A comparison of fetal heart rate monitoring and umbilical artery waveforms in the recognition of fetal compromise

Nanotechnological approaches for the treatment of placental dysfunction: recent trends and future perspectives

The transitory placenta develops during pregnancy and mediates the blood flow between the mother and the developing baby. Placental dysfunction, including but not limited to placenta accreta spectrum, fetal growth restriction, preeclampsia and gestational trophoblastic disease, arises from abnormal placental development and can result in significant adverse maternal and fetal health outcomes. Unfortunately, there is a lack of treatment alternatives for these disorders. Nanocarriers offer versatility, including extended circulation, organ-specific targeting and intracellular transport, finely tuning therapeutic placental interactions. This thorough review explores nanotechnological strategies for addressing placental disorders, encompassing dysfunction insights, potential drug-delivery targets and recent strides in placenta-targeted nanoparticle (NP) therapies, instilling hope for effective placental malfunction treatment.

A review of fetal cardiac monitoring, with a focus on low- and middle-income countries

There is limited evidence regarding the utility of fetal monitoring during pregnancy, particularly during labor and delivery. Developed countries rely on consensus ‘best practices’ of obstetrics and gynecology professional societies to guide their protocols and policies. Protocols are often driven by the desire to be as safe as possible and avoid litigation, regardless of the cost of downstream treatment. In high-resource settings, there may be a justification for this approach. In low-resource settings, in particular, interventions can be costly and lead to adverse outcomes in subsequent pregnancies. Therefore, it is essential to consider the evidence and cost of different fetal monitoring approaches, particularly in the context of treatment and care in low-to-middle income countries.

This article reviews the standard methods used for fetal monitoring, with particular emphasis on fetal cardiac assessment, which is a reliable indicator of fetal well-being. An overview of fetal monitoring practices in low-to-middle income counties, including perinatal care access challenges, is also presented. Finally, an overview of how mobile technology may help reduce barriers to perinatal care access in low-resource settings is provided.

Estimation of the Doppler ultrasound umbilical maximal waveform envelope: II. Prediction of fetal distress

Blood flow variables obtained via Doppler ultrasound (US) waveform estimation have been investigated for prediction of fetal distress. The umbilical flow was assessed using a number of waveform summary statistics in addition to the currently used resistance indices. We examined the relationship between umbilical artery waveform patterns and intrauterine growth restriction, preterm delivery and hypertensive disorders. To enhance prediction, we defined waveform skewness profiles based on pivotal points of the umbilical waveform that appeared to be related to the incidence of preterm delivery and that facilitated construction of IUGR prediction models. The data comprised 204 unselected pregnancies with the umbilical artery images recorded at 18 pregnancy weeks. The sample was divided into 114 pregnancies used to estimate model parameters and 90 pregnancies to validate the model. Logistic prediction models for detection of abnormal velocity waveforms associated with intrauterine growth restriction were derived, based on the waveform information. The estimated model sensitivity and specificity on the training data were 74% and 84%, respectively. Validation of the model on independent data yielded a sensitivity of 57% and specificity of 84%. The logistic IUGR prediction model appears to have significant predictive ability and potential for clinical use, even at this early gestational age. Our data suggest that prediction of IUGR at 18 pregnancy weeks can be much improved when the waveform shape is captured with a number of summary statistics in addition to resistance indices.

Influence of acupuncture on Doppler ultrasound in pregnant women

OBJECTIVE

To evaluate the influence of acupuncture on the blood flow in the umbilical artery (UA), fetal aorta and uterine artery and on the fetal heart rate using two different acupuncture points (SP-6 (Sanyinjiao) and LI-4 (Hegu)).

METHODS

In group A (n = 50), measurements (Doppler ultrasound and fetal heart rate) were performed at term after an uneventful pregnancy (#1) followed by acupuncture treatment using the acupuncture-point SP-6 bilaterally. The treatment time lasted 15 min after which the next measurement (#2) was carried out. The needles were then inserted into the LI-4 acupuncture point for a further 15 min. A third measurement at the end of acupuncture treatment (#3) completed the session. In group B (n = 25), measurements were made before (#1) and after (#4) acupuncture at LI-4 acupuncture points only.

RESULTS

In group A, the mean systolic/diastolic (S/D) ratios of UA #1, UA #2 and UA #3 were 2.45, 2.38 and 2.22, respectively (P = 0.0012). The difference in mean S/D ratios between UA #1 and UA #3 as well as that between UA #2 and UA#3 were statistically significant (P = 0.0002 and P = 0.008, respectively). There was no difference between the mean S/D ratios of the uterine artery and between the mean resistance indices of the fetal aorta. In group B, the only significant difference between measurements following acupuncture treatment was in fetal heart rate (139 vs. 143 bpm, P = 0.02).

CONCLUSION

Our study indicates a positive influence of acupuncture treatment on umbilical artery waveforms when using a combination of SP-6 (Sanyinjiao) and LI-4 (Hegu) acupuncture points. Acupuncture performed at these sites either individually or in combination does not seem to affect blood flow in the fetal aorta or uterine artery.

Nicotine patch use in pregnant smokers: nicotine and cotinine levels and fetal effects

OBJECTIVE

The aims of this study were (1) to determine whether nicotine patch therapy for pregnant women smokers acutely compromises fetal well-being and (2) to determine the serum and urine nicotine and cotinine levels in pregnant women while smoking, while abstinent from smoking, and while receiving nicotine patch therapy compared with levels in a historical control group of nonpregnant women smokers who abstained from smoking while receiving comparable doses of nicotine patch therapy.

STUDY DESIGN

Pregnant cigarette smokers (n = 21) aged >/=18 years whose fetuses were beyond 24 weeks' gestational age were recruited for this 1-sample, repeated-measures study. Serial measurements of the mother and fetus were made at baseline while the mother was smoking, while abstaining from smoking, and while using nicotine patch therapy for 4 days in a special care hospital unit. Nonpregnant women smokers of similar age were used for comparison. Morning and afternoon serum and 24-hour urine levels of nicotine and cotinine were obtained during hospitalization. Indicators of fetal well-being assessed were fetal heart rate and reactivity, systolic/diastolic ratio of blood flow in the umbilical artery, and fetal activity seen on ultrasonography and quantitated as biophysical profiles.

RESULTS

No evidence of fetal compromise was seen during the inpatient phase while nicotine patch therapy was administered. Steady state (inpatient day 4) serum levels of nicotine were similar to smoking levels and to those seen in historical control subjects (ie, nonpregnant women of child-bearing age who were abstinent from smoking and who used the same nicotine patch). Morning serum cotinine levels were significantly higher (P =.038) in the nonpregnant subjects than in the pregnant subjects, whereas afternoon levels were not significantly different. Steady state urinary levels of nicotine and cotinine were also not significantly different in pregnant versus nonpregnant patients. On inpatient days 2, 3, and 4, when the women were not smoking and were wearing the nicotine patch, the morning fetal heart rates were significantly reduced relative to baseline when the subjects were smoking.

CONCLUSIONS

Nicotine patch therapy was not found to be associated with indications of fetal compromise during the in-hospital phase of nicotine patch therapy in pregnant smokers who were abstaining. Although not conclusive because of the small sample sizes, serum nicotine levels (morning and afternoon) appear similar in pregnant and nonpregnant subjects and similar for both groups when smoking (baseline) as compared to the steady state of nicotine patch use.

Antepartum testing

Among the methods of antepartum testing in use today, the nonprovocative tests (NST, BPP, MBPP) are safe and effective for use in ambulatory settings. Outpatient or office utilization of the CST is limited by the need for intravenous access (when oxytocin is used) and by the potential for uterine hyperstimulation and resultant acute FHR abnormalities. Regardless of the method of testing used, large studies have confirmed that the fetal death rate among patients undergoing antepartum testing is significantly lower than that in the general, untested population. This is a particularly encouraging observation in view of the fact that antepartum testing is used almost exclusively in complicated pregnancies at highest risk for poor outcome. In the future, protocols using adjunctive testing methods (fetal movement counting, fetal movement profile, Doppler velocimetry) in combination with standard methods (CST, NST, BPP, MBPP) may further reduce the incidence of fetal death in high-risk populations. At present, the beneficial effects of antepartum testing have created a situation in which the likelihood of fetal death in high-risk, tested populations is lower than that in low-risk, untested populations. This paradox will force us to consider the option of routine antepartum testing in all pregnancies.

Amniotic fluid and the umbilical cord: the fetal milieu and lifeline

Amniotic fluid volume should be routinely assessed in every second and third trimester case. A review of amniotic fluid physiology and techniques for ultrasound evaluation of fluid volume is presented. The causes and significance of oligohydramnios and polyhydramnios are stressed. Umbilical cord abnormalities are often incidently observed at the time of amniotic fluid evaluation. The clinical significance of some common umbilical cord abnormalities such as a two-vessel cord and nuchal cord are discussed. Other, more uncommon entities such as cord mass lesions are also reviewed. Finally, the role of cord Doppler interrogation in determining fetal well-being is discussed.

Randomised controlled trial of cardiotocography versus umbilical artery Doppler in the management of small for gestational age fetuses

OBJECTIVE

To compare the impact on use of resources in the management of small for gestational age babies using Doppler ultrasound versus cardiotocography.

DESIGN

A randomised controlled trial.

SETTING

A large district general hospital delivering 5500 to 6000 infants each year, 30% to 35% of which are to women of Pakistani origin.

POPULATION

One hundred and fifty women delivered of small for gestational age infants.

MAIN OUTCOME MEASURES

Primary outcome measures were length of hospital inpatient stay and induction of labour rates. Secondary outcome measures included caesarean section rates and length of stay on neonatal unit.

RESULTS

The use of Doppler reduced average hospital inpatient stay from 2.5 days to 1.1 days, compared with cardiotocography (P = 0.036). There was no effect on induction of labour rates or caesarean section rates. There was no significant difference in length of stay on the neonatal unit (P = 0.33). There was a reduction in monitoring frequency and fewer hospital antenatal clinic visits.

CONCLUSION

The use of Doppler ultrasound to manage small for gestational age infants reduces the use of resources, compared with cardiotocography.

Effects of hypoglycaemia on fetal heart activity and umbilical artery Doppler velocity waveforms in pregnant women with insulin-dependent diabetes mellitus

OBJECTIVE

To study the effect of induced hypoglycaemia on fetal wellbeing as indicated by fetal heart rate and umbilical artery flow velocity waveforms.

DESIGN

A prospective experimental investigation.

SETTING

High risk pregnancy unit and diabetes research unit at Karolinska Institutet, Danderyd Hospital, a university affiliated hospital.

PARTICIPANTS

Ten women with insulin-dependent diabetes mellitus in the third trimester of pregnancy.

INTERVENTIONS

The fetal heart rate, the blood flow velocity waveforms in the umbilical artery and the maternal catecholamine levels were investigated during a 150-minute hyperinsulinaemic hypoglycaemic clamp with induction and maintenance of an arterial blood glucose level of about 2.2 mmol/l.

MAIN OUTCOME MEASURES

1. Fetal: changes of fetal heart rate pattern and pulsatility index of the umbilical artery flow velocity waveforms. 2. Maternal: levels of plasma adrenaline and plasma noradrenaline.

RESULTS

Maternal hypoglycaemia was associated with an increase in frequency and amplitude of fetal heart rate accelerations, a slight decrease in the pulsatility index of the umbilical artery and a rise in the maternal catecholamine levels.

CONCLUSIONS

We speculate that the increased number of fetal heart rate accelerations reflects an increased sympathico-adrenal activity during the hypoglycaemia clamp. No potentially harmful effects on the fetus were observed in the fetal heart rate or in the umbilical artery Doppler waveform analysis during hypoglycaemia.

Umbilical artery Doppler velocimetry compared with fetal heart rate monitoring as a labor admission test

A total of 155 patients admitted in early labor to the delivery unit of the University of Hong Kong were recruited into a study comparing the value of umbilical artery Doppler velocimetry and fetal heart rate (FHR) monitoring in early labor as an admission test. FHR monitoring for 30 min was recorded on admission, and umbilical A/B ratio was simultaneously performed. The FHR tracing was scored according to the Lyons score by a third independent observer after delivery. Outcome variables studied included small for gestational age (SGA), intrapartum FHR abnormalities, operative deliveries for fetal distress, umbilical cord pH, Apgar scores, admission into the special care baby unit, and a combination of the variables. It was found that at cut-off values of Lyons score < 7 and umbilical A/B ratio > 2.6 at term, about 19% of cases were abnormal for either tests, with only a few cases of overlap. Umbilical A/B ratio was found to be significantly correlated with SGA. The sensitivity and positive predictive values were, however, low. Both tests were relatively poor predictors for most of the outcome variables studied. Interestingly, FHR monitoring did not seem to have any advantage over Doppler velocimetry as a labor admission test. Further larger scale studies to evaluate their usefulness in medium and low risk populations are indicated.

The predictive value of Doppler flow velocity waveforms in the development of abnormal fetal heart rate traces in intrauterine growth retardation: a longitudinal study

In a longitudinal, blinded study design the predictive value of Doppler velocimetry for the development of an abnormal fetal heart rate trace was assessed in 42 cases of intrauterine growth retardation. Doppler velocity waveform recordings were obtained at 2- to 3-day intervals and characterized by the standard deviation score of the pulsatility index in the umbilical artery and internal carotid artery, and the peak systolic and time-averaged velocity in the ascending aorta and pulmonary artery. Twenty-seven patients did not display an abnormal fetal heart rate trace on the day of entry into the study. During follow-up of these patients, the pulsatility index in the umbilical artery and internal carotid artery were the most predictive parameters for the development of an abnormal fetal heart rate trace. The resulting prognostic index was found to have an acceptable discriminative power in the prediction of abnormal fetal heart rate traces as established in a second group of growth-retarded fetuses.

Screening for fetal distress in labour using the umbilical artery blood velocity waveform

OBJECTIVE

To investigate the potential value of umbilical artery blood velocity wave-form measurement as a screening test for intrapartum fetal distress on admission to the labour ward.

DESIGN

Prospective study drawn from the local population of pregnant women.

SETTING

The labour ward of the Princess Anne Hospital, Southampton, UK.

SUBJECTS

334 women with singleton pregnancies of at least 37 weeks gestation.

MAIN OUTCOME MEASURE

Emergency caesarean section for fetal distress.

RESULTS

There was a twelve-fold increase in the rate of emergency caesarean section for fetal distress (95% Confidence Interval (CI), 4.9-29) among women with a systolic/diastolic (S/D) ratio > or = 3.0, when compared to those with an S/D ratio of < 3.0 (P < 0.00001). Measurement of the umbilical artery blood velocity waveform compared favourably with admission cardiotocography.

CONCLUSIONS

Umbilical artery blood velocity waveform analysis may be used to screen for fetal distress in labour and appears to be particularly sensitive to problems of placental origin. However, it is not likely to confer benefit in labour wards whose fetal heart rate monitoring policy is determined by pregnancy risk factors and admission cardiotocography.

Comparison of umbilical-artery velocimetry and cardiotocography for surveillance of small-for-gestational-age fetuses

Intrauterine growth retardation is associated with an increased risk of fetal asphyxia as well as greater perinatal morbidity and mortality. Ultrasound fetometry enables detection of fetuses that are small for gestational age. Doppler velocimetry of the umbilical artery has good predictive ability for fetal distress, but it is not yet clear whether it could replace cardiotocography in antenatal surveillance of small-for-gestational-age fetuses. We have done a randomised comparison of the two methods. At four obstetric departments in Sweden, women with fetuses found to be small on ultrasound examination at 31 completed weeks of pregnancy or later were randomly assigned to antenatal surveillance with either doppler velocimetry (doppler; 214) or cardiotocography (CTG; 212). Pregnancies in the doppler group were managed according to a protocol based on blood-flow classes deriving from the semiquantitative evaluation of umbilical-artery velocity waveforms; unless the pregnancy was complicated by any other disorder, no antenatal cardiotocography was done. By comparison with the CTG group, the doppler group had fewer monitoring occasions (mean 4.1 [SD 3.1] vs 8.2 [6.2], p < 0.01), antenatal hospital admissions (68 [31.3%] vs 97 [45.8%], p < 0.01), inductions of labour (22 [10.3%] vs 46 [21.7%], p < 0.01), emergency caesarean sections for fetal distress (11 [5.1] vs 30 [14.2%], p < 0.01), and admissions to neonatal intensive care (76 [35.5%] vs 92 [43.4%], p = 0.10). The groups did not differ in gestational age at birth, birthweight, Apgar scores, or total number of caesarean deliveries. Umbilical-artery doppler velocimetry of small-for-gestational-age fetuses allows antenatal monitoring and obstetric interventions to be aimed more precisely than does cardiotocography.

Doppler velocimetry in twin pregnancy

The flow velocity waveform profile in the umbilical artery was measured in 50 pairs of twins during the last week before birth. A significant association was found between high resistance indicies and occurrence of late fetal heart rate decelerations; the higher the resistance, the more frequent the decelerations. Further, the connection between high resistance in the circulation of the umbilical artery and low birth weight was confirmed. Flow velocity measurements in the umbilical artery seem to be a valuable tool in identifying twin fetuses suffering from placental insufficiency.

The role of Doppler technology in the evaluation of fetal hypoxia

Failing intrauterine support to the fetus can lead to intrauterine growth retardation (IUGR) and hypoxia and it is associated with a high risk of perinatal morbidity and mortality. The main effects of moderate to severe hypoxia on the fetus are different degrees of blood flow redistribution and reduction of oxygen consumption to maintain oxygen delivery to the central organs at the expenses of peripheral organs. The redistribution results in a 'brain sparing' effect. Recently, a Doppler ultrasonic technology (continuous wave, pulsed wave and colour flow imaging) has been developed for the non invasive measurement of flow. Doppler velocimetry detects the flow velocity waveform (FVW) which reflects the cardiac output, the vascular compliance and the resistance to the flow in a defined point of the vessel. Velocity waveform indices or even simpler criteria, such as the presence or absence of diastolic flow or flow reverse during diastole, have been applied to a number of fetal vessels. A significant relationship exists between blood oxygen, systemic lactic acidosis (determined by cordocentesis) and increase PI values in umbilical artery (UA), thoracic aorta (TA) and renal artery (RA). Moreover, in experimental animals during steady state hypoxia, several cardiovascular parameters are affected (heart rate/cardiac output decreases and blood pressure increases) while placental flow don't show a significant variation thus suggesting a raise in placental vascular resistance. Redistribution of the flow may be reliably evaluated by the cerebroplacental ratio (i.e. ratio between PI of MCA and PI of UA, c/p).(ABSTRACT TRUNCATED AT 250 WORDS)

Prediction of fetal outcome in small for gestational age fetuses: comparison of Doppler measurements obtained from different fetal vessels

Blood flow velocity waveforms were recorded from different vascular districts including umbilical artery, descending aorta, renal artery, internal carotid artery and middle cerebral artery in a population of 120 small for gestational age fetuses free from structural and chromosomal abnormalities. The pulsatility index from each vessel as well as the ratios between the pulsatility indices from peripheral and cerebral vessels were calculated and related to perinatal outcome. The pulsatility index of middle cerebral artery resulted the most efficient measurement to predict the development of perinatal adverse outcome when each vessel was considered singularly, however, better results were achieved when the ratios between pulsatility indices were related to perinatal outcome; this is mot evident for the ratio between the pulsatility indices of umbilical artery and middle cerebral artery. Our results suggest the usefulness of this ratio in differentiating small for gestational age fetuses at risk of unfavorable outcome.

Doppler umbilical velocimetry in women with polydrug abuse including cocaine

Doppler umbilical artery velocimetry was performed in 40 chemically dependent women. The mean S/D ratio was 2.7 with 15/66 values greater than or equal to 3.0. No cases of absent or reverse end-diastolic flow were noted. The mean S/D ratio in women with positive toxicologies for cocaine use was not statistically elevated compared to women with negative screens (2.8 versus 2.7, P = 0.51). In this study an S/D ratio greater than or equal to 3.0 had a sensitivity of 40% for identifying intrauterine growth retardation with a positive predictive value of 20%.

Placental morphology in relation to umbilical artery blood velocity waveforms

The association between umbilical artery flow velocity waveforms, placental morphology and arterial vascular pattern was investigated in 30 pregnant women at risk for intra-uterine growth retardation. The blood velocity waveform was assessed in the umbilical arteries with pulsed Doppler ultrasound. Placentas from fetuses with an end-diastolic zero flow were small and thick with an extrachorial configuration, marginal cord insertion, magistral or mixed allantochorial vessel pattern and few cotyledons. The incidence and the extension of gross lesions were slightly increased in these placentas compared to placentas from fetuses with a normal S/D ratio (peak systolic velocity/minimum diastolic velocity). Placentas from fetuses with an increased S/D ratio (greater than +2SD) were large and thin with a high maximum diameter/maximum thickness ratio. Heavily smoking mothers were overrepresented in the group, with an increased S/D ratio and corresponding SGA infants. End-diastolic zero flow in the umbilical artery was strongly correlated with placental developmental abnormalities.

Absent or reversed end diastolic flow velocity in the umbilical artery and necrotising enterocolitis

Absent or reversed end diastolic flow (AREDF) velocities in the umbilical artery were identified in 25 high risk pregnancies. In six pregnancies the fetus was abnormal and all but one of these ended in perinatal death. Of the 19 morphologically normal fetuses, three died in utero and there were four neonatal or infant deaths. The mortality rate was 48% for all pregnancies and 37% for those with morphologically normal fetuses. There was a highly significant increased risk for the development of necrotising enterocolitis in these morphologically normal fetuses with AREDF (53%) compared with controls (6%) who did have umbilical artery end diastolic flow velocities in fetal life. There were no significant differences between the matched pairs for parameters of neonatal outcome chosen to reflect neonatal morbidity. These findings demonstrate the close association between AREDF and necrotising enterocolitis that appears to be independent of other variables such as degree of growth retardation, prematurity, and perinatal asphyxia.

Comparative efficacy of umbilical arterial Doppler indices for predicting adverse perinatal outcome

A variety of descriptor indices for the umbilical arterial Doppler waveform are currently in use for predicting perinatal outcome. However, there is a paucity of data regarding the relative diagnostic merits of these indices. We addressed this issue in a prospective, blind study in which the diagnostic efficacy of the following Doppler indices was compared: resistance index, systolic/diastolic ratio, pulsatility index, and diastolic average ratio. The analytic technique consisted of the receiver operating characteristic method, which evaluates a test's ability to discriminate a diseased from a healthy population. The patient population consisted of 350 pregnant patients with gestational ages of 34 to 36 weeks. A continuous-wave Doppler device with a 4 MHz transducer was used to investigate the umbilical vessels. The test was performed only once in each patient. The abnormal outcome parameters included small for gestational age (less than 10th percentile), Apgar score less than 7 at 5 minutes, fetal distress (late and severe variable decelerations, absent variability, fetal scalp pH less than 7.20), umbilical cord arterial pH less than 7.10, presence of thick meconium, and admission to neonatal intensive care unit (greater than 48 hours). The results showed that the resistance index had the best discriminatory ability when compared with other Doppler indices: the systolic/diastolic ratio (p less than 0.05), the pulsatility index (p less than 0.001), and the diastolic/average ratio (p less than 0.05). It is concluded that of the various Doppler indices assessed in this investigation, the resistance index offers the best diagnostic efficacy in predicting perinatal compromise.

Fetal umbilical artery velocity waveforms and subsequent neonatal outcome

Flow velocity waveforms (FVWs) from the fetal umbilical artery were recorded from 2178 pregnant women over a 6-year period. All of them had an obstetric factor indicating increased risk of fetal compromise. A total of 6749 studies was recorded. The systolic diastolic (AB) ratio was measured and classified as normal (less than 95th centile), elevated (95-99th centile), high (greater than 99th centile) or extreme (absent diastolic flow). The results of these studies have been related to subsequent fetal and neonatal outcome. An abnormal umbilical artery FVW was associated with shorter gestation and infants with lower birthweight, shorter length and lower ponderal index. There was a highly significant association between an abnormal FVW and the birth of an infant small for gestational age. The significance of the association increased with the increased abnormality of the umbilical artery FVW and this was independent of gestational age. Preterm infants associated with high or extreme AB ratios spent twice as long in the neonatal nursery than those with normal AB ratios. Analysis of 794 pregnancies studies serially indicated that an abnormal FVW in which the AB ratio was increasing, in contrast to a decreasing AB ratio, predicted a poor outcome for both size at birth and duration of neonatal intensive care. We conclude that in high risk pregnancy Doppler umbilical artery FVW studies predict the most compromised fetuses in terms of growth retardation and requirements for neonatal intensive care.

The value of cordocentesis in management of patients with severe preeclampsia

Severe preeclampsia affects placental function and causes fetal compromise. It is necessary to deliver the fetus at an appropriate time in order to minimize fetal mortality and morbidity. Cordocentesis was performed in 9 patients with severe preeclampsia (group 1) and 10 patients with other pregnancy complications (group 2). Intrauterine growth retardation occurred in 5 patients in group 1 and in only one patient in group 2. Blood gas parameters including pH, pO2 and O2 saturation were significantly lower for group 1, while pCO2 was significantly higher, as compared to group 2. For patients in group 1, non-invasive fetal surveillance successfully identified 5 patients with fetal compromise, who required immediate termination of pregnancy. All 5 of these patients had abnormal fetal blood gas analyses by cordocentesis. Fetal blood gas analysis was abnormal in 2 additional fetuses among the remaining 4 patients who exhibited normal findings by non-invasive methods of fetal surveillance. These results suggest that cordocentesis is useful in identifying fetal compromise (fetal hypoxia/acidosis) prior to the onset of labor in high-risk patients, such as preeclampsia associated with intrauterine growth retardation.

Doppler umbilical artery velocimetry in pregnancies complicated by intrahepatic cholestasis

Doppler umbilical velocimetry is a useful clinical tool for antepartum fetal surveillance of pregnancies at risk of fetal compromise. Intrahepatic cholestasis of pregnancy is associated with an increased incidence of fetal death, which might due to the toxic effect of elevated maternal serum concentrations of bile acids. To study a possible effect of the concentration of bile acids on the umbilical circulation we performed pulse-wave Doppler velocimetry of the umbilical artery in 15 patients with intrahepatic cholestasis between 34 and 38 weeks of gestation. The findings were compared to the Doppler flow velocities of the umbilical artery of 129 normal pregnancies. Peak-systolic (A) and end-diastolic (B) velocities of two to three cardiac cycles were measured by electronic calipers and the Pourcelot (PR)-index (PR = (A - B)(A)) was calculated. Two of 29 Doppler measurements in patients with intrahepatic cholestasis were above two standard deviations (2 SD) of the values in normal pregnancies. No significant correlation was found between Doppler flow velocities and serum levels of bile acids (r = 0.20) or the levels of alanine aminotransferase (ALAT) (r = -0.05). The mean level of bile acids was 24 mumol/l with a maximum of 98 mumol/l. The mean level of ALAT was 165 IU/l with a maximum of 576 IU/l. Since even high levels of bile acids do not influence umbilical circulation, Doppler investigations of the umbilical artery seem to be of little value in studying the disease-specific risk of fetal compromise in pregnancies complicated by intrahepatic cholestasis.

Effects of acute hypoxemia on umbilical arterial Doppler indices in a fetal ovine model

Changes in umbilical arterial Doppler waveform in response to acute maternal hypoxemia were assessed in a chronic ovine model. Maternal heart rate, blood gases, fetal heart rate and umbilical arterial Doppler indices measured at baseline conditions and during periods of maternal hypoxemia were compared. The indices measured were systolic-diastolic ratio (S/D), pulsatility index (PI) and resistance index (RI). Fetal heart rate decreased (less than 80 beats/min) and umbilical arterial Doppler indices increased (P less than 0.001) during the periods of hypoxemia. Furthermore, the Doppler indices were highly but negatively correlated with alterations in the fetal heart rate (FHR) (P less than 0.001). Analysis of the Doppler waveform phase intervals revealed nearly constant systolic intervals while diastolic intervals varied inversely with the heart rate alterations. Moreover, the umbilical arterial Doppler indices, when corrected for FHR changes, were relatively unchanged from baseline measurements. This study indicates that maternal hypoxemia induced changes in the umbilical arterial Doppler indices may be primarily attributable to the changes in FHR.

Abnormal velocity waveforms of the umbilical artery in growth retarded fetuses: relationship to antepartum late heart rate decelerations and outcome

In 70 intrauterine growth-retarded (IUGR) fetuses with antepartum late heart rate decelerations recordings of velocity waveforms of the umbilical artery were made with Doppler ultrasound and calculated as pulsatility indexes (PI). In 29 of these fetuses longitudinal recordings were made. Abnormal PIs preceded the occurrence of late heart rate decelerations in 27 (93%) of the 29 fetuses. The median duration of the interval between the first abnormal PI and the first appearance of antenatal heart rate decelerations was 17 days (range 0-60 days). This wide range can mainly be attributed to the gestational age at which the first abnormal velocity wave-form was recorded; during early gestation the interval was much longer than later in pregnancy. Absent end-diastolic velocity (AEDV) was found in 17 of the 29 fetuses (59%) and preceded the occurrence of decelerations with a median interval of 12 days. In the total group, 4 of the 70 IUGR fetuses with antepartum decelerations had a normal velocity waveform of the umbilical artery. Fetuses with AEDV (n = 45) were more severely growth retarded and were delivered at an earlier gestational age than those with end-diastolic velocity (n = 25). Also perinatal mortality and morbidity were higher in the group with AEDV. Yet, when fetuses were matched for gestational age and birth weight no differences in perinatal outcome were found in the groups with and without end-diastolic velocity.

Doppler velocimetry of the umbilical and uteroplacental circulation: a critical review

During the past 8 years, there have been more than 300 articles published describing Doppler studies in the field of obstetrics. This review will analyze the data dealing with the umbilical and uteroplacental circulation. This is being done with the goal of formulating an opinion of the role of Doppler in the practice of clinical obstetrics. We have concluded from prospective studies that there is no clear definition of abnormal umbilical flow velocity before 30 weeks, except for absent end-diastolic velocity after the 20th week. Most of the prospective studies on the uteroplacental circulation have suffered from a lack of knowledge of the umbilical circulation, or only one uterine artery was studied. Most investigations until now have focused on demonstrating the pathophysiological correlations with Doppler studies. With the exception of a few dissenting voices, most have demonstrated strong correlations at probability levels of less than 0.01. A few studies have emerged that have attempted to evaluate Doppler as a screening or surveillance tool. The results have not been encouraging. In populations with a low perinatal mortality, it will be difficult to prove that Doppler will reduce perinatal mortality. Studies of Doppler efficacy will have to be designed to show improved usage and efficacy of fetal surveillance. Since Doppler uniquely identifies the fetus at risk for hypoxia before term, it could replace our current risking system for the detection of fetal disease.(ABSTRACT TRUNCATED AT 250 WORDS)

The diagnostic efficacy of the umbilical arterial systolic/diastolic ratio as a screening tool: a prospective blinded study

This prospective blinded study investigated the diagnostic efficacy of the umbilical arterial systolic/diastolic ratio performed at 34 to 36 weeks' gestation for identifying pregnancies at a high risk for adverse perinatal outcomes. A series of 350 consecutive singleton pregnancies were included in the study. A continuous-wave Doppler instrument with a 4 MHz transducer was used. The criteria for an abnormal perinatal outcome included intrauterine growth retardation, an Apgar score of less than 7 at 5 minutes, umbilical arterial pH at birth less than 7.20, presence of thick meconium, fetal distress in labor, and neonatal complications necessitating admission to the neonatal intensive care nursery. The analytic techniques included determination of the receiver operating characteristic curve, sensitivity, specificity, positive and negative predictive values, and the kappa index. The results demonstrated that although the cutoff value of 2.9 showed the maximum inherent discriminatory power, its diagnostic efficacy (sensitivity, 0.83; specificity, 0.87 positive predictive value, 0.74; negative predictive value, 0.92; and kappa index, 0.68) was not substantially different from that of the more common cutoff value of 3.0 (sensitivity, 0.79; specificity, 0.93; positive predictive value, 0.83; negative predictive value, 0.91; and kappa index, 0.73). Both values were rated good to excellent by the kappa index. The study also demonstrated that the systolic/diastolic ratio was a better predictor of general abnormal outcome than of the suboptimal fetal growth.

The relationship between the umbilical artery systolic/diastolic ratio and umbilical blood gas measurements in specimens obtained by cordocentesis

The purpose of this investigation was to prospectively determine the relationship between the umbilical artery systolic/diastolic ratio and the umbilical blood gases in samples obtained from 165 fetuses during diagnostic cordocenteses. In each instance the sample was the umbilical vein. The systolic/diastolic ratio was measured in a midsection of the umbilical cord. Analyses used stepwise, multiple linear regression. The mean +/- SEM gestation was 29 +/- 0.4 weeks; 72% of fetuses were greater than or equal to 25 weeks and were considered potentially viable. There was no relationship between the umbilical artery systolic/diastolic ratio and pH, PCO2, or PO2 in fetuses either less than 25 weeks' gestation or greater than or equal to 25 weeks' gestation but with systolic/diastolic ratios greater than or equal to the 95th percentile for control fetuses at 25 weeks' gestation with normal blood gas values (3.5). In fetuses greater than or equal to 25 weeks' gestation with systolic/diastolic ratios that exceeded 3.5 (n = 37), there was a strong relationship between the systolic/diastolic ratio and the umbilical venous PO2 (r = -0.68, p less than 0.0001), which was independent of gestational age. Each fetus with repetitively absent-reversed umbilical artery diastolic blood flow and a heart rate greater than 90 beats/min (n = 6) had blood gas measurements consistent with hypoxia and acidosis. This investigation suggests that factors that lead to an increase in the umbilical artery systolic/diastolic ratio are associated with a progressive impairment of placental gas exchange and that by the time diastolic flow is lost, hypoxemia is present.

Contraction stress fetal heart rate monitoring at preterm gestational ages

The evaluation of fetal well-being by fetal heart rate monitoring at preterm gestational ages remains a difficult and important area for investigation. While the nonstress test has achieved widespread usage, a role for the contraction stress test remains uncertain. This study describes the outcome of 113 contraction stress tests which were performed for persistent fetal heart rate nonreactivity in 78 pregnancies of less than 37 completed weeks' gestation. There were no fetal deaths and no obstetric complications which could be attributed to these tests. The finding of a negative contraction stress test provided reassurance which facilitated significant prolongation of pregnancy. Contraction stress test appear to be a safe and effective method of investigating further the clinical dilemma of persistent fetal heart rate nonreactivity in high risk pregnancies at preterm gestational ages.

Doppler findings in the fetal and uteroplacental circulation: a promising guide to clinical decisions

The combination of real time and Doppler ultrasonic methods has opened up new possibilities for the study of fetal and uterine haemodynamics in humans particularly for the umbilical, uterine and fetal cerebral arteries. A pathological finding in blood velocity waveforms seems to be an early and consistent alteration which precedes other markers of chronic fetal distress. The challenges are to differentiate between fetal and uteroplacental aetiologies of chronic fetal asphyxia and to search for effective treatment of early fetal distress. Recent data on the practical value of haemodynamic studies in different perinatal complications is presented in this review.

A comparison between umbilical artery velocimetry and standard antepartum surveillance in hospitalized high-risk patients

One hundred forty-six women admitted to the high-risk obstetric unit between November 1987 and December 1988 participated in a study designed to compare Doppler umbilical artery flow studies with standard antepartum testing in the prediction of adverse fetal outcome. A Doppler ultrasound examination was considered abnormal when the average systolic/diastolic ratio was greater than or equal to 4. The antepartum testing consisted of a combined use of nonstress testing and contraction stress testing. If both the Doppler systolic/diastolic ratio and the antepartum testing were abnormal, there was a significantly increased incidence of intrauterine growth retardation (47%), fetal distress necessitating cesarean section (67%), and admission to neonatal intensive care (86%). Doppler umbilical artery flow studies are an important adjunct to antepartum fetal surveillance in high-risk patients but should not determine clinical management when standard antepartum surveillance remains normal.

Blood flow: insights from ultrasound

Ultrasonic pulse-echo systems can provide range-finding, time-position and real-time two-dimensional images of soft-tissue structures within the body. The Doppler effect can be used to study motion and blood flow. Continuous wave Doppler instruments provide information about velocity and direction of flow; depth discrimination can be obtained by pulsing the ultrasound. Two-dimensional Doppler flow imaging can be achieved by manual scanning of a probe over the skin surface. The combination of real-time pulse-echo imaging with pulsed Doppler blood flow detection in the duplex scanner makes it possible to localize the anatomical position of the Doppler sample volume. Real-time Doppler colour flow imaging combines traditional ultrasonic scanning with a two-dimensional flow map. Using appropriate ultrasonic instruments, blood flow volume rates, blood flow velocity profiles, pressure gradients, orifice areas, flow disturbances, jets, characteristics of blood vessels and the circulatory system, and tissue perfusion can all be investigated. These investigations have clinical applications in the study of cardiac, cerebral and peripheral blood flow, blood flow in the female pelvis, the fetus, the abdomen, the neonate, and in malignant tumours. Contemporary ultrasonic diagnosis employs exposure levels that are apparently free from biological risk, but other factors need to be taken into account in considering the prudent use of ultrasonic methods. Promising research is being carried out into the mechanism of ultrasonic scattering by blood, Doppler speckle, time-domain processing for blood flow imaging, methods for increasing the scanning speed, Doppler flow microscopy and contrast agents. The new technology that will result from this research should lead to further substantial progress in ultrasonic blood flow studies.

Direct determination of the ovine fetal umbilical artery blood flow waveform

Ultrasonographic umbilical artery blood flow velocity waveform analysis has been proposed as a means of noninvasive assessment of fetal well-being. We computed waveform indices from directly measured umbilical artery blood flow in chronically instrumented ovine fetuses from 109 to 138 days of gestation (term, 145 days). The three waveform indices (systolic/diastolic ratio, pulsatility index, and resistance index) correlated significantly with each other (r = 0.90 to 0.98). These indices progressively decreased with gestation and were significantly correlated with calculated umbilical vascular resistance (r = 0.68 to 0.70, p less than 0.01) and with umbilical blood flow (r = -0.71, p less than 0.01). During the final week of pregnancy, systolic/diastolic ratio could be predicted by the combination of placental size (total cotyledonary mass), fetal size (ponderal index), and either umbilical blood flow or umbilical vascular resistance (multiple linear regression, r2 = 0.94). Fetal heart rate declined from day 109 of gestation to 138 days. Fetal heart rate was significantly correlated with waveform indices only when values exceeded 170 beats/min (r = -0.37 to -0.51). Ovine fetal umbilical artery waveform indices changed at approximately the same rate as those reported for human fetuses in late gestation on the basis of external Doppler ultrasonographic velocity measurements. These results suggest that the sheep is a suitable model for investigations of umbilical artery waveform analysis.

Predictive values of umbilical artery waveforms and repeat cardiotocography in pregnancies complicated by nonreactive cardiotocography

Fifty patients with a nonreactive nonstress cardiotocograph were studied. All had measurement of the A/B ratio of the umbilical artery Doppler waveform and 39 also had a repeat nonstress test. The positive and negative predictive values of the repeat nonstress test were 61% and 94%, respectively, and those of the A/B ratio were 67% and 83%. A repeat nonreactive nonstressed cardiotocograph appeared to be a test of high sensitivity (92%) and the A/B ratio a test of high specificity (83%). It is suggested that the combination of the two tests may prove a powerful predictor of adverse perinatal outcome.

Umbilical flow waveforms versus fetal biophysical profile in hypertensive pregnancies

The pulsatility index (PI) of the umbilical arteries was measured in 40 hypertensive pregnancies. Doppler-velocimetric data were kept unknown to the clinical staff. An abnormal PI was found in 79% of cases in which an abnormal fetal growth in utero had been diagnosed by ultrasonographic measurements. Serial PI findings showed worsening figures in most of the cases with an abnormal fetal growth, irrespective of the last absolute value. Amniotic fluid estimation and PI data were significantly correlated. PI values were markedly abnormal in fetuses with non-reactive heart-rate tracings. A high sensitivity and an optimal specificity were found for umbilical PI versus the diagnosis of fetal growth retardation made by the coexistence of different biophysical criteria. However, false normal results may occur. 62% of the newborns weighed below the 5th percentile. The sensitivity of abnormal PI values to detect these light fetuses resulted to be only 67%. However the prevalence of neonatal morbidity in fetuses with abnormal PI values was 74%, while morbidity occurred only in 14% of cases with normal PI values. In hypertensive pregnancies, this simple velocimetric parameter proved to correlate with abnormal biophysical monitoring and complicated neonatal outcomes.

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.

Intrapartum Doppler velocimetry, amniotic fluid volume, and fetal heart rate as predictors of subsequent fetal distress. I. An initial report

This study examines the usefulness of umbilical artery Doppler velocimetry, amniotic fluid volume assessment, and fetal heart rate data in the early intrapartum period as predictors of subsequent fetal distress. A total of 109 patients seen in the latent phase of labor in the labor and delivery area were studied. Both an abnormal initial fetal heart rate and an amniotic fluid index less than or equal to 5.0 cm were associated with a significant increase in the incidence of intrapartum fetal distress. Conversely, a systolic/diastolic ratio greater than 3.0 by Doppler ultrasonography was not associated with increased fetal morbidity. Overall, the sensitivities, specificities, and positive predictive values of the fetal heart rate tracing and the amniotic fluid volume assessment were comparable. Doppler systolic/diastolic ratios showed very poor sensitivity and positive predictive value. We conclude that the fetal heart rate tracing or the assessment of amniotic fluid volume in the early intrapartum period are reasonable predictors of subsequent fetal condition. The lack of patients with the absence of or reverse umbilical velocity preclude conclusions with regard to Doppler systolic/diastolic ratios for this purpose.

Antiphospholipid antibodies and reproduction

Antiphospholipid antibodies (APAs) may be identified in the laboratory by using either coagulation studies or solid-phase immunologic assays (ELISA; RIA). These methodologies do not necessarily evaluate the same antibody; consequently, it is appropriate to screen a patient's plasma by utilizing both assays. APAs have been associated with a variety of obstetrical complications including recurrent spontaneous abortion, intrauterine fetal death, early onset preeclampsia, deep vein thrombosis, and postpartum serositis syndrome. The Kaolin Clotting Time appears to be the most sensitive coagulation test for identifying the lupus anticoagulant. However, preliminary studies would suggest the presence of anticardiolipin antibodies as detected by solid-phase assays are more sensitive and predictive of the clinical course. Although there are no prospective trials to analyze treatment of patients with APA, preliminary data suggest the use of prednisone in combination with aspirin significantly improves the probability of delivery of a viable infant. In addition, heparin, intravenous gammaglobulin, and exchange plasmaphoresis have all been tried with varying degrees of success in individual patients in small series.

Doppler umbilical artery waveform indices--normal values from fourteen to forty-two weeks

Normal values for Doppler waveform indices of the umbilical artery have been reported for gestational ages of 20 to 40 weeks in small numbers of normal patients. We evaluated 590 patients studies performed at 2-week intervals from 14 to 42 weeks' gestation on patients without medical or pregnancy complications. Readings were obtained during fetal quiet times (no fetal breathing or movements). Values for A (systolic) and B (diastolic) pressures were plotted as Pourcelot (A - B/A) and A/B ratios. Mean, SD, and 95% confidence limits were derived, and the skewness, kurtosis, and regression correlations were calculated. No diastolic flow was found in any pregnancy greater than 15 weeks' gestation (n = 25) or in 50% of the gestations between 15 to 17 weeks (n = 25). When diastolic pressure equals zero, the Pourcelot ratio value equals one and the A/B ratio approaches infinity and loses meaning. Recent work by Thompson et al. suggests that the Pourcelot ratio fits a normal distribution from 20 to 40 weeks' gestation and that the A/B ratio (which does not fit a normal curve) may be transformed to a normal distribution by conversion of the A/B ratio to 1/1 - Pourcelot ratio. Our data supports the normality of both indices from 18 to 42 weeks' gestation, but these assumptions are not applicable as the Pourcelot ratio approaches one or as the A/B ratio approaches infinity. Knowledge of normal umbilical flow ratios at gestational ages from 18 weeks may allow early detection and directed management of high-risk pregnancies.

[Measuring fetal vascular resistance with the Duplex scanner--a new fetal stress test]

In 77 women (phi 41 week, less than 7 days before delivery) we compared the resistance index (RI) in the umbilical artery (UA), descending aorta (DA) and intracranial artery (ICA) with an oxytocin challenge test (OCT) and a non stress test (NST). Proof criterias were asphyxia resulting in operative deliveries and metabolic acidosis. The sensitivity in predicting metabolic acidosis was low in all tests, but a high and comparable specificity could be achieved in both the RI and OCT. In predicting fetal asphyxia the RI in the ICA had a high sensitivity, the RI in the UA and DA had the highest specificity of all tests. Centralisation and increased brain perfusion seem to detect fetal asphyxia as a result of placental insufficiency.