A critical appraisal of the use of umbilical artery Doppler ultrasound in high-risk pregnancies: use of meta-analyses in evidence-based obstetrics

Fetal and umbilical Doppler ultrasound in high-risk pregnancies

BACKGROUND

Abnormal blood flow patterns in fetal circulation detected by Doppler ultrasound may indicate poor fetal prognosis. It is also possible false positive Doppler ultrasound findings could encourage inappropriate early delivery.

OBJECTIVES

The objective of this review was to assess the effects of Doppler ultrasound used to assess fetal well-being in high-risk pregnancies on obstetric care and fetal outcomes.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (September 2009) and the reference lists of identified studies.

SELECTION CRITERIA

Randomised and quasi-randomised controlled trials of Doppler ultrasound for the investigation of umbilical and fetal vessels waveforms in high-risk pregnancies compared to no Doppler ultrasound.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed the studies for inclusion, assessed risk of bias and carried out data extraction. Data entry was checked.

MAIN RESULTS

Eighteen completed studies involving just over 10,000 women were included. The trials were generally of unclear quality with some evidence of possible publication bias. The use of Doppler ultrasound in high-risk pregnancy was associated a reduction in perinatal deaths (risk ratio (RR) 0.71, 95% confidence interval (CI) 0.52 to 0.98, 16 studies, 10,225 babies, 1.2% versus 1.7 %, numbers needed to treat = 203; 95%CI 103 to 4352). There were also fewer inductions of labour (average RR 0.89, 95% CI 0.80 to 0.99, 10 studies, 5633 women, random effects) and fewer caesarean sections (RR 0.90, 95% CI 0.84 to 0.97, 14 studies, 7918 women). No difference was found in operative vaginal births (RR 0.95, 95% CI 0.80 to 1.14, four studies, 2813 women) nor in Apgar scores less than seven at five minutes (RR 0.92, 95% CI 0.69 to 1.24, seven studies, 6321 babies).

AUTHORS' CONCLUSIONS

Current evidence suggests that the use of Doppler ultrasound in high-risk pregnancies reduced the risk of perinatal deaths and resulted in less obstetric interventions. The quality of the current evidence was not of high quality, therefore, the results should be interpreted with some caution. Studies of high quality with follow-up studies on neurological development are needed.

Obstetric management of intrauterine growth restriction

The aim of obstetric management is to identify growth-restricted foetuses at risk of severe intrauterine hypoxia, to monitor their health and to deliver when the adverse outcome is imminent. After 30-32 gestational weeks, a Doppler finding of absent or reverse end-diastolic flow in the umbilical artery of a small-for-gestational age foetus is in itself an indication for delivery. In very preterm foetuses, the intrauterine risks have to be balanced against the risk of prematurity. All available diagnostic information (e.g., Doppler velocimetry of umbilical artery, foetal central arteries and veins and of maternal uterine arteries; foetal heart rate with computerised analysis of short-term variability; amniotic fluid amount; and foetal gestational age-related weight) should be collected to support the timing of delivery. If possible, the delivery should optimally take place before the onset of late signs of foetal hypoxia (pathological foetal heart rate pattern, severely abnormal ductus venosus blood velocity waveform, pulsations in the umbilical vein).

Evaluation of the use of umbilical artery Doppler flow studies and outcome of pregnancies at a secondary hospital

OBJECTIVE

To investigate the use of a personal computer (PC)-based, continuous-wave Doppler machine by a trained midwife at a secondary hospital to assess umbilical artery flow velocity waveforms (FVW) in referred women.

METHODS

Pregnant women referred for suspected poor fetal growth were evaluated from June 2002 through December 2004. The Umbiflow apparatus, consisting of a Pentium 3 PC with an ultrasound transducer plugged into the USB port and software, was used to analyze the FVW of the umbilical artery. Pregnancies in which the resistance index (RI) was <75(th) percentile (P75) were not further evaluated for fetal well-being unless the clinical condition of the mother changed. Pregnancies with an RI >or=P75 were followed up according to a specific protocol. Primary end points were intrauterine death and intrauterine growth restriction.

RESULTS

A total of 572 singleton pregnancies were followed up. Significantly more infants were small-for-gestational-age when the RI was >P95 (55.6%) than those between P75 and P95 (41.2%) or <P75 (27.2%). Perinatal mortality rates were 13.2, 39.1 and 41.7 for women with RIs <P75, P75-95 and >P95, respectively.

CONCLUSIONS

A normal Doppler FVW of the umbilical artery is less likely to be followed by perinatal death.

Implementation of new medical techniques: Experience from the Swedish randomized controlled trial on fetal ECG during labor

BACKGROUND

In a large Swedish multicenter randomized controlled trial (RCT) on intra partum fetal monitoring with automatic analysis of fetal ECG waveform (STAN) in combination with cardiotocography (CTG) (4966 parturients, 300 obstetricians and midwives managing the patients), interim analysis revealed protocol violations. By a post hoc analysis of the results over time, factors affecting the acceptance of the new technique were analyzed.

METHODS

The rates of primary and secondary outcome measures (fetal outcome, operative deliveries) were compared in the two study groups (CTG + ST and CTG only). Changes over time were statistically evaluated using a test for homogeneity between the two periods.

RESULTS

After retraining, the CTG + ST group showed the lowest rates of operative delivery for fetal distress, fetal blood sampling and admissions to neonatal intensive care unit. Operative deliveries (p = 0.02) and the number of fetal blood sampling decreased significantly over time (p = 0.001).

CONCLUSIONS

Training and education probably predisposed the clinicians to a change and reinforced it when it occurred as a result of increased personal experience. The audit and feedback together with the influence of opinion leaders and inter-collegial interactions seem to have been of importance for the successively increasing acceptance of the new method during the RCT.

Fetal Doppler: umbilical artery, middle cerebral artery, and venous system

One of the most important applications of Doppler ultrasonography in obstetrics is the detection of fetal anemia in pregnancies complicated by either red-cell alloimmunization or by other causes of fetal anemia. Doppler of the umbilical artery also has prognostic value in pregnancies affected by twin-twin transfusion syndrome undergoing in-utero intervention. Another potential major application is the use of Doppler ultrasound in the management of intrauterine-growth-restricted fetuses. At the present time, there is no single test that appears superior to the other available tests for timing the delivery of the growth-restricted fetus. Therefore, the decision to deliver a fetus, especially at <32 weeks, remains mostly based on empirical management. Doppler may provide a more reliable and systematic basis for timing these deliveries. This review emphasizes the three following concepts: (a) normal and abnormal Doppler of the umbilical artery, middle cerebral artery, mitral and tricuspid valves, umbilical vein, and ductus venosus; (b) some clinical applications of Doppler sonography in obstetrics; and (c) potential future research of Doppler in obstetrics.

Pathological prenatal Doppler sonography findings and their association with neonatal cranial ultrasound abnormalities in a high risk collective

The aim of this study was to evaluate whether prenatal Doppler ultrasound plays a role in the risk assessment of neonatal abnormal cranial ultrasound findings (NACU). Doppler examinations of blood flow velocities in the umbilical artery (n = 132), the fetal middle cerebral artery (n = 96) and the ductus venosus (n = 46) were conducted in 132 consecutive high-risk cases. The cases were divided into three groups: normal (I), pathological (II) and highly pathological Doppler (III) results, according to the resistance index calculated and were assessed for any association between the Doppler groups and the short-term outcome of the neonate, especially NACU. A significant association was found between Doppler groups and gestational age at delivery, birth weight, length and head circumference, growth restriction, cesarean section rate, Apgar score and pH values. NACU was diagnosed significantly more often in the pathological (12.1%) and highly pathological (38.5%) Doppler groups than in the group with normal Doppler (1.7%; p < 0.001). Multivariate analysis showed that the Doppler groups (odds ratio 1.67, 95% confidence interval [CI] 1.14-2.84, p < 0.001) and gestational age at delivery (odds ratio 1.37, 95% CI 1.08-2.74; p < 0.001) were independent variables that could be used to predict NACU. The present study showed that a pathological prenatal Doppler result is highly predictive for NACU in addition to gestational age and can therefore be used for risk assessment.

Nontraditional sonographic pearls in estimating gestational age

Accurate gestational dating is one of the most important assessments obstetrical providers make in pregnancy, given that all of the various management strategies are dependent on knowing where the patient is in gestation. In addition to traditional biometry, ancillary biometric and nonbiometric measurements can help narrow the biologic variability between fetuses. Moreover, one can employ these nontraditional measurements both in late gestation to assist in determining appropriate gestational age and fetal lung maturity, and in other specific clinical situations-such as oligohydramnios, in which compression of the fetal head and abdomen can lead to difficulty in obtaining an accurate biparietal diameter and abdominal circumference. This chapter focuses on nontraditional fetal ultrasound measurements, including the transverse cerebellar diameter, fetal foot length, ratios of biometric and nonbiometric measurements, epiphyseal ossification centers, amniotic fluid volume, placental grading, and other miscellaneous markers in the context of evaluating a fetus with possible intrauterine growth restriction.

Doppler indices in the umbilical arteries: influence of vessel curvature induced by bladder filling

Doppler indices are widely used to assess normal versus pathologic haemodynamics. In obstetrics, the assessment of abnormal values in some critical compartments, such as the umbilical arteries (UA), may be crucial in the clinical management of growth-restricted foetuses. It was recently proposed that the UA should be sampled in their perivesical portion (PVC), i.e., where they surround the foetal urinary bladder. However, measurements at this site could be biased by the degree of curvature of the vessel due to bladder filling. We investigated this possibility in vivo and in vitro, i.e., measurements on rubber tubes at different radii of curvature R(c). There was significant dependence of the Doppler indices A/B and PI on the vessel curvature and insonation angle; in fact, we recorded errors of about 25% when R(c) was 10 times larger than the radius of the vessel and about 100% when R(c) was five times larger than the radius of the vessel. Therefore, measurements of the UA at the PVC site should only be performed when the foetal bladder is empty.

[Current recommendations for the treatment of preeclampsia]

Low-dose aspirin, but not vitamin C and vitamin E, has small to moderate benefits when used for the prevention of preeclampsia. There is however little to suggest that the course of manifest preeclampsia can be substantially affected by drug treatment. Antihypertensive therapy increases the risk of fetal growth restriction and is only indicated in severe hypertension to reduce the risk of maternal cerebral hemorrhage. Magnesium sulfate is the drug of choice for the prevention and treatment of eclampsia. Volume expansion as well as the use of steroids in preeclamptic patients without HELLP syndrome have failed to show any improvement. Delivery as the only definitive treatment is always beneficial for the mother whereas expectant management is in favor of a premature fetus. Decision-making largely depends on gestational age and severity of the disease.

Hemodynamic changes in the fetal arteries during the second half of pregnancy assessed by Doppler velocimetry

The applicability of Doppler velocimetry has been well established regarding intrauterine growth restriction and fetal hypoxia. This method can also be used to determine fetal anemia and cardiac malformations. The main fetal arteries evaluated by Doppler velocimetry are the middle cerebral artery and the umbilical artery. However, the fetal aorta is responsible for the distribution of blood flow to the upper and lower extremities of the human body and should also be properly valued. In order to characterize abnormalities in the arteries of high-risk fetuses, it is necessary to know the hemodynamic modifications of normal fetuses. On this basis, the authors performed a review of fetal hemodynamics evaluated by Doppler velocimetry in the fetal aorta and middle cerebral and umbilical arteries during the second half of pregnancy. The study of fetal vessels by Doppler velocimetry indirectly evaluates the hemodynamic changes occurring in fetuses at risk. In this respect, we emphasize the changes in Doppler velocimetry occurring in fetal anemia, in restricted intrauterine growth, and in normal fetuses.

A population-based study of 518 very preterm neonates from high-risk pregnancies: Prognostic value of umbilical and cerebral artery Doppler velocimetry for mortality before discharge and severe neurological morbidity

OBJECTIVE

To evaluate in everyday practice the predictiveness of fetal umbilical artery and cerebral artery Doppler examination for mortality before discharge and for severe neurological morbidity among very preterm neonates from high-risk pregnancies.

METHODS

Data came from a population-based study (EPIPAGE) of all births before 33 weeks' gestation during 1 year in nine French regions. We examined the prognostic value of Doppler findings among the liveborn singletons delivered after pregnancies with maternal hypertension or antenatal suspicion of small-for-gestational-age status.

RESULTS

This study included 518 fetuses. Predischarge mortality for infants with abnormal umbilical artery Doppler findings was not significantly higher than for those with normal findings. Mortality for infants with abnormal cerebral artery Doppler findings was significantly higher in the bivariate analysis (crude OR: 3.5 (1.6-7.4)). After adjustment, the association between mortality and abnormal cerebral artery Doppler findings remained significant in the subgroup with an abnormal umbilical artery Doppler assessment (OR: 5.1 (1.1-23)). There was no significant association between neurological morbidity and Doppler findings.

CONCLUSION

The prognostic value of Doppler examinations appears lower in this study than in previous hospital series. This suggests the need for quality control and improvements in these examinations.

Management of Fetal Growth Restriction: An Evidence-Based Approach

This review provides an evidence-based approach to the management of fetal growth restriction (FGR). The management consists of the following components: appropriate fetal surveillance, timely intervention, and selective etiological management. Umbilical arterial (UA) Doppler sonography is the primary test. Supplementary tests include nonstress test (NST), amniotic fluid assessment, biophysical profile (BPP), and selective venous Doppler sonography. Ominous signs include UA absent or reverse end-diastolic flow, non-assuring NST, low BPP, and abnormal fetal venous flow patterns. An evidence-based clinical management guideline is included and individualization of care is recommended.

Arterial and venous Doppler in the diagnosis and management of early onset fetal growth restriction

Key issues in the management of early onset fetal growth restriction (IUGR<34 weeks) are accurate diagnosis and assessment of fetal well-being to optimize timing of delivery by weighing fetal vs. neonatal risks. Cardiovascular, behavioral and fetal heart rate patterns in IUGR follow a predictable progression that corresponds with the severity of compromise. Umbilical artery (UA) Doppler primarily serves as a placental function test providing insufficient information to solely direct perinatal management. Venosus Doppler is an independent predictor of stillbirth and acidemia and needs to be examined when the UA index is elevated, especially if end-diastolic velocities are absent. Neonatal outcomes are primarily determined by gestational age and their antenatal prediction is too ineffective to guide management. Abnormal venous Doppler, biophysical profile score and mean minute variation of the fetal heart rate are strong predictors of fetal compromise therefore favoring delivery. Randomized trials indicate that delayed delivery has little effects on short-term outcome while producing a trend towards improved early childhood neurodevelopment. This stresses the need for excellent fetal surveillance techniques and their ongoing investigation through randomized management trials.

Increased latency of absent end-diastolic flow in the umbilical artery of monochorionic twin fetuses

OBJECTIVE

To determine if absent end-diastolic flow (AEDF) in the umbilical artery (UA) has a longer latency in monochorionic (MC) twin fetuses compared to singleton or dichorionic twin (DC) fetuses.

METHODS

One hundred and eight pregnancies with a fetus with AEDF were reviewed: 47 MC and 17 DC twin pregnancies and 44 singletons. Because twin-twin transfusion syndrome (TTTS) is a potential confounder when determining latency, subgroup analysis was also performed on the 21 MC affected pregnancies without TTTS. Latency of AEDF (in days) was defined as the difference between the gestational age at diagnosis of AEDF and gestational age at delivery or intrauterine death.

RESULTS

Latency was similar in MC twins (median, 39 days) and DC twins (30 days) but longer compared to singletons (11 days; P = 0.0001). After excluding pregnancies with TTTS, latency in non-TTTS MC twins (54 days) was longer than in both singletons and DC twins. This was due to an earlier gestational age at AEDF in non-TTTS MC twins of 20 weeks compared to 27 weeks in both singleton and DC twins because median gestational age at delivery was similar in MC twins, DC twins and singletons.

CONCLUSIONS

The latency period of UA AEDF is longer in MC twins than in singletons. Our data suggest that in MC twin fetuses without TTTS, AEDF begins earlier and lasts about twice as long as in DC twin fetuses, which is consistent with placental insufficiency not being the sole factor mediating abnormal UA waveforms in MC placentation. This observation is important in counseling and managing twin pregnancies discordant for AEDF.

Surveillance in longitudinal models: detection of intrauterine growth restriction

A new methodology for online detection of intrauterine growth restriction (IUGR) is proposed where traditional methods for statistical surveillance are applied. Here, deficient growth rate is used to detect IUGR instead of the common surrogate measure "small for gestational age" (SGA). Fetal growth is estimated by repeated measurements of symphysis-fundus (SF) height. At each time point the new method, based on the Shiryaev-Roberts method, is used to evaluate the growth in SF height. We use Swedish data to model a normal growth pattern, which is used to evaluate the capability of the new method to detect IUGR in comparison with a method used in practice today. Results from simulations indicate that the new method performs considerably better than the method used today. We also illustrate the effect of some important factors which influence the detection ability and illuminate the tendency of the method used today to misclassify SGA cases as IUGR.

Qualitative venous Doppler flow waveform analysis in preterm intrauterine growth-restricted fetuses with ARED flow in the umbilical artery--correlation with short-term outcome

OBJECTIVE

The aim of this retrospective study was to examine the significance of severe Doppler waveform abnormalities in the ductus venosus (DV) and the umbilical vein (UV) for the prediction of adverse outcomes in very preterm growth-restricted fetuses with absent or reversed end-diastolic flow in the umbilical artery (UA) at 24-34 weeks of gestation.

METHODS

Seventy-four fetuses with intrauterine growth restriction (IUGR) and absent or reversed end-diastolic (ARED) flow in the UA at 24-34 weeks of gestation, which were delivered before 34 weeks' gestation, were examined. Absent or reversed flow during atrial contraction (a-wave) in the DV and pulsatile flow in the UV were examined to predict severe perinatal outcomes (stillbirth, neonatal death, perinatal death, acidemia, 5 min Apgar < 7, intraventricular hemorrhage and elevated nucleated red blood cell counts at delivery).

RESULTS

Twelve (16.2%) perinatal deaths, of which eight were stillbirths (10.8%), and two (2.7%) neonatal deaths occurred among 74 fetuses. Logistic regression analysis confirmed that abnormal DV Doppler waveforms (R2 = 0.57, P < 0.001) together with gestational age at delivery (R2 = 0.57, P < 0.001) showed the strongest association with perinatal death, whereas only gestational age was significantly related to neonatal death (R2 = 0.67, P < 0.05). Abnormal DV Doppler waveforms (R2 = 0.86, P < 0.001) and gestational age (R2 = 0.49, P < 0.05) were strongly associated with adverse outcome (including stillbirth, perinatal death or neonatal death). Abnormal venous Doppler flow patterns performed better in the prediction of fetal or perinatal demise than did ARED flow or brain sparing.

CONCLUSION

Abnormal venous Doppler waveforms in preterm IUGR fetuses with ARED flow are strongly related to adverse fetal and perinatal outcomes before 32 weeks of gestation. The possible benefit of prolonging these pregnancies can only be evaluated in a prospective randomized study.

Use of umbilical-cerebral Doppler ratios in predicting fetal growth restriction in near-term fetuses

OBJECTIVE

To compare the sensitivity and specificity of different umbilical-cerebral ratios in the prediction and detection of fetal growth restriction in near-term fetuses when the umbilical arterial waveform is within normal.

METHODS

A prospective cross-sectional observational study was carried out recruiting consecutive singleton pregnancies with clinically suspected fetal growth restriction after 34 weeks gestation. The umbilical-cerebral ratios were then calculated from the S/D, RI and PI values and correlated with immediate perinatal outcome.

RESULTS

A total of 187 patients were recruited. Twelve cases had abnormal UA Doppler flow velocity waveform studies. Of the 175 with normal UA Doppler findings, 92 (53.1%) were confirmed to have fetal growth restriction (FGR) with birth weights below the tenth centile for gestation. The detection rate of FGR by ultrasound biometry was 96.7%. The mean umbilical artery S/D, RI and PI values were higher in the fetal growth restriction group, while the middle cerebral artery values were lower as compared to fetuses with no growth restriction. A small but significant difference was seen in the umbilical-cerebral ratios of the different indices between the two groups. Receiver operator characteristic curves showed that there was little difference between the performances of the S/D, RI or PI ratios and all had limited power in predicting fetal growth restriction.

CONCLUSION

In the presence of normal umbilical artery Doppler waveforms, umbilical-cerebral ratios have limited power to predict fetal growth restriction.

Reference ranges for serial measurements of umbilical artery Doppler indices in the second half of pregnancy

OBJECTIVE

The purpose of this study was to construct new reference ranges for serial measurements of commonly used umbilical artery Doppler indices (pulsatility index, resistance index, and systolic:diastolic ratio).

STUDY DESIGN

This was a prospective longitudinal study of the umbilical artery Doppler indices that were obtained serially at the free-loop of umbilical cord at 4-week intervals at 19 to 42 weeks of gestation in 130 low-risk singleton pregnancies. A total of 513 observations were used to construct the reference ranges with the use of multilevel modeling.

RESULTS

Longitudinally established percentiles of Doppler indices from the present study show a continuous reduction throughout the second half of pregnancy without any plateau or increase near term, as reported previously. There was a significant negative association between Doppler indices and placental weight and neonatal birth weight, but not with gender. The intraobserver coefficients of variation for the umbilical artery pulsatility index, resistance index, and systolic:diastolic ratio were 10.5%, 6.8 %, and 13.0 %, respectively.

CONCLUSION

New reference ranges for umbilical artery Doppler indices that are based on longitudinal observations appear to be slightly different from cross-sectional studies and are more appropriate for serial evaluation of fetal hemodynamics.

Fetal growth and well-being

Accurate monitoring of fetal growth is one of the most critically important components of prenatal care. Whether too large or too small for gestational age, the ramifications of abnormal fetal growth have both short-term and long-term sequelae for early neonatal life and beyond. Although not perfectly accurate, ultrasound and other monitoring technologies have markedly improved the ability to follow abnormalities of fetal growth and to decide if early intervention or early delivery is necessary. Clearly, perinatal morbidity and mortality are decreased with close surveillance of these at-risk fetuses.

What antepartum fetal test should guide the timing of delivery of the preterm growth-restricted fetus? A decision-analysis

OBJECTIVE

The purpose of this study was to use a decision-analytic approach to explore the best strategy for the timing of the delivery of preterm intrauterine growth-restricted fetuses.

STUDY DESIGN

We constructed a decision-analysis model that compared 4 antenatal fetal testing strategies The fetal/neonatal states that were compared included live in utero pregnancy; fetal death; neonatal death; disabled neonate, and healthy neonate. Probability estimates for these states and sensitivity and specificity for Doppler velocimetry and biophysical profile were derived from literature review. Sensitivity analyses were performed on the baseline assumptions.

RESULTS

Under the baseline assumptions, biophysical profile was the best test to guide decisions on delivery. Sensitivity analyses revealed the model to be sensitive only to the specificity of a biophysical profile <82%.

CONCLUSION

Compared with the other options, biophysical profile was the best strategy to guide physicians on the timing of the delivery of the preterm growth-restricted fetus.

Decreased fetal movements: background, assessment, and clinical management

A reduction or cessation of fetal movements (FMs) is frequently reported by pregnant women and causes concern and anxiety. However, the clinical significance of a history of reduced FMs remains unclear, and the assessment and management of these pregnancies is controversial. This article is a review of the literature on decreased FMs found in medline and the cochrane library using the search phrases: decreased FMs, perinatal outcome, FM monitoring, and fetal assessment. Formal counting of FMs by the pregnant woman could possibly identify the fetuses, which are at risk of compromise, thus allowing for appropriate action. However, the benefit of this intervention has not been definitely proven. Cardiotocography, umbilical/uterine artery Doppler velocimetry, and ultrasonography have been used for antepartum fetal assessment in pregnancies with decreased FMs, but the evidence of a clinical benefit is limited. The effects of fetal assessment with vibroacoustic stimulation and biophysical profile are unknown and should be further evaluated. Present recommendations on the management of pregnancies with decreased FMs are based on limited and inconsistent scientific evidence. There is a need for further well-designed studies in order to provide evidence-based guidelines in the future.

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.

A randomized clinical trial of the intrapartum assessment of amniotic fluid volume: amniotic fluid index versus the single deepest pocket technique

OBJECTIVE

The purpose of this study was to determine whether an intrapartum assessment of amniotic fluid identifies a pregnancy that is at risk for an adverse outcome.

STUDY DESIGN

Parturients who were admitted for delivery were assigned randomly to have the amniotic fluid assessed either by amniotic fluid index or by the presence of a 2 x 1 pocket.

RESULTS

The amniotic fluid index was obtained in 499 pregnancies, and the 2 x 1 technique was performed in 501. Oligohydramnios was diagnosed in 25% of amniotic fluid index pregnancies versus 8% with the use of the 2 x 1 pocket technique (P <.001). Both techniques failed to identify patients who underwent an amnioinfusion for fetal distress (P=.864) or who experienced variable (P=.208) or late decelerations (P=.210) that influenced delivery, fetal distress in labor (P=.220), caesarean delivery for fetal distress (P=.133), and admission to neonatal intensive care unit (P=.686).

CONCLUSION

Neither the amniotic fluid index nor the 2 x 1 pocket technique that was undertaken as a fetal admission test identifies a pregnancy that is at risk for an adverse outcome.

ILLUSTRATIVE ESTIMATES OF COSTS AND EFFECTS OF THE USE OF DOPPLER ULTRASONOGRAPHY IN HIGH-RISK PREGNANCIES

Objectives: To examine the cost-effectiveness of Doppler ultrasonography in high-risk pregnancies.

Methods: An analysis was made of the cost-effectiveness of Doppler ultrasonography in high-risk pregnancies in relation to different organizational models. National costs of Doppler ultrasonography for singleton pregnancies with intrauterine growth retardation were estimated for three models. The cost-effectiveness analysis was based on results from a meta-analysis on clinical effects, patient costs, immediate health care costs, and costs per “saved” perinatal death.

Results: In the decentralized model (the current situation in Denmark), incremental health care costs were estimated to be 13.5 million DKK, with patient costs set at zero. In the regional and centralized models, the estimated costs were 9.3 million/0.9 million DKK and 3.4 million/2.6 million DKK, respectively. The incremental costs were more than outweighed by the savings made from significant reductions in obstetric interventions. The centralized model dominated the other two models in the cost-effective analysis. In the decentralized model, the costs of avoiding one perinatal death were estimated to be 1 million DKK. The sensitivity analysis suggested that the cost-effectiveness ratio differed considerably, depending on the assumptions used, although the rank order of the three models did not change.

Conclusions: The cost-effectiveness analysis showed that a centralized model with five obstetric centers offering Doppler ultrasonography dominates the regional and decentralized models. However, even with the decentralized model (which reflects the current situation in Denmark), the costs of avoiding one perinatal death would seem to be reasonable. In view of the paucity of available cost and effects data and the sensitivity of the results to changes in the assumptions made, more reliable information is needed before a decision can be made regarding the organization of Doppler ultrasonography for high-risk pregnancies.

Antenatal fetal surveillance

PURPOSE OF REVIEW

Antenatal fetal surveillance is a field of increasing importance in modern obstetrics, especially as results in perinatal care have recently made dramatic progress. It is an evolving field, and it is no longer acceptable just to wait and see when problems arise in pregnancy. During the past few decades many studies have shown that antenatal surveillance in unselected populations is of little value. However, high-risk patients benefit from antenatal fetal surveillance, especially women with pregnancy problems associated with intrauterine growth restriction.

RECENT FINDINGS

This review shows that modern antenatal fetal surveillance is based on fetal heart rate monitoring, ultrasound biometry and amniotic fluid assessment, Doppler blood flow studies of fetal and uteroplacental circulation, and an evaluation of biophysical fetal parameters.

SUMMARY

Used in combination these methods lead to improvements in fetal morbidity and mortality. The aim of future research should be to minimize the risks of fetal morbidity and mortality further by the optimal timing of delivery. Better organization of healthcare systems may improve our ability to identify at-risk patients during pregnancy. There is potential to improve the specificity of fetal surveillance tests, e.g. better methods of biometry and amniotic volume estimation with three-dimensional ultrasound and measurements of subcutaneous tissue. Improved knowledge of fetal physiology can be gained from research on fetal circulation with Doppler studies. Computer analysis of the fetal heart rate can increase the specificity of that test, and artificial neural networks may enhance the ability to evaluate the optimal use of integrated testing.

Previous preterm and small-for-gestational-age births and the subsequent risk of stillbirth

BACKGROUND

Some causes of stillbirth may also lead to fetuses that are small for gestational age (have a low birth weight with respect to their gestational age) or are delivered preterm (before 37 weeks of gestation). It is not known whether the birth of a previous small-for-gestational-age or preterm infant increases the subsequent risk of stillbirth.

METHODS

We assessed the associations between previous adverse outcomes of pregnancy and the risk of stillbirth in a nationwide Swedish study of 410,021 women who delivered first and second consecutive singleton infants between 1983 and 1997. There were 1842 and 1062 stillbirths during the first and second pregnancies, respectively.

RESULTS

As compared with women whose first infant was born at term (37 weeks of gestation or more) and was not small for gestational age, women whose first infant was born at term or preterm and was small for gestational age had an increased risk of stillbirth during their second pregnancy. The odds ratios for subsequent stillbirth, after adjustment for covariates known to be associated with an increased risk of stillbirth, were 2.1 (95 percent confidence interval, 1.6 to 2.8) among women with a first infant who was born at term and was small for gestational age, 3.4 (95 percent confidence interval, 2.1 to 5.6) among women with a first infant who was moderately (32 to 36 weeks of gestation) preterm and small for gestational age, and 5.0 (95 percent confidence interval, 2.5 to 9.8) among women with a first infant who was very (before 32 weeks of gestation) preterm and was small for gestational age. The odds ratio for subsequent stillbirth among women with a first stillborn infant was 2.5 (95 percent confidence interval, 1.4 to 4.7), as compared with women whose first infant was not stillborn. The rates of stillbirth in second pregnancies ranged from 2.4 per 1000 births among women whose first infant was born at term and was not small for gestational age to 19.0 per 1000 births among women whose first child was very preterm and was small for gestational age.

CONCLUSIONS

Delivery of a previous small-for-gestational-age infant is an important predictor of the subsequent risk of stillbirth, particularly if the infant was delivered preterm.

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.

Doppler ultrasonography in singleton pregnancies at risk of intrauterine growth retardation-- a national estimate

BACKGROUND

In order to assess the organizational and economical implications of Doppler ultrasonography used in high risk pregnancies, a national estimate of the use in singleton pregnancies with risk of small for gestational age (>2 SD below mean birthweight) (SGA) or intrauterine growth retardation (IUGR) was needed.

METHODS

Through retrospective analyzes of both national registry data, and local clinical and ultrasonic records from Copenhagen University Hospital annual populations of singleton pregnant women with suspected IUGR and/or infants born SGA were described. The antenatal care program for assessing pregnancies with suspected IUGR was described.

RESULTS

In 1996 2.8% of all singleton infants were born SGA. The population had increased risk of perinatal mortality and morbidity, and about 40% had labor induced or were delivered by caesarean section, compared to 15% of the infants with normal birthweight. In the local population 79 (3.3%) of singleton infants were born SGA and 2/3 of these were considered SGA or IUGR before delivery. Of all singleton pregnancies, a total of 88 (3.7%) were assessed by ultrasonic fetometry because of a risk or clinical suspicion of SGA, and 49 (55.7%) of these pregnancies resulted in a SGA infants. Combining national and local data it is estimated that in Denmark, about 2000 women (3.1%) will be referred for ultrasonic fetometry each year because of a risk or clinical suspicion of SGA and have a mean of 2.5 fetometries. About 75% (1500) will be further assessed by Doppler ultrasonography and have a mean of 3.4 Doppler examinations.

CONCLUSION

The annual number of Doppler ultrasonography examinations in singleton pregnancies with increased risk of or signs of IUGR is estimated to be about 5000.

Intrauterine growth restriction

Pathophysiological processes underlying intrauterine growth restriction are very complex and poorly understood. Growth restricted fetuses are at risk of hypoxia and, therefore, an early diagnosis of intrauterine growth restriction is important for initiation of fetal surveillance. Application of a three-dimensional ultrasound method for estimation of fetal weight promises better precision. Use of conditional standard deviation scores of fetal biometric variables has been suggested for improved individualized evaluation of intrauterine growth. Application of umbilical artery Doppler velocimetry in the clinical management of growth-restricted fetuses after 32 weeks of gestation leads to decreased perinatal mortality and lower rates of obstetric interventions. Evaluation of fetal state before 32 weeks is difficult and should include Doppler examination of placental circulation and several fetal arterial and venous vessel beds. In addition, recordings of short-term variability of fetal heart rate and biophysical profile have been suggested for fetal surveillance. Important new data on the time sequence of Doppler changes in various vessels of compromised very preterm growth restricted fetuses have been presented, which will enable the establishment of clinical management protocols for evaluation in prospective randomized studies.

Uterine and fetal cerebral Doppler predict the outcome of third-trimester small-for-gestational age fetuses with normal umbilical artery Doppler

OBJECTIVE

To assess the value of different admission tests in predicting the outcome of small-for-gestational age (SGA) fetuses with normal Doppler waveforms in the umbilical artery.

METHODS

Criteria for admission into this retrospective study included: singleton pregnancy with a birth weight < 10th centile; absence of severe maternal complications; no evidence of fetal anomalies on the sonogram; normal umbilical artery Doppler; and availability of complete follow-up. At the first antenatal sonogram classifying the fetus as SGA, Doppler analysis of the uterine and middle cerebral arteries was performed and amniotic fluid volume was assessed. Outcome variables included adverse perinatal outcome (perinatal death, severe morbidity) and emergency Cesarean section for fetal distress.

RESULTS

Two hundred and thirty-one pregnancies were included in the study. The mean +/- standard deviation birth weight and gestational age at delivery were 2222 +/- 502 g and 37.3 +/- 2.9 weeks, respectively. In 37 cases (16%), an emergency Cesarean section was performed. There was one intrauterine death and three fetuses delivered by emergency Cesarean section developed severe morbidity. Logistic regression demonstrated that abnormal velocimetry of the uterine arteries and fetal middle cerebral artery were independently correlated with the occurrence of Cesarean section.

CONCLUSIONS

SGA fetuses with normal umbilical artery Doppler waveforms and abnormal uterine arteries and fetal middle cerebral artery waveforms have an increased risk of developing distress and being delivered by emergency Cesarean section. Particularly when both uterine and fetal cerebral waveforms are altered at the same time, the risk is exceedingly high (86%) and delivery as soon as fetal maturity is achieved seems advisable. On the other hand, when both vessels have normal waveforms, the chances of fetal distress are small (4%) and expectant management is the most reasonable choice.