The clinical implications of absent or reversed end-diastolic frequencies in umbilical artery flow velocity waveforms

No. 197a-Fetal Health Surveillance: Antepartum Consensus Guideline

OBJECTIVE

This guideline provides new recommendations pertaining to the application and documentation of fetal surveillance in the antepartum period that will decrease the incidence of birth asphyxia while maintaining the lowest possible rate of obstetrical intervention. Pregnancies with and without risk factors for adverse perinatal outcomes are considered. This guideline presents an alternative classification system for antenatal fetal non-stress testing to what has been used previously. This guideline is intended for use by all health professionals who provide antepartum care in Canada.

OPTIONS

Consideration has been given to all methods of fetal surveillance currently available in Canada.

OUTCOMES

Short- and long-term outcomes that may indicate the presence of birth asphyxia were considered. The associated rates of operative and other labour interventions were also considered.

EVIDENCE

A comprehensive review of randomized controlled trials published between January 1996 and March 2007 was undertaken, and MEDLINE and the Cochrane Database were used to search the literature for all new studies on fetal surveillance antepartum. The level of evidence has been determined using the criteria and classifications of the Canadian Task Force on Preventive Health Care (Table 1).

SPONSOR

This consensus guideline was jointly developed by the Society of Obstetricians and Gynaecologists of Canada and the British Columbia Perinatal Health Program (formerly the British Columbia Reproductive Care Program or BCRCP) and was partly supported by an unrestricted educational grant from the British Columbia Perinatal Health Program. RECOMMENDATION 1: FETAL MOVEMENT COUNTING: RECOMMENDATION 2: NON-STRESS TEST: RECOMMENDATION 3: CONTRACTION STRESS TEST: RECOMMENDATION 4: BIOPHYSICAL PROFILE: RECOMMENDATION 5: UTERINE ARTERY DOPPLER: RECOMMENDATION 6: UMBILICAL ARTERY DOPPLER.

Current concepts in intrauterine growth restriction

Regulation of fetal growth is multifactorial and complex. Diverse factors, including intrinsic fetal conditions as well as maternal and environmental factors, can lead to intrauterine growth restriction (IUGR). The interaction of these factors governs the partitioning of nutrients and rate of fetal cellular proliferation and maturation. Although IUGR is probably a physiologic adaptive response to various stimuli, it is associated with distinct short- and long-term morbidities. Immediate morbidities include those associated with prematurity and inadequate nutrient reserve, while childhood morbidities relate to impaired maturation and disrupted organ development. Potential long-term effects of IUGR are debated and explained by the fetal programming hypothesis. In formulating a comprehensive approach to the management and follow-up of the growth-restricted fetus and infant, physicians should take into consideration the etiology, timing, and severity of IUGR. In addition, they should be cognizant of the immediate perinatal response of the growth-restricted infant as well as the childhood and long-term associated morbidities. A multi disciplinary approach is imperative, including early recognition and obstetrical management of IUGR, assessment of the growth-restricted newborn in the delivery room, possible monitoring in the neonatal intensive care unit, and appropriate pediatric follow-up. Future research is necessary to establish effective preventive, diagnostic, and therapeutic strategies for IUGR, perhaps affecting the health of future generations.

Predictive value of serial middle cerebral and renal artery pulsatility indices in fetuses with oligohydramnios

OBJECTIVE

To determine if unexplained changes in the amniotic fluid index or pulsatility indices of the fetal renal, middle cerebral, or umbilical artery are predictive of perinatal outcome in pregnancies complicated by oligohydramnios.

METHODS

Changes in amniotic fluid measurements and fetal vessel velocimetry in patients with oligohydramnios were evaluated for correlation with fetal outcome. Fourteen fetuses with oligohydramnios underwent serial sonography evaluating the amniotic fluid index and fetal middle cerebral, renal, and umbilical velocimetry. Matched controls and neonatal outcomes were obtained.

RESULTS

Change in amniotic fluid index and in renal artery pulsatility index were inversely correlated. Change in the middle cerebral artery pulsatility index was different in infants with normal outcome compared to infants with adverse outcome

CONCLUSIONS

Serial velocimetry of the middle cerebral artery may identify fetuses with oligohydramnios at risk for adverse outcomes.

Absence of end-diastolic flow velocity in the umbilical artery: a review

The objective of this review was to find the clinical relevance of the absence of end-diastolic flow velocity in the umbilical artery. Search was conducted through MEDLINE using unabridged MEDLINE Knowledge Finder (Aries System Corp., North Andover, MA). All the manuscripts published in English language within last 10 years (1983-1992) were included in the review process. There has been no report of umbilical artery absent-end diastolic velocity before 1983. It was extremely difficult to draw a conclusion because a majority of the available reports in the literature are either case reports or retrospective analyses. However, for the practical purposes it can be concluded that after viability these pregnancies should be followed by intense (daily) fetal well-being surveillance with conventional antenatal tests. Those who improve their end-diastolic velocity should be allowed to continue the pregnancy as long as antenatal testing is promising. Persistence of absent end-diastolic velocity may be an indication for delivery at a gestational age when there is reasonable chance of survival. Cytogenetic evaluation and anatomical survey of these fetuses by ultrasound is recommended. Long-term follow up of surviving infants needs to be studied. It is impossible for a single institution to accumulate enough cases for adequate outcome evaluation. A randomized prospective trial to assess the management of pregnancies with absent end-diastolic velocity in the umbilical artery would be difficult. Some might even consider such a study unethical. Until such a study is performed, an international registry would be helpful for collecting data about the perinatal outcomes and management of such patients.

Fetal umbilical Doppler in a population of 541 high-risk pregnancies: prediction of perinatal mortality and morbidity. Doppler Study Group

OBJECTIVE

To evaluate the usefulness of systematic umbilical Doppler in the assessment of high-risk pregnancies.

METHOD

In a prospective multicentre study, a group of high-risk pregnancies (intrauterine growth retardation, hypertension during pregnancy, abnormal obstetric history) was systematically studied by Doppler exploration of the fetal umbilical artery between 28 and 34 weeks. All the details of pregnancy development to the first postnatal days were collected and analysed a posteriori.

RESULTS

Three groups were formed according to Doppler results (Index S-D/S) A, index < 90th percentile (n = 458, 84.6%); B, index > or = 90th percentile and diastole over zero (n = 67, 12.4%); C, zero diastole (n = 16, 2.9%). There was a strong correlation between Doppler results and pregnancy development. Group C corresponded to a greatly altered prognosis (hypotrophy, < 3rd percentile in 69%; intrauterine deaths in 9/16). In group B, relative to group A, the prognosis was significantly altered (hypotrophy, 24% versus 6%, P < 0.01; prematurity rate, 25% versus 11%, P < 0.001) but these repercussions were not as severe as in group C.

CONCLUSION

In high-risk pregnancies, fetal umbilical artery Doppler study is of interest for prognostic assessment. Normal results should provide temporary reassurance. Abnormal umbilical Doppler indicates that chronic suffering will occur or is onset in at least one-third of cases.

The role of Doppler velocimetry in the management of high risk pregnancies

OBJECTIVE

To determine whether knowledge of the result of Doppler velocimetry of the umbilical artery is beneficial to the management of a high risk pregnancy.

DESIGN

Randomised controlled trial. The trial was of the management type, designed to assess benefit accruing from additional information supplied by Doppler velocimetry.

SETTING

Tygerberg Hospital, Cape Town, South Africa. The hospital serves a population from the lower socio-economic groups.

SUBJECTS

Women with pregnancies 28 or more weeks gestation with hypertensive diseases and/or suspected small for gestational age fetuses were referred for Doppler velocimetry. From this population, three subsets were formed: 1. those with fetuses with absent end-diastolic velocities (20 fetuses); 2. those with hypertension but with fetuses with end-diastolic velocities (89 fetuses); and 3. those with fetuses suspected of being small for gestational age but with end-diastolic velocities (104 fetuses).

INTERVENTIONS

Doppler velocimetry on all subjects. The study group consisted of 10 cases with absent end-diastolic velocities, 47 cases with hypertensive diseases with end-diastolic velocities and 51 cases with suspected small for gestational age fetuses but with end-diastolic velocities in which the result was revealed to the clinician. The control group consisted of 10, 42 and 53 cases, respectively, in which the Doppler results were not revealed. All other routine investigations (sonar and antenatal fetal heart rate monitoring) were available to the clinicians. Standard management protocols were followed in all groups.

MAIN OUTCOME MEASURES

Perinatal mortality and morbidity, antenatal hospitalisation, maternal intervention, admission to the neonatal intensive care unit and hospitalisation until discharge from the neonatal wards.

RESULTS

In the study and control groups the gestational age at entry to the study, maternal age, parity and various complications were not significantly different. In the subset with absent end-diastolic velocities, there was one neonatal death in the study group, but in the control group there were six deaths, five intrauterine and one perinatally related infant death (P = 0.029). Because of this significant finding, the study was stopped. There were no differences in outcome in the subset where there was hypertensive disease with end-diastolic velocities between the study and control groups. In the subset in which small for gestational age fetuses were suspected, but in which end-diastolic velocities were present, the women in the study group had significantly fewer days in hospital before delivery (P < 0.001) and tended to have fewer maternal interventions (study group = 27%, control group = 43%; P = 0.07; odds ratio (OR) 0.49, 95% confidence limits (CL) 0.2 and 1.25) and caesarean sections (study group = 13%, control group = 27%; P = 0.08; OR 0.43, 95% CL 0.14 and 1.32). The infants of the study group in this subset also spent significantly less time in the neonatal wards (P = 0.029).

Doppler velocimetry in pregnancy

Since the late 1970s, Doppler velocimetry has been investigated extensively for use in obstetrics. Initially, this technique showed promise for the management of certain complications of pregnancy; this promise has yet to be fulfilled. Doppler velocimetry of either the uterine or umbilical vessels, which showed some merit in selecting growth-retarded fetuses at particular risk, has neither become a screening tool for intrauterine growth retardation nor proven clinically successful in improving fetal outcome. Likewise, its use for other complications of pregnancy (eg, postdate pregnancy, twin pregnancy, and diabetes) has not led to improved pregnancy outcome. More recently this technique has been used to study other vascular beds. Changes in the Doppler characteristics of these vascular beds may demonstrate the fetal response to its environment. These investigations provide the potential for a better understanding of fetal physiology; however, it has yet to be shown by prospective evaluation that their application results in improved pregnancy outcome. This review defines the uses and limitations of Doppler ultrasound in current obstetric practice.

The effect of introduction of umbilical Doppler recordings to obstetric practice

OBJECTIVE

To assess the effect on obstetric practice of clinician access to umbilical artery Doppler ultrasound results.

DESIGN

Randomised controlled trial.

SETTING

A large teaching hospital.

SUBJECTS

Two thousand two hundred and eighty-nine pregnancies defined as being at risk by referral for Doppler or fetal monitoring.

INTERVENTIONS

Continuous wave Doppler studies of umbilical artery. Results immediately available to clinicians.

MAIN OUTCOME MEASURES

Fetal outcome: perinatal mortality, Apgar score and admission to the neonatal unit. Obstetric intervention: admission to hospital, induction of labour and caesarean section. Use of of fetal well being: cardiotocography, biophysical profile and ultrasound biometry.

RESULTS

The treatment and control groups were comparable in age, parity, gestation at point of entry and risk features. There were no overall differences in perinatal outcome, obstetric intervention or use of fetal monitoring. Examination of a subset recruited only because of hypertension or suspected intrauterine growth retardation (n = 754) similarly showed no difference attributable to group randomisation. Comparison of only those pregnancies retrospectively defined as low risk and high risk showed more use of cardiotocography in the high risk group with access to Doppler (P = 0.007) but no difference in the low risk group.

CONCLUSION

Doppler umbilical artery recording has been shown to perform well in prediction power of antenatal fetal compromise. What has been examined in this study is the response of clinicians to the test. The results suggest that obstetricians do not use the test to modify their risk assessment, and, therefore, the need for fetal monitoring in particular pregnancies. There is a real need for accumulation of information from very large data sets, particularly in the prediction power of Doppler for antenatal fetal compromise from apparently chronic utero-placental cause to guide use of monitoring resources. If simply added to existing fetal monitoring techniques in a hospital where these are widely used, then umbilical artery Doppler recordings may at present simply involve extra resources of staff and expenses, without benefit.

The relationship between absent end-diastolic velocities of the umbilical artery and perinatal mortality and morbidity

To determine the perinatal mortality and neonatal morbidity of fetuses with absent end-diastolic velocities (AEDV) of the umbilical artery, the outcome of 120 fetuses, with a gestational age of 24 weeks or more and a birth weight of 500 g or more, with AEDV at the last Doppler examination, were analyzed. The study population came from 348 women who had pregnancies at high risk of placental insufficiency and had had Doppler velocimetry examinations. In all the women, the Doppler velocimetry result was withheld from the clinician managing the woman. Of the fetuses with AEDV, 57 (52%) died and only 26 (22%) babies had minimal or no neonatal morbidity. All 24 fetuses with AEDVs delivering before 28 weeks gestation and having a birth weight less than 750 g died. When compared with fetuses from the study population with end-diastolic velocities present, the gestational age and birth weight at delivery was significantly lower, and the perinatal mortality, neonatal morbidity and number of light for gestational age (LGA) babies was significantly higher in the AEDV group. The LGA babies from both groups were compared by gestational age category and the LGA babies with AEDV still had a significantly higher perinatal mortality. There was no difference in the pattern of neonatal complications or causes of neonatal deaths between the two groups.

Diastolic zero-flow in the umbilical artery in twin pregnancies

Clinical arterial blood flow measurements in single pregnancies can not be precisely estimated yet. ARED (absent or reverse end diastolic) flow of the umbilical artery (UA) commonly indicates a symptom of fetal jeopardy. The interpretation of blood flow measurement in twin pregnancies is still controversial. On one hand, no differences in a single pregnancies are found, and on the other hand, increased resistance indices have been reported. In the feto-fetal transfusion syndrome mostly there are normal blood flow measurements. When pathological blood flow occurs, usually it affects the donor. By means of 4 case reports with ARED flow, the value of the investigation method in management of twin pregnancies is demonstrated. Three out of four fetuses with an ARED flow in the UA have died. Case fetus with a normal flow velocimetry survived. Even feto-fetal transfusion syndrome may cause pathological blood flow curves. In fetuses with ARED-flow in the UA fetal hypoxia and acidosis are to be expected. A careful evaluation of the cardiotocogram is indicated with a viable fetus. A possible fetal disturbance may be seen early in blood flow curves and may help provide better obstetrical management.

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

Fetal heart rate (FHR) variation, general movements (FGM), breathing movements (FBM) and haemodynamics were studied longitudinally in 19 intrauterine growth retarded fetuses, who eventually were delivered by caesarean section (CS) because of fetal distress, in order to determine changes occurring with time. The fetuses were studied for the last 10 days on average before delivery (range 2-14 days). During this period on average eight 1-h FHR records were made and three 1-h movement recordings. The FHR pattern was analyzed numerically; the incidence of FGM and FBM was quantified and expressed as percentage of time. Blood flow velocity waveforms were measured in the umbilical artery (n = 19) and in the internal carotid artery (n = 14). In 14 of 19 fetuses abnormal velocity wave forms were present from the beginning of the study onwards. FHR variation was initially just within or below the norm and fell further during the last 2 days before CS. FGM and FBM fell below the normal range later and in a lower rate of occurrence than FHR variation. FGM showed a more or less consistent fall in time, whereas FBM showed a wide range throughout the period of observation. The poorest outcome occurred in fetuses with reversed end-diastolic velocities and rapid fall in FHR variation. It is concluded that with progressive deterioration of the fetal condition abnormal velocity wave form patterns occur first; FHR variation is reduced subsequently and FGM and FBM are the last to become abnormal. Assessment of fetal activity may be of help in fetuses with a marginally reduced FHR variation, in which prolongation of pregnancy is considered desirable to allow further maturation in utero.

Fetal cerebral haemodynamic adaptation: a progressive mechanism? Pulsed and color Doppler evaluation

The importance of studying, by Doppler ultrasound, the cerebral haemodynamics to monitor the fetal response to the hypoxia is well known, but there is not a general agreement about the anatomical landmarks for the middle cerebral artery. Seventy-one normal fetuses and fifteen IUGR fetuses were studied. The umbilical artery and the middle cerebral artery (MCA) were evaluated by color Doppler ultrasound. The well-known decrease of the pulsatility index from the umbilical artery was observed throughout pregnancy. This velocimetric pattern did not occur in the IUGR fetuses. Four IUGR fetuses showed the ARED (absent or reversed and diastolic flow) pattern. The MCA was evaluated at the origin (M1) and at the distal tract (M2). PI values from M1 and M2 decreased during the pregnancy. A significant difference was detected between M1 and M2 PI values from the 26th to the 37th week of gestation. The M1 brain sparing effect was detected in the IUGR fetuses. Two ARED fetuses, observed during labor, showed the M2 sparing effect. The different Doppler patterns found in M1 and M2 could be due to the functional differences existing between these tracts. As a matter of fact, M1 and M2 supply different parts of the fetal brain, which develop in different periods of fetal life. These findings, if ulteriorly confirmed, could offer new perspectives for the monitoring of high risk fetuses.