Relationship between monitoring parameters and perinatal outcome in severe, early intrauterine growth restriction

Toward quantitative fetal heart rate monitoring

Continuous electronic fetal heart rate (FHR) monitoring during labor is motivated by the clinical experience that fetal distress causes loss of FHR variation and the occurrence of decelerations late during uterine contraction. This practice is of uncertain clinical benefit, perhaps because the interpretation is qualitative. We have developed new quantitative measures and analyzed cardiotocograph records from 148 consecutive patients, 44 of whom had at least one "nonreassuring" epoch. In multivariate regression models, measures of deceleration and variability were significantly associated with the obstetrician's diagnosis (receiver operating characteristic area 0.84, p < 0.05). This approach may be useful clinically.

Integrated monitoring of fetal growth restriction by computerized cardiotocography and Doppler flow velocimetry

OBJECTIVE

To investigate the correlations between Doppler flow velocimetry and computerized cardiotocography (cCTG) in fetal growth restriction.

STUDY DESIGN

Fifty growth-restricted foetuses with abdominal circumference below the 10th percentile and no major abnormalities were studied. A total of 186 cCTG tracings (at least two per patient) analysed using the HP2CTG system were compared with the corresponding umbilical artery pulsatility index (PI), the PI ratio of umbilical artery to middle cerebral artery, and the ductus venosus systolic/atrial ratio.

RESULTS

Worsening in umbilical artery Doppler velocimetry parameters was associated with a significant reduction of short- and long-term variability indices and accelerations. When end-diastolic umbilical artery flow was preserved, a reversed ratio between umbilical artery and middle cerebral artery PIs was not correlated with a worsening of cCTG parameters; in the presence of umbilical artery absent or reversed flow, ductus venosus Doppler velocimetry abnormalities were correlated with a significant reduction of variability. When end-diastolic umbilical artery flow was preserved, there was a progressive increase in variability indices and accelerations with advancing gestational age. In the more compromised fetuses this "maturation" process of cCTG patterns was not found.

CONCLUSION

There is a strict correlation between Doppler velocimetry abnormalities and cCTG parameter deterioration, in particular between ductus venosus and variability.

Ultrasound and fetal diagnosis

PURPOSE OF REVIEW

The purpose of this review is to highlight publications from the last year that have advanced the use of ultrasound in obstetrics.

RECENT FINDINGS

Anatomic examination of the fetus in the first trimester has been emphasized because it allows for early diagnosis of many conditions. The prevalence of absent nasal bone, a marker for trisomy 21, in euploid fetuses depends on ethnicity. Nasal bone hypoplasia is another marker for Down syndrome. Studies on genetic screening in the first trimester have involved various serum analytes, adjustments in timing and calculations, use in multiple gestations, and the association of extreme measurements with adverse outcomes. A first-trimester integrated screening approach, which incorporates nuchal translucency, nasal bone, crown-rump length, pregnancy-associated plasma protein-A, and free beta-human chorionic gonadotropin, has the potential to maximize detection rates of Down syndrome and trisomy 18 and minimizes the screen-positive rate. The value of combining first and second-trimester results in sequential, contingent, or integrated screening protocols has been assessed. Isolated mild ventriculomegaly (10-12 mm) may prove to be a normal variant, and the role of 'soft' ultrasound markers in genetic counseling continues to be debated. Anomaly or high-risk status detection in the second trimester has been enhanced by the use of Doppler, 3D/4D ultrasound, and magnetic resonance imaging.

SUMMARY

Imaging techniques have been critical in the development of screening methods for Down syndrome or trisomy 18 and for euploid fetuses at high risk for adverse outcomes.

Doppler, Cardiotocography, and Biophysical Profile Changes in Growth-Restricted Fetuses

OBJECTIVE

To assess from diagnosis to delivery the Doppler studies of the umbilical artery, middle cerebral artery, umbilical vein, ductus venosus, and amniotic fluid index of fetuses with idiopathic growth restriction.

METHODS

A total of 145 singleton growth-restricted fetuses with abnormal umbilical artery pulsatility indexes were studied. Cesarean delivery was performed because of abnormal biophysical profile or nonreassuring fetal heart rate pattern.

RESULTS

There were 4 fetal and 50 neonatal deaths. Two growth-restricted groups were identified: Group A (n = 44) included fetuses in whom all measures became abnormal preceding an abnormal biophysical profile or nonreassuring nonstress test. Group B (n = 101) included fetuses in whom 1 or more measures were normal at the time of cesarean delivery. There was no statistically significant difference in perinatal morbidity and mortality between the 2 groups. Neonatal death was increased in fetuses with umbilical artery reversed flow (odds ratio 2.34, 95% confidence interval 1.16-4.73; P < .05) and ductus venosus reversed flow (odds ratio 4.18, 95% confidence interval 2.01-8.69; P < .05). A significant correlation was also found between low birth weight and adverse perinatal outcome.

CONCLUSION

In fetuses with idiopathic growth restriction, 1) low birth weight, 2) umbilical artery reversed flow, and 3) ductus venosus absent or reversed flow are associated with an increased perinatal morbidity and mortality.

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.

Antenatal predictors of neonatal outcome in fetal growth restriction with absent end-diastolic flow in the umbilical artery

OBJECTIVE

Absent end-diastolic blood flow in the umbilical artery identifies growth-restricted fetuses at high risk of perinatal mortality and severe morbidity. We explored antenatal variables predictive of perinatal mortality or severe neonatal morbidity in such fetuses.

STUDY DESIGN

We accessed a cohort of 39 singleton, non-malformed, growth-restricted fetuses with absent end-diastolic blood flow at less than 34 weeks between January 1995 and December 2004. The ratio of umbilical artery pulsatility index to middle cerebral artery pulsatility index was calculated to assess redistribution of the fetal arterial circulation. Prenatal and neonatal variables were compared between subjects with versus those without perinatal mortality or severe morbidity using unpaired Student t test or Fisher exact test. Statistical analysis included stepwise logistic regression and receiver operating characteristic curve analysis. P < .05 was considered significant.

RESULTS

Stepwise logistic regression analysis demonstrated that the last umbilical artery/middle cerebral artery ratio (P = .02) and estimated fetal weight before delivery (P = .02) were independent predictors of adverse neonatal outcome, with an umbilical artery/middle cerebral artery ratio 1.9 or greater having a sensitivity of 75% and a 13% false-positive rate. Umbilical artery/middle cerebral artery ratio alone accounted for 54% of the variability in outcome.

CONCLUSIONS

Among preterm growth-restricted fetuses with absent end-diastolic blood flow in the umbilical artery, the umbilical artery/middle cerebral artery ratio is the best predictor of neonatal mortality or severe morbidity.

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.

Intrauterine growth restriction

PURPOSE OF REVIEW

Intrauterine growth restriction remains one of the major problems in obstetrics. Recent published literature on this problem is summarized in this review.

RECENT FINDINGS

Intrauterine growth restriction contributes disproportionately to neonatal mortality and morbidity in both preterm and term babies, and is a predisposing factor to major psychiatric sequelae such as depression, suicide and suicidal attempts. More evidence is accumulating to show that fetal Doppler changes of the ductus venosus and umbilical vein are good surrogate markers for fetal academia. The timing of delivery remains controversial, however. The Growth Restriction Intervention Trial showed that delayed delivery in those up to 30 weeks may be associated with lower rates of cerebral palsy and Griffiths development quotient under 70. In dichorionic twins, selective fetocide of one severe intrauterine growth restriction fetus in midtrimester twin pregnancies complicated by severe preeclampsia may abort the disease process and prolong the pregnancy. For monochorionic twins, the finding of intermittent absent or reversed end diastolic flow in the umbilical artery may be a manifestation of the transmission of the bi-directional waveforms of arterio-arterial anastomosis, but has been shown to be associated with an increased risk of intrauterine death in the growth restricted fetus and brain damage in the larger fetus.

SUMMARY

The timing of delivery of the preterm growth restricted fetus remains controversial. Intrauterine growth restriction with intermittent absent or reversed end diastolic flow in the umbilical artery of monochorionic twins poses difficulties in assessment.

Diagnosis and management of intrauterine growth restriction

The growth-restricted fetus is a fetus who fails to reach his growth potential and is at risk for perinatal morbidity and mortality. When a fetus has an estimated weight below the 10th percentile, in the absence of congenital anomalies and in the presence of a normal amount of amniotic fluid, Doppler velocimetry gives the most important information to differentiate the truly growth-restricted fetus from the fetus that is constitutionally small but otherwise normal. One area of debate and research is whether Doppler velocimetry can help in timing the delivery of the growth-restricted fetus. Data appear to support the use of ductus venosus velocimetry in deciding when to deliver, but randomized data on this point are still lacking.

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.

Doppler application in the delivery timing of the preterm growth-restricted fetus: another step in the right direction

This article provides an opinion on a study of relationships between umbilical artery (UA) Doppler, ductus venosus (DV) Doppler, fetal heart rate variation, and perinatal outcome in preterm, intrauterine growth-restricted (IUGR) fetuses published in the same issue of this journal by Bilardo and coworkers. Recent evidence on venous Doppler surveillance in preterm IUGR fetuses was also reviewed and discussed in the context of the study with a special emphasis on delivery timing. A search was conducted through MEDLINE and eight articles with similar inclusion criteria and reporting format of outcomes were identified. Numbers for perinatal mortality, intraventricular hemorrhage, respiratory distress syndrome, bronchopulmonary dysplasia and necrotizing enterocolitis (NEC) were extracted for cases where Doppler status was recorded in an identical format. Proportional distribution of outcomes was compared for fetuses with normal DV Doppler velocimetry, absent or reversed UA end-diastolic velocity (UA A/REDV), elevated DV Doppler index (abnormal DV) and absence or reversal of atrial velocity in the DV (DV-RAV). A total of 320 fetuses with normal and 202 with elevated DV Doppler indices were extracted. Of these fetuses, 101 with UA A/REDV only and 34 with DV-RAV were identified. Perinatal mortality was 5.6% (16/282) with normal DV, 11.9% (12/101) with UA A/REDV, 38.8% (64/165) with abnormal DV and 41.2% (7/17) with DV-RAV. With the exception of NEC, all complications were significantly more frequent with abnormal DV. With normal venous Doppler neonatal deaths account for most of the perinatal mortality, while with abnormal DV stillbirths and neonatal mortality are similar contributors to the significantly increased perinatal mortality. In conclusion, UA Doppler is a placental function test that provides important diagnostic and prognostic information in preterm IUGR. DV Doppler effectively identifies those preterm IUGR fetuses that are at high risk for adverse outcome (particularly stillbirth) at least 1 week before delivery, independent of the UA waveform. Relationships between perinatal outcome, arterial and venous Doppler status and gestational age require ongoing observational research effort. Randomized management trials are necessary to verify that delivery timing based on venous Doppler will impact on outcome in preterm IUGR.