Antepartum improvement of abnormal umbilical artery velocimetry: does it occur?

Does increased resistance on umbilical artery Doppler preclude a trial of labour?

OBJECTIVE

To determine whether patients with increased resistance on umbilical artery Doppler velocimetry could be safely allowed a trial of labour.

DESIGN

The Coombe Womens' Hospital is a university teaching hospital which takes tertiary referrals. All singleton pregnancies found to have increased resistance (>2 SD above the mean for gestational age) on umbilical artery Doppler ultrasound between 1993 and 1995 inclusively were identified from the ultrasound database and reviewed, retrospectively. Cases where the umbilical artery waveform reverted to normal or deteriorated to absent end diastolic flow on a subsequent scan were excluded. The 118 cases identified were divided into two groups, those that were delivered by elective caesarean section and those that laboured.

RESULTS

Forty-five patients were delivered by elective caesarean section and 73 were allowed to labour. In the group that laboured over 90% delivered vaginally and 9.8% were delivered by emergency caesarean section. Three babies had a cord pH less than 7.20 in the group that laboured. Two babies had an Apgar score of less than 7 at 5 min in the group that were delivered electively. There were no neonatal seizures or perinatal deaths in either of the two groups.

CONCLUSIONS

This study shows that patients with increased resistance on umbilical artery Doppler can be allowed a trial of labour without compromising the fetal outcome. We would suggest that consideration be given to induction of labour in selected patients as an alternative to elective section.

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.

Absent end diastolic flow of umbilical artery Doppler: pregnancy outcome in 62 cases

We retrospectively studied the outcome of pregnancy in 62 cases of absent end diastolic flow (AEDF) of umbilical artery Doppler flow velocity waveform. The history of pregnancies revealed that nearly all were of high risk. Many cases presented cerebral (65%) or uterine (55.5%) Doppler flow abnormalities, or both (38%). We noted 10 fetal deaths and decided 7 pregnancy terminations. Malformation and chromosomal defect rate was 16%. We noted 44 (71%) live-births, a very high rate of cesarean section (86%), prematurity (75%), small for gestational age (39%). Forty-five percent of the neonates had a 1-min Apgar score under 7, which dropped to 27% at 5 min. Neonate mortality rate was 6.9% and the total mortality rate was 34% (21/62). Morbidity was significant (7 cases with severe morbidity, 2 cases with chromosomal abnormality of poor prognosis). We compared different sub-groups with a view to looking for some prenatal factors which predict poor neonatal outcome in case of AEDF.

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.

Uteroplacental Doppler ultrasound in routine antenatal care

Three hundred and five pregnant women referred consecutively from a single antenatal clinic for imaging ultrasound after 26 weeks' gestation had doppler velocimetry of umbilical artery, uterine artery and umbilical vein. Results of doppler studies were not available to clinicians until after delivery and clinical case records were examined postpartum for the development of pregnancy-induced hypertension (PIH) or gestational diabetes mellitus (DM) and for fetal outcome. Accurate data were available for 272 women, of whom 167 had a normal pregnancy, 61 had or developed PIH and 44 had or developed DM. None of the various doppler velocimetry measurements differed significantly amongst these 3 groups at any gestational stage. Abnormal values for doppler systolic: diastolic (A/B) ratio were found in only 7% of umbilical artery measurements, 6% of uterine artery measurements and none of umbilical vein measurements. Specificity of abnormal results for PIH or DM was high (95-97%) but sensitivity low (16-17%) and positive and negative predictive values were generally low. Two perinatal deaths occurred and umbilical artery A/B ratio was abnormal in both cases. This study shows that there is a low yield of abnormal results for doppler velocimetry of umbilical artery, uterine artery or umbilical vein in routine antenatal screening.

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

We describe the clinical details of 37 pregnancies with loss or reversal of end-diastolic frequencies in the umbilical artery, as detected by Doppler ultrasound. This finding is an ominous sign of serious fetal compromise in the majority of cases, with a high incidence of growth retardation, oligohydramnios, preterm delivery and maternal hypertension. However, current knowledge does not indicate when these pregnancies should be delivered. The possible pathophysiology and available literature are discussed.

Limited role of fetal blood sampling in prediction of outcome in intrauterine growth retardation

Fetal acid-base status was evaluated on 66 blood samples taken for rapid karyotyping from 58 growth-retarded fetuses. Before blood sampling, doppler blood flow studies of the umbilical artery showed end-diastolic frequencies to be absent in 32 fetuses (group 1) and present in 26 (group 2). Fetuses with chromosomal (n = 4) or structural (n = 8) abnormalities were excluded from subsequent analysis. Gestational age at blood sampling (27.8 [95% CI 26.5-29.1] vs 32.2 [30.4-34.1] weeks) and time from sampling to delivery (median 2 (range 0-35] vs 14 [0-77] days) were significantly lower in group 1 than group 2. There were no perinatal deaths in group 2 whereas mortality in group 1 was 65.4%. There were significant differences between the groups at blood sampling in pH, pO2, pCO2, base equivalents, and nucleated-red-cell count, but within group 1 these measurements were similar in surviving fetuses and those who died perinatally. Since acid-base determination does not predict perinatal outcome in growth-retarded fetuses, fetal blood sampling has a limited role in monitoring fetal wellbeing.

Clinical management of the fetus with markedly diminished umbilical artery end-diastolic flow

This study was conducted to evaluate prospectively a management protocol for fetuses with a markedly abnormal umbilical artery velocity waveform. The study population consisted of fetuses whose systolic/diastolic ratio was greater than 2 SD above the mean for gestational age. The matched control population consisted of fetuses with similar gestational ages, indications for testing, and estimated fetal weights with normal systolic/diastolic ratios. Abnormal Doppler results were used only to determine the frequency of fetal testing. Biophysical profile testing was performed semiweekly on all patients. Patients with absent or reversed end-diastolic flow were admitted for daily testing. The following criteria were used as indications for delivery: (1) worsening maternal condition, (2) oligohydramnios, (3) intrauterine growth retardation with lung maturity, and (4) biophysical profile score less than or equal to 4. Fifty-one patients (7%) had abnormal Doppler blood flow velocity studies. When the study population was compared with the control population at the time of delivery, there were no differences in umbilical artery pH, Apgar score, or incidence of intrauterine growth retardation. However, study patients were delivered at a significantly lower gestational age and lower birth weight and experienced a higher likelihood of neonatal intensive care unit admission. When study patients with documented end-diastolic flow were compared with study patients with no end-diastolic flow, there were no differences in umbilical artery pH, Apgar score, or incidence of intrauterine growth retardation. However, fetuses with no end-diastolic flow had a significantly shorter test-to-delivery interval, lower gestational age, lower birth weight, and more neonatal intensive care unit admissions. There were no perinatal deaths among the study patients. The range of systolic/diastolic ratios for the five patients who failed to follow our protocol for intensive maternal-fetal surveillance was 4.3 to infinity; all experienced fetal death within 18 days. These results suggest that immediate delivery of the fetus with diminished end-diastolic flow may not be mandatory. The combined use of fetal biophysical testing and commonly used criteria for delivery results in acceptable fetal outcome and prolongation of gestational age.