Can adverse neonatal outcome be predicted in late preterm or term fetal growth restriction?

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.

Clinical monitoring of late fetal growth restriction

Late fetal growth restriction (FGR) poses its own challenges in respect of diagnosis, surveillance and delivery timing. Perinatal morbidity is relatively rare, and mortality extremely unusual, but given that late FGR is much more frequent than early FGR, the burden on neonatal services must not be underestimated. Doppler findings are more subtle than in early FGR, and growth rate rather than absolute fetal size may be important in defining the condition. Though umbilical artery Doppler changes form the basis for triggering delivery: reversed end diastolic flow at 32 weeks, absent at 34 weeks and raised PI at 36 weeks, other modalities of monitoring - for example cardiotocography and cerebral Doppler - are important in surveillance and timing follow up of the condition.

Cell free hemoglobin in the fetoplacental circulation: a novel cause of fetal growth restriction?

Cell free hemoglobin impairs vascular function and blood flow in adult cardiovascular disease. In this study, we investigated the hypothesis that free fetal hemoglobin (fHbF) compromises vascular integrity and function in the fetoplacental circulation, contributing to the increased vascular resistance associated with fetal growth restriction (FGR). Women with normal and FGR pregnancies were recruited and their placentas collected freshly postpartum. FGR fetal capillaries showed evidence of erythrocyte vascular packing and extravasation. Fetal cord blood fHbF levels were higher in FGR than in normal pregnancies ( P < 0.05) and the elevation of fHbF in relation to heme oxygenase-1 suggests a failure of expected catabolic compensation, which occurs in adults. During ex vivo placental perfusion, pathophysiological fHbF concentrations significantly increased fetal-side microcirculatory resistance ( P < 0.05). fHbF sequestered NO in acute and chronic exposure models ( P < 0.001), and fHbF-primed placental endothelial cells developed a proinflammatory phenotype, demonstrated by activation of NF-κB pathway, generation of IL-1α and TNF-α (both P < 0.05), uncontrolled angiogenesis, and disruption of endothelial cell flow alignment. Elevated fHbF contributes to increased fetoplacental vascular resistance and impaired endothelial protection. This unrecognized mechanism for fetal compromise offers a novel insight into FGR as well as a potential explanation for associated poor fetal outcomes such as fetal demise and stillbirth.-Brook, A., Hoaksey, A., Gurung, R., Yoong, E. E. C., Sneyd, R., Baynes, G. C., Bischof, H., Jones, S., Higgins, L. E., Jones, C., Greenwood, S. L., Jones, R. L., Gram, M., Lang, I., Desoye, G., Myers, J., Schneider, H., Hansson, S. R., Crocker, I. P., Brownbill, P. Cell free hemoglobin in the fetoplacental circulation: a novel cause of fetal growth restriction?

Use of Doppler velocimetry in diagnosis and prognosis of intrauterine growth restriction (IUGR): A Review

Intrauterine growth restriction (IUGR) is a condition which has been difficult to assess at an early stage, resulting in the delivery of children who have poor genetic growth potential. Currently, IUGR classification is based upon the system of ultrasound biometry. Doppler velocimetry allows the measurement of hemodynamic flow of major fetal vessels, comparing the flow indices and patterns of normal and IUGR cases. In this review, the effectiveness of Doppler velocimetry in assessing blood flow in major vessels including the umbilical artery, ductus venosus, and middle cerebral artery was studied for both diagnostic and prognostic screening of IUGR. The umbilical artery is the most frequently studied vessel in Doppler velocimetry due to its accessibility and the strength of its associations with fetal outcomes. Abnormalities in the ductus venosus waveform can be indicative of increased resistance in the right atrium due to placental abnormalities. The middle cerebral artery is the most studied fetal cerebral artery and can detect cerebral blood flow and direction, which is why these three vessels were selected to be examined in this context. A potential mathematical model could be developed to incorporate these Doppler measurements which are indicative of IUGR, in order to reduce perinatal mortality. The purpose of the proposed algorithm is to integrate Doppler velocimetry with biophysical profiling in order to determine the optimal timing of delivery, thus reducing the risks of adverse perinatal outcomes.

Optimal threshold for birth weight discordance: Does knowledge of chorionicity matter?

OBJECTIVE

To establish the optimal threshold of birth weight discordance (BWD) for prediction of stillbirth, perinatal mortality and morbidity in twins born in British Columbia with or without chorionicity information.

STUDY DESIGN

This is a retrospective population-based cohort study of twins born in British Columbia from 2000 to 2010. Data from one hospital was used to adjust for chorionicity. Multivariate generalized estimating equation and receiver operating characteristic curve analyses were performed to evaluate the predictability of BWD in comparison with other fetal anthropometric measurements. Positive likelihood ratio is used to estimate test accuracy. Survival analysis was conducted to take gestational age and other confounders into account.

RESULTS

We analyzed two cohorts, with (pairs=1493) and without (pairs=6328) chorionicity information, of which 1.5% experienced stillbirth, 2.9% suffered perinatal mortality and 22.6% identified with perinatal morbidities. BWD was a significant predictor of stillbirth. Standard receiver operating characteristic curve analysis and survival analysis suggested that BWD of ⩾30% is the optimal thresholds for stillbirth and perinatal mortality irrespective of chorionicity. However, the P-value for predictive accuracy of BWD was nonsignificant for perinatal morbidity, after adjusting for confounding variables engaging multivariate analysis. Sex discordance can be used as a proxy for chorionicity.

CONCLUSION

BWD is a good predictor for stillbirth. A BWD cutoff limit of 30% and higher has optimal accuracy for detecting perinatal mortality.

Dysregulated flow-mediated vasodilatation in the human placenta in fetal growth restriction

Increased vascular resistance and reduced fetoplacental blood flow are putative aetiologies in the pathogenesis of fetal growth restriction (FGR); however, the regulating sites and mechanisms remain unclear. We hypothesised that placental vessels dictate fetoplacental resistance and in FGR exhibit endothelial dysfunction and reduced flow-mediated vasodilatation (FMVD). Resistance was measured in normal pregnancies (n = 10) and FGR (n = 10) both in vivo by umbilical artery Doppler velocimetry and ex vivo by dual placental perfusion. Ex vivo FMVD is the reduction in fetal-side inflow hydrostatic pressure (FIHP) following increased flow rate. Results demonstrated a significant correlation between vascular resistance measured in vivo and ex vivo in normal pregnancy, but not in FGR. In perfused FGR placentas, vascular resistance was significantly elevated compared to normal placentas (58 ± 7.7 mmHg and 36.8 ± 4.5 mmHg, respectively; 8 ml min⁻¹; means ± SEM; P < 0.0001) and FMVD was severely reduced (3.9 ± 1.3% and 9.1 ± 1.2%, respectively). In normal pregnancies only, the highest level of ex vivo FMVD was associated with the lowest in vivo resistance. Inhibition of NO synthesis during perfusion (100 μm l-NNA) moderately elevated FIHP in the normal group, but substantially in the FGR group. Human placenta artery endothelial cells from FGR groups exhibited increased shear stress-induced NO generation, iNOS expression and eNOS expression compared with normal groups. In conclusion, fetoplacental resistance is determined by placental vessels, and is increased in FGR. The latter also exhibit reduced FMVD, but with a partial compensatory increased NO generation capacity. The data support our hypothesis, which highlights the importance of FMVD regulation in normal and dysfunctional placentation.

The (Pulsed-Wave) Doppler Fetal Myocardial Performance Index: Technical Challenges, Clinical Applications and Future Research

Functional cardiovascular assessment is becoming an increasingly important tool in the study of fetal pathology. The myocardial performance index (MPI) is a parameter measuring global myocardial function. Since its introduction, several studies have proposed methods to improve its reproducibility and have constructed normative reference ranges. Fetal heart evaluation using the MPI is technically challenging, requiring specific training and expertise, and a consensus has yet to be reached on the method of delineating the time periods used to calculate the index. Despite these limitations, it has been shown to be a useful and highly sensitive parameter of dysfunction in a number of fetal pathologies. Further research is warranted into the effect of pathology on MPI, parameters of unilateral cardiac strain that utilise MPI, and automation of the MPI to encourage incorporation of the MPI as a useful tool in clinical practice.

IUGR management: new perspectives

AIM OF THE STUDY

Analyzing velocimetric (umbilical artery, UA; ductus venosus, DV; middle cerebral artery, MCA) and computerized cardiotocographic (cCTG) (fetal heart rate, FHR; short term variability, STV; approximate entropy, ApEn) parameters in intrauterine growth restriction, IUGR, in order to detect early signs of fetal compromise. POPULATION STUDY: 375 pregnant women assisted from the 28th week of amenorrhea to delivery and monitored through cCTG and Doppler ultrasound investigation. The patients were divided into three groups according to the age of gestation at the time of delivery, before the 34th week, from 34th to 37th week, and after the 37th week. Data were analyzed in relation to the days before delivery and according to the physiology or pathology of velocimetry. Statistical analysis was performed through the t-test, chi-square test, and Pearson correlation test (P < 0.05). Our results evidenced an earlier alteration of UA, DV, and MCA. The analysis between cCTG and velocimetric parameters (the last distinguished into physiological and pathological values) suggests a possible relation between cCTG alterations and Doppler ones. The present study emphasizes the need for an antenatal testing in IUGR fetuses using multiple surveillance modalities to enhance prediction of neonatal outcome.

Timing of delivery and neonatal outcomes for small-for-gestational-age fetuses

OBJECTIVES

To investigate whether antenatal recognition of small-for-gestational-age (SGA) fetuses with normal maternal and fetal Doppler values delivered after 34 weeks' gestation is associated with changes in the risk of adverse maternal and neonatal outcomes.

METHODS

In this retrospective study, we included 313 singleton SGA fetuses and 313 appropriate-for-gestational-age control fetuses born between 34 and 42 weeks' gestation from 2009 to 2012. Small-for-gestational-age fetuses identified before delivery (n = 124), for whom antenatal surveillance was performed until delivery (estimated fetal weight twice weekly and Doppler evaluation of the fetal compartment once weekly), were compared to those not identified at delivery (n = 189). The latter group did not undergo antenatal surveillance for several reasons (women for whom a sonographic evaluation or gynecologic consultation was not performed in the third trimester and incorrect sonographic biometric evaluation in the third trimester). Main outcome measures were mode of delivery, perinatal complications, and neonatal intensive care unit admission. The risk of serious fetal complications was assessed by cross-tabulation analysis adjusted for gestational age and degree of SGA.

RESULTS

Prenatally recognized SGA fetuses were smaller and delivered earlier than unrecognized SGA fetuses (P< .05). Fetal acidemia (pH <7.10) was significantly more common in unrecognized SGA fetuses (3.7% versus 0%). Small-for-gestational-age fetuses at or below the 3rd percentile were more commonly recognized prenatally and hospitalized in the neonatal intensive care unit. Unrecognized SGA fetuses also had worse fetal outcomes compared to controls (P< .05). Recognized and unrecognized SGA fetuses were born significantly more frequently by cesarean delivery (P < .05). No significant differences in perinatal outcomes were found between recognized SGA deliveries with or without medical induction.

CONCLUSIONS

Antenatal recognition of SGA fetuses delivered after 34 weeks' gestation might improve perinatal outcomes. Medical induction of labor did not modify neonatal outcomes among prenatally recognized SGA fetuses.

Umbilical artery peak systolic velocity measurements for prediction of perinatal outcome among IUGR fetuses

BACKGROUND

To evaluate the role of umbilical artery (UA) peak systolic velocity (PSV) measurements in the prediction of perinatal outcome in fetuses with intrauterine growth restriction (IUGR).

METHODS

A prospective study was performed, including patients with a suspected diagnosis of IUGR. Exclusion criteria were multiple gestations, unreliable gestational age, and known fetal malformations. Doppler measurements of the UA and middle cerebral artery (MCA) were recorded.

RESULTS

Seventy-two patients were enrolled and a total of 192 Doppler measurements were performed between 24 and 39 weeks' gestation. Mean gestational age at delivery was 36.9 ± 2.7 days and mean birth weight was 2,166 ± 497 grams. Nine patients (12.5%) had oligohydramnios; 50 (69.4%) delivered preterm (<37 weeks), and 26 underwent a cesarean section, of those 7 (29.2%) cesarean sections were for a nonreassuring fetal heart rate tracing. Fifty-one (70.8%) neonates were actually small for gestational age. No correlation was found between UA-PSV and MCA-PSV to perinatal outcome. Correlation was found between UA pulsatility index and cerebroplacental ratio to perinatal outcome before 34 weeks' gestation.

CONCLUSIONS

UA PSV measurements do not correlate with adverse perinatal outcome. A correlation exists between UA pulsatility index and cerebroplacental ratio and perinatal outcome prior to 34 weeks' gestation. It seems that UA PSV and MCA PSV do not contribute to the management of fetuses with IUGR.

Modified myocardial performance index is not affected in fetuses with an isolated echogenic focus in the left ventricle

OBJECTIVES

We prospectively investigated the efficacy of modified myocardial performance index (mod-MPI) in the assessment of cardiac functions in fetuses with and without an isolated hyperechogenic focus (IHF) in the left ventricle and compared with conventional fetal echocardiography.

METHODS

The study group consisted of 50 fetuses with only an IHF in the left ventricle, without any other cardiac or extracardiac anomalies; 50 fetuses without IHF served as controls. All fetal echocardiographic studies were performed between 20th and 24th weeks of gestation. Left ventricular functions were evaluated with both conventional echocardiographic methods (peak velocity of the aortic valve, mitral E/A ratio, fractional shortening) and mod-MPI.

RESULTS

There was no statistically significant difference between the groups in terms of maternal age, BMI or gestational age at the time of examination (p > 0.05 for all). No statistically significant differences were found between the findings of conventional echocardiographic measurements and left ventricular mod-MPI between the study and control groups (p > 0.05 for all).

CONCLUSION

Fetal left ventricular mod-MPI is not affected by the presence of an IHF in the fetal left ventricle between 20th and 24th gestational weeks and thus it does not need to be assessed in this situation.

Optimal risk assessment of small-for-gestational-age fetuses using 31-34-week biometry in a low-risk population

OBJECTIVE

To compare the performance of traditional growth charts for estimated fetal weight (EFW) and a validated pragmatic probabilistic approach using biometry at 31-34 weeks' gestation to screen for late pregnancy small-for-gestational age (SGA) fetuses in a low-risk population.

METHODS

Records of ultrasound biometry at 31-34 weeks were reviewed in 7755 consecutive low-risk women between 2002 and 2011. Fetal malformations, Doppler anomalies and preterm delivery before 37 weeks were excluded. SGA was defined by various percentile cut-offs of birth weight. The probability of SGA was modeled as a function of Z-scores of femur length, abdominal circumference and head circumference. The model was validated on a second independent dataset of 1725 pregnancies from a different screening unit. The screening performance of this probabilistic approach was compared with those of traditional EFW growth charts. The additional value of factoring in maternal characteristics was also ascertained.

RESULTS

Using national birth-weight charts, the proportions of newborns at 37-42 weeks with birth weight<3(rd) , <5(th) and<10(th) centiles were 3%, 6% and 12%, respectively, and there was a 2% rate of birth weight<2500 g. For a 10% false-positive rate, a direct probabilistic approach yielded a 51% detection rate of neonates with birth weight<10(th) centile, compared to the 32% and 48% detection rates given by the 10(th) centile cut-off of two reference charts for EFW. Adding maternal characteristics significantly improved detection rate by 2% to 53%.

CONCLUSIONS

The suggested validated approach to screening for late SGA fetuses outperforms traditional approaches using growth charts. By adding maternal characteristics, this screening method offers a favorable alternative to customized charts.

Timing delivery of the growth-restricted fetus

Intrauterine growth restriction (IUGR) is commonly defined as an estimated fetal weight of less than the 10th percentile. While 70% of these are small for normal reasons and not at risk, 30% are pathologically small at risk for numerous complications including fetal death. In the late preterm IUGR fetus (>34 weeks), prematurity risks less and the risk of fetal demise becomes the primary concern. Pulsed-wave Doppler interrogation of the umbilical and middle cerebral artery is useful in reducing perinatal mortality, however, Doppler changes in these vessels of the IUGR fetus may not occur after 34 weeks gestation. There are no randomized trials addressing the timing of delivery of the IUGR fetus in the late preterm or early-term period. However, retrospective reports show an increase risk of fetal demise. While timing the delivery of the late preterm/early-term IUGR fetus requires consideration of multiple factors (e.g. degree of growth restriction, etiology, amniotic fluid volume, and biophysical and Doppler testing), available data suggests that delivery should occur by 37 to 38 weeks for singleton IUGR fetuses. In twin pregnancies with a co-twin IUGR fetus, chorionicity also impacts timing of delivery, but delivery should occur by 34-36 weeks.

[Is it necessary to induce labor before 37 weeks of gestation in case of small for gestational age fetus?]

The suspicion of small for gestational age fetus before 37 weeks of gestation implies to discriminate those who are physiologically small from those who have an underlying pathology leading to growth retardation. A labor induction can be needed if the risks associated to the prolongation of the pregnancy are estimated to be higher than those of prematurity and cesarean. In this case, labor induction can be discussed if the fetal vitality is normal. A continuous fetal heart monitoring during induction and labor is, in this case, strongly recommended. However, even in these optimal conditions, the risk of cesarean in case of labor induction for small for gestational age fetus before 37 weeks of gestation is of about 50 % in the rare published studies.