Changes with time in fetal heart rate variation, movement incidences and haemodynamics in intrauterine growth retarded fetuses: a longitudinal approach to the assessment of fetal well being

The role of the fetal biophysical profile in the management of fetal growth restriction

Growth-restricted fetuses are at risk of hypoxemia, acidemia, and stillbirth because of progressive placental dysfunction. Current fetal well-being, neonatal risks following delivery, and the anticipated rate of fetal deterioration are the major management considerations in fetal growth restriction. Surveillance has to quantify the fetal risks accurately to determine the delivery threshold and identify the testing frequency most likely to capture future deterioration and prevent stillbirth. From the second trimester onward, the biophysical profile score correlates over 90% with the current fetal pH, and a normal score predicts a pH >7.25 with a 100% positive predictive value; an abnormal score on the other hand predicts current fetal acidemia with similar certainty. Between 30% and 70% of growth-restricted fetuses with a nonreactive heart rate require biophysical profile scoring to verify fetal well-being, and an abnormal score in 8% to 27% identifies the need for delivery, which is not suspected by Doppler findings. Future fetal well-being is not predicted by the biophysical profile score, which emphasizes the importance of umbilical artery Doppler and amniotic fluid volume to determine surveillance frequency. Studies with integrated surveillance strategies that combine frequent heart rate monitoring with biophysical profile scoring and Doppler report better outcomes and stillbirth rates of between 0% and 4%, compared with those between 8% and 11% with empirically determined surveillance frequency. The variations in clinical behavior and management challenges across gestational age are better addressed when biophysical profile scoring is integrated into the surveillance of fetal growth restriction. This review aims to provide guidance on biophysical profile scoring in the in- and outpatient management of fetal growth restriction.

Clinical Opinion: The diagnosis and management of suspected fetal growth restriction: an evidence-based approach

This study reviewed the literature about the diagnosis, antepartum surveillance, and time of delivery of fetuses suspected to be small for gestational age or growth restricted. Several guidelines have been issued by major professional organizations, including the International Society of Ultrasound in Obstetrics and Gynecology and the Society for Maternal-Fetal Medicine. The differences in recommendations, in particular about Doppler velocimetry of the ductus venosus and middle cerebral artery, have created confusion among clinicians, and this review has intended to clarify and highlight the available evidence that is pertinent to clinical management. A fetus who is small for gestational age is frequently defined as one with an estimated fetal weight of <10th percentile. This condition has been considered syndromic and has been frequently attributed to fetal growth restriction, a constitutionally small fetus, congenital infections, chromosomal abnormalities, or genetic conditions. Small for gestational age is not synonymous with fetal growth restriction, which is defined by deceleration of fetal growth determined by a change in fetal growth velocity. An abnormal umbilical artery Doppler pulsatility index reflects an increased impedance to flow in the umbilical circulation and is considered to be an indicator of placental disease. The combined finding of an estimated fetal weight of <10th percentile and abnormal umbilical artery Doppler velocimetry has been widely accepted as indicative of fetal growth restriction. Clinical studies have shown that the gestational age at diagnosis can be used to subclassify suspected fetal growth restriction into early and late, depending on whether the condition is diagnosed before or after 32 weeks of gestation. The early type is associated with umbilical artery Doppler abnormalities, whereas the late type is often associated with a low pulsatility index in the middle cerebral artery. A large randomized clinical trial indicated that in the context of early suspected fetal growth restriction, the combination of computerized cardiotocography and fetal ductus venosus Doppler improves outcomes, such that 95% of surviving infants have a normal neurodevelopmental outcome at 2 years of age. A low middle cerebral artery pulsatility index is associated with an adverse perinatal outcome in late fetal growth restriction; however, there is no evidence supporting its use to determine the time of delivery. Nonetheless, an abnormality in middle cerebral artery Doppler could be valuable to increase the surveillance of the fetus at risk. We propose that fetal size, growth rate, uteroplacental Doppler indices, cardiotocography, and maternal conditions (ie, hypertension) according to gestational age are important factors in optimizing the outcome of suspected fetal growth restriction.

Longitudinal Course of Short-Term Variation and Doppler Parameters in Early Onset Growth Restricted Fetuses

PURPOSE

 To evaluate the longitudinal pattern of fetal heart rate short term variation (STV) and Doppler indices and their correlation to each other in severe growth restricted (IUGR) fetuses.

MATERIALS AND METHODS

 In this retrospective study, pregnancies with a birth weight below the 10th percentile, born between 24 and 34 gestational weeks with serial Doppler measurements in combination with a computerized CTG (cCTG) with calculated STV were included. Longitudinal changes of both Doppler indices and STV values were evaluated with generalized additive models, adjusted for gestational age and the individual. For all measurements the frequency of abnormal values with regard to the time interval before delivery and Pearson correlations between Doppler indices and STV values were calculated.

RESULTS

 41 fetuses with a total of 1413 observations were included. Over the course of the whole study period, regression analyses showed no significant change of STV values (p = 0.38). Only on the day of delivery, a prominent decrease was observed (mean STV d28-22: 7.97 vs. mean STV on day 0: 6.8). Doppler indices of UA and MCA showed a continuous, significant deterioration starting about three weeks prior to delivery (p = 0.007; UA and p < 0.001, MCA). Correlation between any Doppler index and STV values was poor.

CONCLUSION

 Fetal heart rate STV does not deteriorate continuously. Therefore, cCTG monitoring should be performed at least daily in these high-risk fetuses. Doppler indices of umbilical artery (UA) and middle cerebral artery (MCA), however, showed continuous deterioration starting about 3 weeks prior to delivery.

Understanding Fetal Heart Rate Patterns That May Predict Antenatal and Intrapartum Neural Injury

Electronic fetal heart rate (FHR) monitoring is widely used to assess fetal well-being throughout pregnancy and labor. Both antenatal and intrapartum FHR monitoring are associated with a high negative predictive value and a very poor positive predictive value. This in part reflects the physiological resilience of the healthy fetus and the remarkable effectiveness of fetal adaptations to even severe challenges. In this way, the majority of "abnormal" FHR patterns in fact reflect a fetus' appropriate adaptive responses to adverse in utero conditions. Understanding the physiology of these adaptations, how they are reflected in the FHR trace and in what conditions they can fail is therefore critical to appreciating both the potential uses and limitations of electronic FHR monitoring.

Longitudinal study of computerized cardiotocography in early fetal growth restriction

OBJECTIVES

To explore whether, in early fetal growth restriction (FGR), the longitudinal pattern of fetal heart rate (FHR) short-term variation (STV) can be used to identify imminent fetal distress and whether abnormalities of FHR recordings are associated with 2-year infant outcome.

METHODS

The original TRUFFLE study assessed whether, in early FGR, delivery based on ductus venosus (DV) Doppler pulsatility index (PI), in combination with safety-net criteria of very low STV on cardiotocography (CTG) and/or recurrent FHR decelerations, could improve 2-year infant survival without neurological impairment in comparison with delivery based on CTG monitoring only. This was a secondary analysis of women who delivered before 32 weeks and had consecutive STV data recorded > 3 days before delivery and known infant outcome at 2 years of age. Women who received corticosteroids within 3 days of delivery were excluded. Individual regression line algorithms of all STV values, except the last one before delivery, were calculated. Life tables and Cox regression analysis were used to calculate the daily risk for low STV or very low STV and/or FHR decelerations (below DV group safety-net criteria) and to assess which parameters were associated with this risk. Furthermore, it was assessed whether STV pattern, last STV value or recurrent FHR decelerations were associated with 2-year infant outcome.

RESULTS

One hundred and forty-nine women from the original TRUFFLE study met the inclusion criteria. Using the individual STV regression lines, prediction of a last STV below the cut-off used by the CTG monitoring group had sensitivity of 42% and specificity of 91%. For each day after study inclusion, the median risk for low STV (CTG group cut-off) was 4% (interquartile range (IQR), 2-7%) and for very low STV and/or recurrent FHR decelerations (below DV group safety-net criteria) was 5% (IQR, 4-7%). Measures of STV pattern, fetal Doppler (arterial or venous), birth-weight multiples of the median and gestational age did not usefully improve daily risk prediction. There was no association of STV regression coefficients, a low last STV and/or recurrent FHR decelerations with short- or long-term infant outcomes.

CONCLUSION

The TRUFFLE study showed that a strategy of DV monitoring with safety-net criteria of very low STV and/or recurrent FHR decelerations for delivery indication could increase 2-year infant survival without neurological impairment. This post-hoc analysis demonstrates that, in early FGR, the daily risk of abnormal CTG, as defined by the DV group safety-net criteria, is 5%, and that prediction is not possible. This supports the rationale for CTG monitoring more often than daily in these high-risk fetuses. Low STV and/or recurrent FHR decelerations were not associated with adverse infant outcome and it appears safe to delay intervention until such abnormalities occur, as long as DV-PI is within normal range. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Fetal movements as a predictor of health

The key determinant to a fetus maintaining its health is through adequate perfusion and oxygen transfer mediated by the functioning placenta. When this equilibrium is distorted, a number of physiological changes, including reduced fetal growth, occur to favor survival. Technologies have been developed to monitor these changes with a view to prolong intrauterine maturity while reducing the risks of stillbirth. Many of these strategies involve complex interpretation, for example Doppler ultrasound for fetal blood flow and computerized analysis of fetal heart rate changes. However, even with these modalities of fetal assessment to determine the optimal timing of delivery, fetal movements remain integral to clinical decision-making. In high-risk cohorts with fetal growth restriction, the manifestation of a reduction in perceived movements may warrant an expedited delivery. Despite this, there has been little evolution in the development of technologies to objectively evaluate fetal movement behavior for clinical application. This review explores the available literature on the value of fetal movement analysis as a method of assessing fetal wellbeing, and demonstrates how interdisciplinary developments in this area may aid in the improvement of clinical outcomes.

Respiratory sinus arrhythmia in growth restricted fetuses with normal Doppler hemodynamic indices

BACKGROUND

The autonomic behavior of growth-restricted fetuses at different evolving hemodynamic stages has not been fully elicited.

AIM

To analyze the respiratory sinus arrhythmia (RSA) of growth-restricted fetuses that despite this severe condition show normal Doppler hemodynamics.

SUBJECTS

10 growth-restricted fetuses (FGR group) with normal arterial pulsatility indices (umbilical, uterine, middle cerebral, ductus venosus and aortic isthmus), and 10 healthy fetuses (Control group), 32-37weeks of gestation.

METHOD

B-mode ultrasound images for visualizing fetal breathing movements (FBM) or breathing akinesis (FBA), and the simultaneous RR-interval time series from maternal abdominal ECG recordings were obtained. The root-mean-square of successive differences of RR-intervals (RMSSD) was considered as a RSA-related parameter among the instantaneous amplitude of the high-frequency component (AMPHF) and its corresponding instantaneous frequency (IFHF), both computed by using empirical mode decomposition. Mean fetal heart-periods and RSA-related parameters were assessed during episodes of FBM and FBA in 30s length windows.

RESULTS

FGR and Control groups presented RSA-related fluctuations during FBM and FBA. Also, both groups showed significant higher (p<0.001) values for the mean heart-period, RMSSD and AMPHF during FBM. No-significant differences (p>0.05) were found for the IFHF regardless of breathing activity (FBM vs. FBA).

CONCLUSION

Growth-restricted fetuses without evident hemodynamic compromise exhibit a preserved autonomic cardiovascular regulation, characterized by higher values of RSA and mean heart-period in the presence of FBM. This physiological response reflects a compensatory strategy that may contribute to preserve blood flow redistribution to vital organs.

Fractal Analysis and Hurst Parameter for Intrapartum Fetal Heart Rate Variability Analysis: A Versatile Alternative to Frequency Bands and LF/HF Ratio

Background

The fetal heart rate (FHR) is commonly monitored during labor to detect early fetal acidosis. FHR variability is traditionally investigated using Fourier transform, often with adult predefined frequency band powers and the corresponding LF/HF ratio. However, fetal conditions differ from adults and modify spectrum repartition along frequencies.

Aims

This study questions the arbitrariness definition and relevance of the frequency band splitting procedure, and thus of the calculation of the underlying LF/HF ratio, as efficient tools for characterizing intrapartum FHR variability.

Study Design

The last 30 minutes before delivery of the intrapartum FHR were analyzed.

Subjects

Case-control study. A total of 45 singletons divided into two groups based on umbilical cord arterial pH: the Index group with pH ≤ 7.05 (n = 15) and Control group with pH > 7.05 (n = 30).

Outcome Measures

Frequency band-based LF/HF ratio and Hurst parameter.

Results

This study shows that the intrapartum FHR is characterized by fractal temporal dynamics and promotes the Hurst parameter as a potential marker of fetal acidosis. This parameter preserves the intuition of a power frequency balance, while avoiding the frequency band splitting procedure and thus the arbitrary choice of a frequency separating bands. The study also shows that extending the frequency range covered by the adult-based bands to higher and lower frequencies permits the Hurst parameter to achieve better performance for identifying fetal acidosis.

Conclusions

The Hurst parameter provides a robust and versatile tool for quantifying FHR variability, yields better acidosis detection performance compared to the LF/HF ratio, and avoids arbitrariness in spectral band splitting and definitions.

Intrauterine growth restriction and cerebral palsy

Intrauterine growth restriction (IUGR) can be described as condition in which fetus fails to reach his potential growth. It is common diagnosis in obstetrics, and carries an increased risk of perinatal mortality and morbidity. Moreover, IUGR has lifelong implications on health, especially on neurological outcome. There is a need for additional neurological assessment during monitoring of fetal well-being, in order to better predict antenatally which fetuses are at risk for adverse neurological outcome. Studies have revealed that the behavior of the fetus reflects the maturational processes of the central nervous system (CNS). Hence, ultrasound investigation of the fetal behavior can give us insight into the integrity and functioning of the fetal CNS. Furthermore, investigations carried out using modern method, four-dimensional (4D) sonography, have produced invaluable details of fetal behavior and its development, opening the door to a better understanding of the prenatal functional development of the CNS. Based on previous observations and several years of investigation, our reaserch group has proposed a new scoring system for the assessment of fetal neurological status by 4D sonography named Kurjak antenatal neurodevelopmental test (KANET). The value of KANET in distinguishing fetal brain and neurodevelopmental alterations due to the early brain impairment in utero is yet to be assessed in large population studies. However, preliminary results are very encouraging.

Perinatal outcomes in twin pregnancies with discordant Doppler velocimetric findings

OBJECTIVES

The purpose of this study was to investigate whether poor perinatal outcomes are more common in twins with abnormal umbilical artery Doppler velocimetric findings than in their siblings with normal findings.

METHODS

A matched-pair cohort analysis of twin pregnancies with discordant umbilical artery Doppler velocimetric findings (one normal and one abnormal) was performed. Both severely abnormal findings (defined as absent or reversed flow in one twin; n = 23) and mildly abnormal findings (defined as an elevated systolic to diastolic ratio in one twin; n = 28) were included. The matched twins provided a gestational age-and demographically matched comparison group. Outcomes measured included intrauterine fetal death, oligohydramnios, intrauterine growth restriction, and neonatal outcomes (birth weight, Apgar scores, intraventricular hemorrhage, necrotizing enterocolitis, respiratory distress syndrome, bronchopulmonary dysplasia, and sepsis). Associations between abnormal Doppler velocimetric findings and perinatal outcomes were estimated using matched logistic regression analysis.

RESULTS

Among this cohort of twin pregnancies with discordant umbilical artery Doppler velocimetric findings, oligohydramnios and intrauterine growth restriction were more frequent in twin fetuses with abnormal findings. Adverse neonatal outcomes were high in both groups (57% among those with normal findings and 49% among those with abnormal findings) because of the overwhelming contribution of preterm delivery (mean gestational age at delivery, 33.3 weeks) but were not significantly different between those fetuses with abnormal findings compared to their cotwins with normal findings.

CONCLUSIONS

Our results do not show an association between abnormal umbilical artery Doppler velocimetric findings and short-term adverse neonatal outcomes.

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.

Neurodevelopment following fetal growth restriction and its relationship with antepartum parameters of placental dysfunction

Placental dysfunction leading to fetal growth restriction (FGR) is an important risk factor for neurodevelopmental delay. Recent observations clarify that FGR evolves prenatally from a preclinical phase of abnormal nutrient and endocrine milieu to a clinical phase that differs in characteristics in preterm and term pregnancies. Relating childhood neurodevelopment to these prenatal characteristics offers potential advantages in identifying mechanisms and timing of critical insults. Based on available studies, lagging head circumference, overall degree of FGR, gestational age, and umbilical artery (UA), aortic and cerebral Doppler parameters are the independent prenatal determinants of infant and childhood neurodevelopment. While head circumference is important independent of gestational age, overall growth delay has the greatest impact in early onset FGR. Gestational age has an overriding negative effect on neurodevelopment until 32-34 weeks' gestation. Accordingly, the importance of Doppler status is demonstrated from 27 weeks onward and is greatest when there is reversed end-diastolic velocity in the UA or aorta. While these findings predominate in early-onset FGR, cerebral vascular impedance changes become important in late onset FGR. Abnormal motor and neurological delay occur in preterm FGR, while cognitive effects and abnormalities that can be related to specific brain areas increase in frequency as gestation advances, suggesting different pathophysiology and evolving vulnerability of the fetal brain. Observational and management studies do not suggest that fetal deterioration has an independent impact on neurodevelopment in early-onset FGR. In late-onset FGR further research needs to establish benefits of perinatal intervention, as the pattern of vulnerability and effects of fetal deterioration appear to differ in the third trimester.

Changes in fetal motility as a result of congenital disorders: an overview

After 35 years of real-time two-dimensional sonography, can we now identify changes in fetal motility indicative of malfunction of the central nervous system in high-risk pregnancies? A literature search on motor assessment procedures (movements specified for body part (SMP), quantity, quality and behavioral state), and motor milestones obtained per fetus (with various congenital disorders) yielded 48 articles describing motility of 104 fetuses. In 67%, SMPs (especially isolated arm or leg movements, breathing and general movements) were assessed. Quantitative aspects were examined in 76%, qualitative aspects in 62% and behavioral states in two fetuses. Abnormal motility can be divided into two main subcategories: hypo- and hyperkinetic, demonstrating decreased variation in qualitative performance (reduced or increased, respectively, amplitude, speed and number of participating body parts, abnormal quantity (reduced or increased, respectively) and reduced differentiation into SMPs. Posture was affected in 40/60 hypokinetic and 4/44 hyperkinetic moving fetuses. The majority of the disorders resulted in an adverse outcome. Fourteen percent survived with a handicap, depending on the underlying disorder. The 16 disorders with hypokinetic motility had mainly an autosomal recessive etiology with no possibility of invasive prenatal diagnosis or conclusive sonographic structural anomalies, in contrast to the 17 disorders with hyperkinetic motility. Within the limitations of the studies, a deeper understanding of affected milestones in motor development can be obtained. Broadening motor assessment procedures from quantitative only to include qualitative aspects, differentiation of SMPs and behavioral states and emphasizing onset and continuity of motility before and after birth will enhance the reliability and predictive value of motility as a parameter in the assessment of fetal condition.

Auditory processing deficits in growth restricted fetuses affect later language development

An increased risk for language deficits in infants born growth restricted has been reported in follow-up studies for more than 20 years, suggesting a relation between fetal auditory system development and later language learning. Work with animal models indicate that there are at least two ways in which growth restriction could affect the development of auditory perception in human fetuses: a delay in myelination or conduction and an increase in sensorineural threshold. Systematic study of auditory function in growth restricted human fetuses has not been reported. However, results of studies employing low-risk fetuses delivering as healthy full-term infants demonstrate that, by late gestation, the fetus can hear, sound properties modulate behavior, and sensory information is available from both inside (e.g., maternal vascular) and outside (e.g., noise, voices, music) of the maternal body. These data provide substantive evidence that the auditory system is functioning and that environmental sounds are available for shaping neural networks and laying the foundation for language acquisition before birth. We hypothesize that fetal growth restriction affects auditory system development, resulting in atypical auditory information processing in growth restricted fetuses compared to healthy, appropriately-grown-for-gestational-age fetuses. Speech perception that lays the foundation for later language competence will differ in growth restricted compared to normally grown fetuses and be associated with later language abilities.

The computerized fetal heart rate analysis in post-term pregnancy identifies patients at risk for fetal distress in labour

OBJECTIVE

To ascertain the diagnostic ability of a computerized fetal heart rate (FHR) analysis system in the identification of patients at risk of fetal distress in labour.

STUDY DESIGN

Three hundred and two healthy post-term pregnancies were enrolled in a retrospective, cross-sectional study and subdivided into two groups, with (n=42) or without (n=260) fetal distress in labour. The last computerized FHR recording before onset of labour was analyzed.

RESULTS

The two groups showed a significant difference only in FHR baseline and in percentage of small accelerations on total. The multivariate analysis showed that only the percentage of small accelerations was significantly related to the labour outcome. A higher diagnostic accuracy was obtained with use of neural network analysis, which allowed a sensitivity of 56%, specificity 91%, positive predictive value 53% and negative predictive value 92% with an overall accuracy of 86%.

CONCLUSIONS

The increase in FHR baseline and in small FHR accelerations can be major factors in the prediction of subsequent fetal distress in healthy term fetuses. Use of neural networks seems to further improve the ability of computerized FHR analysis in the prediction of intrapartum distress.

Doppler and biophysical assessment in growth restricted fetuses: distribution of test results

OBJECTIVE

Multi-vessel Doppler ultrasonography and biophysical profile scoring (BPS) are used in the surveillance of growth restricted fetuses (IUGR). The interpretation of both tests performed concurrently may be complex. This study examines the relationship between Doppler ultrasonography and biophysical test results in IUGR fetuses.

METHODS

Three hundred and twenty-eight IUGR fetuses (abdominal circumference < 5th percentile, elevated umbilical artery (UA) pulsatility index (PI)) had concurrent surveillance with UA, middle cerebral artery (MCA) and ductus venosus (DV) Doppler ultrasonography and BPS (fetal tone, movement, breathing, maximal amniotic fluid pocket and fetal heart rate). Patients were stratified into three groups according to their Doppler examination: (1) abnormal UA alone; (2) brain sparing (MCA-PI > 2 SD below mean for gestational age); and (3) abnormal DV (PI > 2 SD above the mean for gestational age) and BPS groups: (1) normal (> 6/10); (2) equivocal (6/10); and (3) abnormal (< 6/10). Predictions of short-term perinatal outcomes by both modalities were compared for stratification. The distribution and concordance of Doppler and BPS test results were examined for the whole patient group and based on delivery prior to 32 weeks' gestation.

RESULTS

Abnormal UA Doppler results alone were observed in 109 fetuses (33.2%), brain sparing in 87 (26.5%) and an abnormal DV in 132 (40.2%). The BPS was normal in 158 (48.2%), equivocal in 68 (20.7%) and abnormal in 102 (31.1%). Both testing modalities stratified patients into groups with comparable acid-base disturbance and perinatal outcome. Of the nine possible test combinations the largest subgroups were: abnormal UA alone/normal BPS (n = 69; 21%) and abnormal DV Doppler/abnormal BPS (n = 62; 18.9%). Assessment of compromise by both testing modalities was concordant in 146 (44.5%) cases. In 182 fetuses with discordant results the BPS grade was better in 115 (63.2%, P < 0.0001). Marked disagreement of test abnormality was present in 57 (17.4%) fetuses. Of these, abnormal venous Doppler in the presence of a normal BPS constituted the largest group (Chi-square P < 0.002). Stratification was not significantly different in patients delivered prior to 32 weeks' gestation.

CONCLUSION

Doppler ultrasonography and BPS effectively stratify IUGR fetuses into risk categories, but Doppler and BPS results do not show a consistent relationship with each other. Since fetal deterioration appears to be independently reflected in these two testing modalities further research is warranted to investigate how they are best combined.

The relationship between an aortic isthmus blood flow velocity index and the postnatal neurodevelopmental status of fetuses with placental circulatory insufficiency

OBJECTIVE

The purpose of this study was to evaluate the association between an abnormal aortic isthmus blood flow index and postnatal neurodevelopmental outcome in fetuses with placental circulatory insufficiency. STUDY DESIGN Forty-eight children who were born between 1991 and 1999 were included in this study on the basis of abnormal umbilical artery Doppler velocimetry. Prenatal isthmus blood flow index was obtained by dividing the sum of the systolic and diastolic Doppler blood flow velocity integrals by the systolic blood flow integrals. Neurodevelopmental outcome between 2 and 5 years was classified as optimal, when neurologic assessment and developmental quotient were within normal limits and as nonoptimal when abnormal neurologic findings and/or a nonoptimal developmental quotient was present. Neurodevelopmental outcome was analyzed in relation to isthmus flow index and pulsatility indices in the umbilical artery.

RESULTS

The mean gestational age at delivery was 33.0 +/- 2 weeks. Nonoptimal neurodevelopmental outcome was found in 60.4% of the children (29/48). An inverse correlation was found between the isthmus blood flow index and postnatal neurodevelopmental outcome. All 13 children with an isthmus blood flow index of <0.5 were in the nonoptimal group. All 19 children with an optimal outcome had an isthmus blood flow index of >0.5, but this was also the case for 16 other children with nonoptimal neurodevelopmental outcome. An isthmus blood flow index cut-off value of 0.70 was associated with the highest overall positive and negative predictive values. The pulsatility index in the umbilical artery did not provide any significant contribution in the explanation of the outcome.

CONCLUSION

The isthmic blood flow index can help to identify a subgroup of fetuses with placental circulatory insufficiency that might benefit from early delivery.

Pathophysiology of Fetal Growth Restriction: Implications for Diagnosis and Surveillance

Normal fetal growth depends on the genetically predetermined growth potential and is modulated by fetal, placental, maternal, and external factors. Fetuses with intrauterine growth restriction (IUGR) are at high risk for poor short- and long-term outcome. Although there are many underlying etiologies, IUGR resulting from placental insufficiency is most relevant clinically because outcome could be altered by appropriate diagnosis and timely delivery. A diagnostic approach that aims to separate IUGR resulting from placental disease from constitutionally small fetuses and those with other underlying etiologies (e.g., aneuploidy, viral infection, nonaneuploid syndromes) needs to integrate multiple imaging modalities. In placental-based IUGR, cardiovascular and behavioral responses are interrelated with the disease severity. Ultrasound assessment of fetal anatomy, amniotic fluid volume, and growth is complementary to the Doppler investigation of fetoplacental blood flow dynamics. A diagnostic approach to IUGR combining these modalities is presented in this review.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians.

LEARNING OBJECTIVES

After completion of this article, the reader should be able to describe the development of the placental interface, to outline the mechanisms of placental insufficiency, and to list the manifestations of placental insufficiency and the tests that can be used to diagnose fetal growth restriction.

Fetal growth restriction due to placental disease

Normal fetal growth depends on the genetically predetermined growth potential and its modulation by the health of the fetus, placenta and the mother. Fetuses that are small because of intrauterine growth restriction (IUGR) are at higher risk for poor perinatal and long-term outcome than those who are appropriately grown. Of the many potential underlying processes that may result in IUGR, placental disease is clinically the most relevant. Fetal cardiovascular and behavioral responses to placental insufficiency and the metabolic status are interrelated. The concurrent evaluation of fetal biometry, amniotic fluid volume, heart rate patterns, arterial and venous Doppler, and biophysical variables therefore allow the most comprehensive fetal evaluation in IUGR. In the absence of successful intrauterine therapy, the timing of delivery is perhaps the most critical aspect of the antenatal management. A discussion of the fetal responses to placental insufficiency and a management protocol that accounts for multiple Doppler and biophysical parameters as well as gestational age is provided in this review.

Fetal heart rate in relation to its variation in normal and growth retarded fetuses

OBJECTIVES

(1) to assess the relationship of basal fetal heart rate (FHR) with both long term (LTV) and short term (STV) FHR variation in low-risk pregnancies, longitudinally from 24 weeks gestation onwards and (2) to investigate the relationship of FHR with LTV and STV in intrauterine growth retarded (IUGR) fetuses.

STUDY DESIGN

Computerised FHR recordings were made in twenty-nine uncomplicated pregnancies (n=224) and in twenty-seven IUGR fetuses who were selected retrospectively from three databases (n=135). Nomograms of FHR variation with FHR and GA were constructed using multilevel analysis.

RESULTS AND CONCLUSIONS

There was a strong negative relationship of FHR with both LTV and STV in the control group (R2=53% and 52%, respectively). In the IUGR fetuses, FHR was generally higher than in normal fetuses whereas LTV and STV were lower. The relationship of FHR with LTV and STV in the IUGR group was less strong (for both: R2=18%). Correction of FHR variation for basal FHR in the IUGR fetuses only resulted in a slight reduction in the number of recordings with a variation below the normal range. As it does not improve the recognition of fetuses being considered at the highest risk, such a correction of FHR variation for basal FHR is therefore not necessary. Intrafetal consistency, known to be present in healthy fetuses, was also present in the IUGR fetuses with a low FHR variation.

Computerised analysis of behaviour in normal and growth-retarded fetuses

Fetal behaviour [fetal heart rate (FHR) variation and movements (FA)] was studied in 27 normally grown fetuses and in 18 fetuses with intrauterine growth restriction (IUGR). FHR and FA were recorded using a single 1.5 MHz ultrasound transducer and analyzed by computer. The IUGR fetuses had significantly lower FA rates than the normally grown fetuses at all gestation times. They also spent a significantly lower proportion of time exhibiting high FHR variation at 28-31 weeks. Only two of the eighteen IUGR fetuses had abnormal biophysical profile scores (BPS) at the time of recording and yet all but one of them had either FHR or FA patterns that were outside the 10-90th centile range for the normally grown fetuses, suggesting that FHR and FA abnormalities predated BPS changes. More of the IUGR fetuses had abnormalities of FA than FHR. Finally, within the IUGR fetuses, those with small head circumferences (less than 3rd centile) had lower FA rates during periods of both low and high FHR variation, though this was only statistically significant for periods of low FHR variation (P < 0.05). This preliminary study offers the possibility that such objective evaluation of fetal behaviour could be used in a clinical setting and provide a more sensitive method of fetal assessment than the BPS.

Spontaneous motility in preterm, small-for-gestational age infants. I. Quantitative aspects

The developmental course of the quantitative aspects of early spontaneous motility was studied longitudinally in fourteen intrauterine growth-retarded infants, with a birth weight below the 5th percentile, in relation to perinatal variables, brain ultrasound findings and neurological outcome. Quantitative motility was studied during the preterm period until term age, from 1 h videotape recordings, using Prechtl's classification of different spontaneous movement patterns. Comparison to a low-risk reference group, consisting of preterm, appropriate-for-gestational age infants, showed that significant differences were inconsistent and obviously by chance, with the possible exception of a decreased rate of startles from the 2nd to the 6th postnatal weeks. A trend of increasing duration of GMs was present with increasing postnatal age. There were hardly any correlations between perinatal variables and quantitative motility, and if present the correlations were weak. Such correlations were found between the reduction of heart-rate variability on cardiotocography and the rate of startles and twitches during the first week and furthermore between the neonatal blood glucose level and the rate of isolated arm movements and total motility during the first week. This study demonstrates that intrauterine growth retardation has little or no influence on the quantitative aspects of spontaneous motility postnatally during the preterm period.

Role of antepartum computerized fetal heart rate analysis in the prediction of fetal distress during labor

OBJECTIVE

To ascertain the diagnostic ability of a computerized fetal heart rate (FHR) analysis system in the identification of patients at risk of fetal distress in labor.

STUDY DESIGN

Five-hundred and seventy-seven healthy term pregnancies were enrolled in a prospective, cross-sectional study and subdivided into two groups, with (n = 90) or without (n = 487) fetal distress in labor. Computerized FHR recordings were performed periodically and regression analysis was performed in a univariate and multivariate way to assess the ability of the last FHR recordings in the prediction of subsequent fetal distress.

RESULTS

The two groups showed a significant difference in almost all of the FHR parameters studied. The multivariate analysis showed that only the FHR baseline and the percentage of small acceleration were independently and significantly related to the labor outcome. The combination of these two parameters reaches a sensitivity of 45%, specificity of 91%, positive predictive value of 48% and negative predictive value of 90%, with an overall accuracy of 84%.

CONCLUSIONS

The increase in FHR baseline and in small FHR accelerations can be major factors in the prediction of subsequent fetal distress in healthy term fetuses.

Prediction of fetal acidaemia in intrauterine growth retardation: comparison of quantified fetal activity with biophysical profile score

OBJECTIVE

To study the relation between quantified fetal movements and fetal activity assessed by the biophysical profile score and the pH in umbilical arterial blood at elective caesarean section.

DESIGN

Fetal activity was assessed within 24 h prior to caesarean section for decelerative fetal heart rate patterns both by quantification (% of time spent moving) and by applying the biophysical profile score (BPS) criteria.

SETTING

Department of Obstetrics, University Hospital.

SUBJECTS

Nineteen growth retarded fetuses.

MAIN OUTCOME MEASURES

Fetal generalised movements (FGM%), fetal breathing movements (FBM%), total fetal activity (TFA% = FGM% + FBM%); FGM, FBM and tone as assessed according the biophysical profile score (BPS); umbilical arterial pH.

RESULTS

In all 11 acidaemic fetuses (pH < 7.20) TFA% was below the 10th centile for normal fetuses; nine had decreased FGM% and eight decreased FBM%. Absence of FGM or tone according to the biophysical profile score was only seen in two acidaemic fetuses.

CONCLUSION

TFA% < 11.7% was a better predictor of acidaemia at birth than either reduced FGM%, FBM%, or absence of FGM, FBM and tone as defined in the biophysical profile score. The two methods of assessing FBM were identical in predicting acidaemia, suggesting that in presence of acidaemia the decrease of FBM may be an all-or-none phenomenon. Furthermore, the data indicate that reduction in body movements may precede reduction in breathing movements.