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OBJECTIVE:Our purpose was to evaluate Doppler-detectable differences in the fetal circulation of discordant twins with a growth defect resulting from either placental insufficiency or twin-to-twin transfusion syndrome. STUDY DESIGN:Serial weekly Doppler recordings were performed for at least 3 weeks preceding delivery in 15 pairs of dichorionic twins (group A) in which the smaller twin had fetal distress (i.e., antepartum fetal heart rate late decelerations) and in 10 pairs of diamniotic and monochorionic twins (group B) in which the diagnosis of twin-to-twin transfusion syndrome was confirmed postnatally. Doppler recordings were obtained from umbilical artery, descending aorta, and middle cerebral artery, and the pulsatility index values were calculated. Furthermore, peak velocity from cardiac outflow tract and the percent of reverse flow in the inferior vena cava were calculated. For all these index values the intertwin differences (Δ value) were calculated by subtracting the values obtained in the larger twin with those of the smaller twin. RESULTS:In group A significant changes of Δ values were evidenced for all the parameters tested. In particular, Δ values of pulsatility index from the umbilical artery and descending aorta progressively increased approaching the occurrence of late decelerations, whereas the Δ value for the middle cerebral artery reached a nadir 2 weeks before delivery. Similarly, Δ values of peak velocity from outflow tracts significantly decreased, whereas those of the percent reverse flow in the inferior vena cava increased during the time considered. In group B fetuses no significant intertwin differences in pulsatility index values were evidenced in the vessels investigated, resulting in absence of modifications in Δ values during the time interval considered. Moreover, significant changes were found in Δ values of both the peak velocity from the outflow tract and the percent of reverse flow in the inferior vena cava. However, these changes were limited to the last recording, where the former Δ value increased and the latter decreased. CONCLUSIONS:Serial Doppler recordings may show hemodynamic changes in the fetal circulation of discordant twins. Different trends occur according to the underlying pathophysiologic mechanisms of the growth defect. The knowledge of these temporal changes may be useful in the management of such fetuses. (AMJ OBSTETGYNECOL1994;170:1321-7.)

To compare uterine artery resistance index values in twin and singleton pregnancies, to examine eventual modifications of these values in twin pregnancies complicated by gestational hypertension and preeclampsia, and to determine whether resistance index values in twin pregnancies could predict the development of gestational hypertension and preeclampsia.

Intrauterine growth retardation continues to be one of the major problems in obstetrics and still greatly contributes to perinatal mortality and morbidity. This paper reviews the role of Doppler ultrasonography in the antenatal assessment of fetuses with intrauterine growth retardation. Recent developments in this field are described with particular emphasis on the pathophysiologic background of the hemodynamic modification of fetuses with intrauterine growth retardation. Doppler ultrasonography allows the prediction of the development of intrauterine growth retardation in selected populations and the identification among a population of small-for-gestational-age fetuses, those really at risk of unfavorable outcome. Finally, the modifications occurring after the establishment of the growth retardation with the progression of fetal deterioration are described in an attempt to clarify the natural history of this condition. To this end, the longitudinal changes of Doppler indices of placental vessels, fetal arterial vessels, fetal heart, and venous circulation are described, and their complex interrelationship is analyzed. The knowledge of these mechanisms may be useful in deciding the timing of delivery.

The objective of this study was to examine the acid-base status in blood obtained at cordocentesis in growth-retarded fetuses with absent end-diastolic velocity in the umbilical artery and divided according to the presence or absence of pulsations in the umbilical vein. Twenty-six growth-retarded fetuses free from structural and chromosomal abnormalities were considered for this study. All the fetuses had absent end-diastolic velocity in the umbilical artery associated in 11 cases (42.3%) with pulsations in the umbilical vein. Gas analysis of fetal blood obtained by cordocentesis was performed immediately after the Doppler recordings. Hypoxemia, acidemia and hypercapnia were defined respectively as the presence of pH or pO2 values 2 standard deviations below the normal mean for gestation and of pCO2 values 2 standard deviations above the normal mean for gestation. Fetuses with umbilical vein pulsations had lower values of pH (p < 0.001) and pO2 (p < 0.05) and higher values of pCO2 (p < 0.001) when compared to those without pulsations. All fetuses with pulsations were hypoxemic and hypercapnic and the incidence of acidemia was 90.9%. Fetuses with continuous blood flow in the umbilical vein, although frequently hypoxemic (80%), have pC02 and pH values within the normal range in 40 and 52.3% of the cases, respectively. In conclusion, in fetuses with absent end-diastolic velocity in the umbilical artery the presence of umbilical vein pulsations identifies a subgroup of fetuses with a more severe compromise of acid-base status. This may be useful in the selection of the timing of delivery of such fetuses.

The objective of this study was to analyze the effects of cordocentesis on velocity waveforms recorded from the inferior vena cava and to evaluate differences, if any, in the hemodynamic response between normally grown and growth-retarded fetuses. Twenty-five normally grown fetuses and 20 growth-retarded fetuses were considered for this study. This latter group was characterized by abnormal Doppler indices in the umbilical artery and the middle cerebral artery suggestive of uteroplacental insufficiency as the causative factor of the impaired growth. Flow velocity waveforms were measured from the inferior vena cava immediately before and after cordocentesis and the % reverse flow during atrial contraction calculated. In normally grown fetuses the % reverse flow values did not vary significantly after cordocentesis, while in growth-retarded fetuses this index increased significantly after the procedure (p < 0.001). Furthermore, the amplitude of this increase was inversely related to pH levels in umbilical vein (p = 0.004). In conclusion, in growth-retarded fetuses cordocentesis induces an increase of % reverse flow in the inferior vena cava, while no modifications occur in normally grown fetuses. This suggests the presence in growth-retarded fetuses of an impaired cardiac adaptive mechanism to cordocentesis that may explain the higher incidence of complications occurring in such fetuses.

In order to assess whether maternal hyperoxygenation induces modifications of Doppler-measured velocity waveforms across atrioventricular valves, 15 healthy and 15 growth-retarded fetuses were studied in basal conditions and during the maternal administration of 60% humidified oxygen. Recordings were performed at 5-min intervals before, during and after maternal oxygen administration. In basal conditions, growth-retarded fetuses exhibited significantly lower ratios between the velocities during early passive ventricular filling and active ventricular filling (E/A ratio) at the level of both mitral and tricuspid valves when compared to healthy fetuses. Furthermore in healthy fetuses the velocity time integral across the tricuspid valve always slightly exceeded that across the mitral valve, whilst growth-retarded fetuses showed an inversed ratio between these velocities. During oxygen administration no changes were found between the two groups of fetuses with regard to the E/A ratios. Similarly the velocity time integrals were unaffected by oxygen administration in the healthy fetuses. Besides growth-retarded fetuses exhibited significant temporary modifications during oxygen administration as expressed by an increase in the velocity time integral across the mitral valve associated with a decrease of that across the tricuspid. These changes result in an inversion of the ratio between transtricuspid and transmitral velocity time integrals reaching values similar to those of healthy fetuses. Short-term oxygen administration affects the intracardiac flow redistribution present in growth-retarded fetuses bringing it to a pattern similar to that of healthy fetuses whereas the E/A ratios were not affected by the treatment.

We previously demonstrated a prognostic significance of maternal oxygen test in predicting imminent fetal distress. The purpose of this study was to investigate eventual other factors related to the length of the time interval elapsing between the Doppler diagnosis of brain sparing effect and abnormal fetal heart rate patterns. To this end we considered 101 growth-retarded fetuses free of structural and chromosomal abnormalities with a ratio between the pulsatility indices of umbilical and middle cerebral artery above the 95th centile in presence of a normal fetal heart rate pattern. The factors, other than the oxygen test, analyzed for a potential influence on this time interval were gestational age, presence of hypertension or preeclampsia, amniotic fluid index, severity of growth retardation (centile of the ultrasonographic estimated fetal weight) and 9 different Doppler indices calculated from extra- and intracardiac districts. Statistical actuarial methods were used to determine the effect of these prognostic factors on the duration of this time interval. The occurrence of abnormal fetal heart rate patterns (antepartum late heart rate decelerations) was used as censoring variable. The time interval between the entry in the study and delivery ranged from 1 to 39 days. Indications for delivery were fetal distress in 53 fetuses (52.4%) and different maternal or fetal complications in the remaining 48 fetuses. Multivariate analysis showed that the factors that independently affect the time interval between Doppler abnormalities and development of abnormal fetal heart rate patterns are the oxygen test (p ≤ 0.001), the percentage of reverse flow in inferior vena cava (p ≤ 0.001), gestational age (p ≤ 0.01) and the presence of hypertension (p ≤ 0.05). The knowledge of these prognostic factors may be useful in the clinical management of growth-retarded fetuses.