delivered earlier and had a lower birth weight and higher incidence of adverse outcome (30 % vs. 9 %, relative risk 3.2; 95 %CI 2.1-5.0) than women with a normal UCR at inclusion. Repeated measurements after an abnormal UCR at inclusion were abnormal again in 67 % (95 %CI 55-80), but after a normal UCR the chance of finding an abnormal UCR was 6 % (95 %CI 5-7 %). The risk of composite adverse outcome was similar using the first or subsequent UCR values.

CONCLUSION

 An abnormal UCR is likely to be abnormal again at a later measurement, while after a normal UCR the chance of an abnormal UCR is 5-7 % when repeated weekly. Repeated measurements do not predict outcome better than the first measurement, most likely due to the most compromised fetuses being delivered after an abnormal UCR.

Diagnostic performance of cerebroplacental and umbilicocerebral ratio in appropriate for gestational age and late growth restricted fetuses attempting vaginal delivery: a multicenter, retrospective study

BACKGROUND

Cerebroplacental Doppler studies have been advocated to predict the risk of adverse perinatal outcome (APO) irrespective of fetal weight.

OBJECTIVE

To report the diagnostic performance of cerebroplacental (CPR) and umbilicocerebral (UCR) ratios in predicting APO in appropriate for gestational age (AGA) fetuses and in those affected by late fetal growth restriction (FGR) attempting vaginal delivery.

STUDY DESIGN

Multicenter, retrospective, nested case-control study between 1 January 2017 and January 2020 involving five referral centers in Italy and Spain. Singleton gestations with a scan between 36 and 40 weeks and within two weeks of attempting vaginal delivery were included. Fetal arterial Doppler and biometry were collected. The AGA group was defined as fetuses with an estimated fetal weight and abdominal circumference >10th and <90th percentile, while the late FGR group was defined by Delphi consensus criteria. The primary outcome was the prediction of a composite of perinatal adverse outcomes including either intrauterine death, Apgar score at 5 min <7, abnormal acid-base status (umbilical artery pH < 7.1 or base excess of more than -11) and neonatal intensive care unit (NICU) admission. Area under the curve (AUC) analysis was performed.

RESULTS

646 pregnancies (317 in the AGA group and 329 in the late FGR group) were included. APO were present in 12.6% AGA and 24.3% late FGR pregnancies, with an odds ratio of 2.22 (95% CI 1.46-3.37). The performance of CPR and UCR for predicting APO was poor in both AGA [AUC: 0.44 (0.39-0.51)] and late FGR fetuses [AUC: 0.56 (0.49-0.61)].

CONCLUSIONS

CPR and UCR on their own are poor prognostic predictors of APO irrespective of fetal weight.

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.

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.

Comparison between Cerebroplacental Ratio and Umbilicocerebral Ratio in Predicting Adverse Perinatal Outcome in Pregnancies Complicated by Late Fetal Growth Restriction: A Multicenter, Retrospective Study

INTRODUCTION

The role of cerebroplacental ratio (CPR) or umbilicocerebral ratio (UCR) to predict adverse intrapartum and perinatal outcomes in pregnancies complicated by late fetal growth restriction (FGR) remains controversial.

METHODS

This was a multicenter, retrospective cohort study involving 5 referral centers in Italy and Spain, including singleton pregnancies complicated by late FGR, as defined by Delphi consensus criteria, with a scan 1 week prior to delivery. The primary objective was to compare the diagnostic accuracy of the CPR and UCR for the prediction of a composite adverse outcome, defined as the presence of either an adverse intrapartum outcome (need for operative delivery/cesarean section for suspected fetal distress) or an adverse perinatal outcome (intrauterine death, Apgar score <7 at 5 min, arterial pH <7.1, base excess of >-11 mEq/mL, or neonatal intensive care unit admission).

RESULTS

Median CPR absolute values (1.11 vs. 1.22, p = 0.018) and centiles (3 vs. 4, p = 0.028) were lower in pregnancies with a composite adverse outcome than in those without it. Median UCR absolute values (0.89 vs. 0.82, p = 0.018) and centiles (97 vs. 96, p = 0.028) were higher. However, the area under the curve, 95% confidence interval for predicting the composite adverse outcome showed a poor predictive value: 0.580 (0.512-0.646) for the raw absolute values of CPR and UCR, and 0.575 (0.507-0.642) for CPR and UCR centiles adjusted for gestational age. The use of dichotomized values (CPR <1, UCR >1 or CPR <5th centile, UCR >95th centile) did not improve the diagnostic accuracy.

CONCLUSION

The CPR and UCR measured in the week prior delivery are of low predictive value to assess adverse intrapartum and perinatal outcomes in pregnancies with late FGR.