The vertebroplacental ratio as an alternative to the cerebroplacental ratio in the evaluation of the fetus at the end of pregnancy

Which is the best ultrasound parameter for the prediction of adverse perinatal outcome within 1 day of delivery?

OBJECTIVE

To compare the accuracies of several sonographic parameters for the prediction of adverse perinatal outcome (APO) prior to delivery.

METHODS

This was a prospective study of fetuses attending the day hospital unit of a tertiary referral hospital that were scanned at 34-41 weeks and gave birth within 24 h of examination. APO was defined as a composite of abnormal intrapartum fetal heart rate or intrapartum fetal scalp pH < 7.20 requiring urgent cesarean section, neonatal umbilical cord pH < 7.10, 5' Apgar score <7 and postpartum admission to neonatal or pediatric intensive care units. The accuracies of the middle cerebral, vertebral and umbilical arteries pulsatility index multiples of the median (MoM), the cerebroplacental and vertebroplacental ratios MoM and the EFW in centiles for the prediction of APO was evaluated by means of ROC curves and logistic regression analysis.

RESULTS

A total of 2140 fetuses were prospectively scanned, however only 182 entered into spontaneous or induced labor and were delivered within 24 h of examination. In this group, MCA PI MoM was the best predictor of APO (AUC = 0.76, 95% CI 0.66-0.85, p < .0001) followed by the CPR MoM (AUC = 0.73, 95% CI 0.63-0.84, p < .0001) and the VPR MoM (AUC = 0.71, 95% CI 0.61-0.81, p < .001). Logistic regression analysis indicated that MCA PI MoM was the only independent determinant for the prediction of APO.

CONCLUSION

In a high-risk population of third-trimester fetuses delivering within 24 h of examination, the outcome may be moderately anticipated just with the information provided by the cerebral flow.

Reference values for pulsatility index of fetal anterior and posterior cerebral arteries in prolonged pregnancy

OBJECTIVE

To establish consistent normal reference values for fetal anterior cerebral artery (ACA) and posterior cerebral artery (PCA) pulsatility index (PI) in prolonged pregnancy.

METHODS

This prospective cross-sectional observational study included singleton normal prolonged pregnancies into two study groups according to the gestational age: from 40 + 0 to 40 + 6 and from 41 + 0 to 41 + 6 weeks. The PI was assessed in both anatomical segments of ACA (ACA-S1 and ACA-S2) and of PCA (PCA-S1 and PCA-S2) with color Doppler imaging and pulsed Doppler examination, and reference centiles charts were generated. PI values from the two investigated segments of each vessel were also compared.

RESULTS

Data were obtained in 771 patients: n = 448 in the 40 + 0 and 40 + 6 weeks group, and n = 323 in the 41 + 0 and 41 + 6 weeks group. A moderate decrease in PI was observed as pregnancy progressed. No differences in PI values were found between the two anatomical segments of ACA and PCA.

CONCLUSION

This study provides Doppler reference values for the fetal ACA and PCA PI. It also shows that Doppler examination could be performed indifferently in one of the two anatomical segments of these arteries.

Cerebral Blood Flow Monitoring in High-Risk Fetal and Neonatal Populations

Cerebrovascular pressure autoregulation promotes stable cerebral blood flow (CBF) across a range of arterial blood pressures. Cerebral autoregulation (CA) is a developmental process that reaches maturity around term gestation and can be monitored prenatally with both Doppler ultrasound and magnetic resonance imaging (MRI) techniques. Postnatally, there are key advantages and limitations to assessing CA with Doppler ultrasound, MRI, and near-infrared spectroscopy. Here we review these CBF monitoring techniques as well as their application to both fetal and neonatal populations at risk of perturbations in CBF. Specifically, we discuss CBF monitoring in fetuses with intrauterine growth restriction, anemia, congenital heart disease, neonates born preterm and those with hypoxic-ischemic encephalopathy. We conclude the review with insights into the future directions in this field with an emphasis on collaborative science and precision medicine approaches.

Sleep in the Supine Position during Pregnancy Is Associated with Fetal Cerebral Redistribution

The supine sleep position in late pregnancy is a major risk factor for stillbirth, with a population attributable risk of 5.8% and one in four pregnant women reportedly sleeping in a supine position. Although the mechanisms linking the supine sleep position and late stillbirth remain unclear, there is evidence that it exacerbates pre-existing maternal sleep disordered breathing, which is another known risk factor for adverse perinatal outcomes. Given that maternal sleep position is a potentially modifiable risk factor, the aim of this study was to characterize and correlate uteroplacental and fetal hemodynamics, including cardiac function, in a cohort of women with apparently uncomplicated pregnancies with their nocturnal sleep position. This was a prospective observational cohort study at an Australian tertiary obstetric hospital. Women were asked to complete a series of questions related to their sleep position in late pregnancy after 35 weeks of completed gestation. They also underwent an ultrasound assessment where Doppler indices of various fetoplacental vessels and fetal cardiac function were measured. Regional cerebral perfusion was also assessed. Pregnancy outcome data was extracted from the electronic hospital database for analysis. A total of 274 women were included in the final analysis. Of these, 78.1% (214/274) reported no supine sleep, and 21.9% (60/274) reported going to sleep in a supine position. The middle cerebral artery, anterior cerebral artery, and vertebral artery pulsatility indices were all significantly lower in the supine sleep cohort, as was the cerebroplacental ratio. There were no significant differences in the mode or indication for delivery or in serious neonatal outcomes, including 5-min Apgar score < 7, acidosis, and neonatal intensive care unit admission between cohorts. Women in the supine cohort were more likely to have an infant with a BW > 90th centile (p = 0.04). This data demonstrates fetal brain sparing in association with the maternal supine sleep position in a low-risk population. This data contributes to the growing body of literature attempting to elucidate the etiological pathways responsible for the association of late stillbirth with the maternal supine sleep position.

Mathematical simulation of Doppler changes in late-onset smallness; progression patterns of cerebral and umbilical anomalies define two types of late-onset fetal growth restriction

OBJECTIVE

To evaluate the progression of Doppler abnormalities in fetuses with late-onset fetal smallness (SGA) that become growth restricted (FGR).

METHODS

524 Doppler examinations of the umbilical and cerebral arteries systems, belonging to 442 late-onset SGA fetuses after week 34, were studied, evaluating by means of the statistical difference with the respective abnormal centiles, the pattern of progression into abnormal Doppler values and the distribution and cumulative sum of Doppler anomalies according to the interval to delivery.

RESULTS

Only one third (33.5%, N = 148) of late-onset SGA fetuses presented Doppler anomalies, suggesting that most were of constitutional origin. The most frequent progression pattern into abnormal Doppler (N = 127, 85.81%) was that in which only one system (umbilical or cerebral) became abnormal. Half of fetuses debuted with abnormal umbilical flow (52%, N = 77) and half with cerebral anomalies (47.97%, N = 71), which were more likely to appear later and at shorter intervals to delivery (p = .007). These progression patters defined two varieties of late-onset FGR (type I and II) with similar outcome but different birth weight centiles (BW centile = 2.51, SD 2.91 versus 3.97, SD 3.17, p < .01).

CONCLUSION

Two thirds of late-onset fetal smallness occurs without hemodynamic changes. In half of the remaining cases an initial cerebral vasodilation defines a group of fetuses with similar outcome but higher BW centile.