Doppler flow velocimetry of the umbilical artery, uteroplacental arteries and fetal middle cerebral artery in prolonged pregnancy

A total of 153 pregnant women, of at least 287 days' menstrual age, were studied in a prospectively designed cross-sectional trial. In addition to the non-stress test, contraction stress test, sonographic estimate of amniotic fluid and grade of placental maturation, Doppler measurements of the resistance index (RI) were taken in the umbilical artery, the uteroplacental arteries in the region of placental implantation and the fetal middle cerebral artery. Data were analyzed with regard to asphyxia and otherwise complicated fetal outcome. Furthermore, a possible relationship between grade of placental maturation, Doppler flow velocity waveforms and fetal outcome was investigated. Doppler resistance indices in the umbilical artery, uteroplacental arteries in the region of placental implantation and fetal middle cerebral artery did not change significantly with increasing gestation from 41 to 43 weeks. The grade of placental maturation on ultrasound examination was not related to fetal outcome or Doppler indices in the first two vessels. In all vessels examined in this study, the majority of Doppler measurements in pregnancies with subsequent asphyxia or otherwise complicated fetal outcome were within the 95% prediction interval for patients with normal fetal outcome. None of the patients showed absent diastolic flow in the umbilical artery. With the use of a cut-off value of RI = 0.62 in the umbilical artery, asphyxia could be predicted with 37% sensitivity and 75% specificity. Oligohydramnios and antpartum cardiotocography predicted asphyxia with 16% and 8% sensitivity and 95% and 96% specificity, respectively. Sensitivity for prediction of otherwise complicated fetal outcome by umbilical artery Doppler was only 7%.(ABSTRACT TRUNCATED AT 250 WORDS)

Longitudinal measurement of amniotic fluid index in postterm pregnancies and its association with fetal outcome

OBJECTIVE

Our purpose was to study the association between dynamic changes in serial amniotic fluid index measurements and adverse fetal outcome in postterm pregnancies.

STUDY DESIGN

Serial amniotic fluid index values were obtained semiweekly in 139 reliably dated, uncomplicated, singleton pregnancies at > 41 weeks' gestation. Adverse fetal outcome was defined by the presence of moderate or thick meconium, fetal heart rate decelerations, cesarean delivery for fetal distress, neonatal intensive care unit admission, and perinatal mortality.

RESULTS

Prominent changes in the amniotic fluid index (i.e., > 50% increase or decrease) had no association with adverse fetal outcome irrespective of rate of change, provided the final value remained > 5.0 cm. A significant association with fetal heart rate decelerations and the presence of meconium was detected only in patients whose final amniotic fluid index was < or = 5.0 cm (p = 0.007 and p = 0.003, respectively).

CONCLUSION

Irrespective of the rate of change in amniotic fluid index, postterm pregnancies are significantly associated with potential complications such as fetal heart rate decelerations and meconium staining when the final amniotic fluid index is < or = 5.0 cm.

Prolonged gestation, decreased triiodothyronine concentration, and thyroid gland histomorphologic features in newborn foals of mares grazing Acremonion coenophialum-infected fescue

Newborn foals of mares grazing on Acremonium coenophialum-infected fescue pasture throughout gestation or from gestation day 300 to parturition had increased gestation duration and decreased serum triiodothyronine concentration. Pregnant mares were allotted to 4 treatments: grazing continuously on endophyte-free (E-) fescue, grazing continuously on endophyte-infected (E+) fescue, grazing on E+ fescue from gestation day 300 to parturition, and grazing on E+ fescue from conception to gestation day 300. Morphometric studies indicated that foals born to mares exposed to endophyte late in gestation had large, distended thyroid follicles lined by flat cuboidal epithelial cells. Mean triiodothyronine concentration in foals exposed to endophyte (395.2 ng/dl) was decreased (P < 0.01), compared with mean values in control foals (778.0 ng/dl). Thyroxine and reverse triiodothyronine concentrations were not significantly different among groups. Foal organ weight as a percentage of foal body weight was not significantly different among experimental groups.

[Prolonged pregnancy--prostaglandins as the cause of labor onset]

The causes of prolonged pregnancy are still largely unknown and their investigation requires a detailed observation of potential birth-initiating stimuli on the endocrine and biomolecular level. A large number of clinical and biochemical studies point to the central importance of prostaglandins for the beginning of human birth. The main places of origin of the intensified prostaglandin formation and release are the amnion and the decidua which has "macrophage-like" properties and functions. The superordinate regulation and trigger mechanisms for intensified uterine prostaglandin production has not been sufficiently investigated either. Possible factors currently being debated include local changes in estrogen and progesterone biosynthesis in fetal membranes and decidua, subclinical inflammatory reactions with the activation of macrophages and the consecutive release of cytokines, and a loss of maternal immune tolerance with a time-determined rejection reaction. In addition, the substances inhibiting and stimulating prostaglandin synthesis have been detected in the amniotic fluid, fetal membranes and decidua. The fetus itself also plays an important part in the initiation of labor. Prolongation may be due to anatomic functional disturbances of the one hand which prevent the activation of the fetal hypothalamic-hypophyseal-adrenal axis and the release of the birth-initiating stimuli originating in the fetus; on the other hand, an elevated immune tolerance with a delayed rejection reaction or the lack of "bacterial stimulus" may inhibit the activation of the macrophages and hence the formation of cytokines. The consequences would be the development and release of a quantity of prostaglandins from the fetal membranes and decidua insufficient to overcome the pregnancy-maintaining safety systems.(ABSTRACT TRUNCATED AT 250 WORDS)

Management of post-term pregnancy: to induce or not?

Perinatal mortality is increased in pregnancies over 42 weeks, but can be reduced by the induction of labour. However, clinicians must consult with the patient as to whether she would rather experience spontaneous onset of labour or accept this increased risk. This article weighs up the important considerations in this difficult area.

[Doppler findings--placental morphology: correlation and divergence of findings]

Based on 132 histomorphological placental investigations and their related Doppler test results, the question was asked, whether a strong correlation exists between Doppler test results and histomorphological placenta results, and whether these are uniform with respect to histomorphological changes. The results showed that all histomorphologically inconspicuous placenta findings were also inconspicuous doppler-sonographically. The viewing resulted in no histomorphologically unifying aspect of change. However, the investigation was able to demonstrate, that a distinction must be made between acutely developing changes and chronically developing changes. Along these lines, the last groups produced not only changes which compensate each other, but also changes, which are harmful to organic functioning and thus may diminish foetal supply without being detected by pulsed Doppler ultrasound.

Post-term pregnancies with normal cardiotocographs and amniotic fluid columns: the role of Doppler evaluation in predicting perinatal outcome

OBJECTIVE

To study the role of Doppler ultrasound examination in predicting an abnormal perinatal outcome, among post-term pregnancies uncomplicated by an abnormal non-stress test (NST) or reduced amount of amniotic fluid.

DESIGN

A prospective study.

SETTING

High-risk pregnancy unit, Hadassah Mt. Scopus University Hospital, Jerusalem.

SUBJECTS

Seventy-eight women with confirmed gestational age of > 287 days, who had normal initial evaluation and unfavourable cervical examination.

INTERVENTIONS

Doppler flow velocity waveforms were recorded from the umbilical and middle cerebral arteries, and from the descending thoracic aorta.

MAIN OUTCOME MEASURES

Correlation between Doppler measurements and data regarding delivery.

RESULTS

Women who developed signs of fetal distress during labour, or who required intervention because of fetal distress, had elevated umbilical artery systolic/diastolic ratio, decreased middle cerebral artery pulsatility index, and decreased time average aortic blood flow velocity. Umbilical artery Doppler measurements could significantly predict the need for intervention due to fetal distress.

CONCLUSIONS

Doppler examination of uncomplicated post-term pregnancies may identify patients with normal results as having a low risk of developing fetal distress during labour. Patients with abnormal Doppler results are prone to need intervention following fetal distress in labour.

[Development of Doppler parameters in fetal and maternal blood vessels 10 days before to 10 days after the calculated due date]

Doppler sonography can help to assess a foetal risk situation prospectively. This procedure is therefore well suited for the screening of risk pregnancies in the 3rd trimenon. The role of Doppler ultrasound at delivery is still controversial, since, on the one hand, no data on the behaviour of Doppler parameters directly at the onset of delivery are available, and on the other hand the obstetric consequences from pathological findings are not clear. For this reason, we observed 45 normal pregnancies from the 10th day prior to the date of confinement till the 10th day post partum. In 20 patients we registered Doppler parameters from 4 days before until the onset of true labour. In all these cases, a reduction of the end-diastolic blood flow in the foetal aorta was found, which became evident by the increase of the resistance index to pathological values. Concomitant decrease of the resistance index in the foetal carotid artery was typical for a circulatory system. Since foetal outcome was normal in all newborn, this change in Doppler parameters directly at the beginning of labour must be considered as physiological. The findings suggest a physiological placental insufficiency. Since however, parameters in the uterine vessels did not show any changes, the insufficiency has its probable origin in the placenta. From these findings, one might speculate, that the supply deficiency is the labour inducing factor. No clinical consequence can thus result from pathological Doppler data found in patients directly prior and after delivery. Cardiotocographic screening is necessary.(ABSTRACT TRUNCATED AT 250 WORDS)

Fetal renal pulsed Doppler waveform in prolonged pregnancies

OBJECTIVE

Our purpose was to determine Doppler waveforms of the fetal human renal artery in prolonged pregnancy in the presence or absence of oligohydramnios.

STUDY DESIGN

Fifty patients at or after 40 weeks were studied. Ultrasonography was performed to determine the amniotic fluid index by the four-quadrants technique. Two groups of patients were obtained on the basis of the amniotic fluid index. Group 1 had an amniotic fluid index > 5 (normal) (n = 33); group 2 had amniotic fluid index < or = 5 (oligohydramnios) (n = 17). Umbilical artery and fetal renal pulsed Doppler waveforms were determined and analyzed. The fetal renal artery systolic-to-diastolic ratio of the two groups was compared.

RESULTS

Fetuses with a low amniotic fluid index had a significantly higher ratio. A significant negative correlation coefficient between amniotic fluid index and fetal renal systolic/diastolic ratio was found (r = -0.435 and p < 0.01).

CONCLUSIONS

In prolonged pregnancies there is a significant relationship between the amniotic fluid index and the fetal renal systolic/diastolic ratio. In pregnancies associated with oligohydramnios the systolic/diastolic ratio is significantly higher than in those with normal amniotic fluid volume. These data suggest that intrarenal flow in prolonged pregnancies complicated with oligohydramnios is significantly different.

[Doppler ultrasound diagnosis in post-term pregnancy]

The capability of Doppler flow velocimetry to predict intrauterine growth retardation is well known. The increased morbidity and mortality rate of postterm newborns is also well known. The aim of our study was to examine if Doppler flow velocimetry is able to indicate foetal jeopardy in the postterm period. Flow velocimetry of the foetal descending aorta, the umbilical artery, the uterine arteries and in 59 cases also the foetal middle cerebral artery was obtained from 167 pregnancies after 40 completed weeks of gestation. We found significant changes of normal values in prolonged pregnancy compared to third trimester normal values, examining the mean velocity of the foetal descending aorta and the S/D-ratio of the umbilical artery. No clinically significant changes were found examining the S/D-ratio of the uterine arteries and the pulsatility index of the foetal middle cerebral artery. Daily examinations of the foetal descending aorta were carried out in 23 and of the umbilical artery in 19 cases during the last four days before delivery, and in 11 cases of the foetal middle cerebral artery during the last three days before delivery. We did not find significant changes in the medians of the mean velocity of the foetal aorta, of the S/D-ratio of the umbilical artery and of the pulsatility index of the foetal middle cerebral artery. Measurement of sensitivity and positive predictive value of the four arteries examined showed, that Doppler ultrasound could not predict small for date infants or Caesarean section because of foetal distress.(ABSTRACT TRUNCATED AT 250 WORDS)

Amniotic fluid volume estimation in the postdate pregnancy: a comparison of techniques

OBJECTIVE

To determine the amniotic fluid (AF) volume estimation technique with the greatest diagnostic value with respect to perinatal outcome in the postdate pregnancy.

METHODS

One hundred ninety-eight women who were at least 40 weeks' gestation based on ultrasound confirmation or establishment of dates were evaluated twice weekly with nonstress tests (NSTs) and AF volume estimation. Various indices of AF volume were measured and correlated with perinatal outcome. Receiver operating characteristic curves were used to determine optimal cutoff values.

RESULTS

There was a significantly larger maximal vertical pocket in those pregnancies with a normal perinatal outcome than in those with abnormal outcome (4.2 +/- 1.4 versus 3.2 +/- 2.0 cm; P = .02). A statistically significant difference was also seen with the AF index (10.0 +/- 4.5 versus 7.5 +/- 5.0 cm; P = .01). Analysis revealed that the optimal cutoff for identifying clinically significant oligohydramnios was a largest vertical pocket less than 2.7 cm, with an adjusted odds ratio for abnormal perinatal outcome of 7.11 (95% confidence interval [CI] 2.79-18.16). Its sensitivity of 50.0% and specificity of 87.9% were superior to the diagnostic value of the AF index of 5 cm, which had a sensitivity of 29.2% and specificity of 89.1%.

CONCLUSION

A largest vertical pocket threshold of 2.7 cm had the greatest diagnostic value for identifying the postdate pregnancy at risk for abnormal perinatal outcome, surpassing the AF index and the 2-cm largest vertical pocket rule.

The value of Doppler ultrasonography in prolonged pregnancies

One hundred forty-two gravid women at term were followed prospectively by a non-stress test, estimation of amniotic fluid volume and Doppler velocimetry of the umbilical and uterine arteries. Adverse perinatal outcome was detected in 12 women (8.5%). Abnormal antepartum tests were detected in 26 women (17%). Seven women had an abnormally elevated resistance index (RI) in the umbilical artery; but only two had an abnormal outcome. Seven women had an abnormally elevated RI in the uterine artery, but only two had abnormal outcome. Three out of 11 women with oligohydramnion had abnormal perinatal outcome. Only one out of seven women with an abnormal non-stress test had abnormal perinatal outcome. In six women, more than one antepartum test was abnormal. The various surveillance methods demonstrated a low sensitivity (the highest was obtained by estimating amniotic fluid volume: 25%) and a low positive predictive value (the highest obtained by measuring the resistance index in either the umbilical or the uterine arteries: 28.6%). By considering any abnormal test as a positive test result for a given patient, a substantial improvement in sensitivity (66.7%) and positive predictive value (33.3%) are obtained. Doppler velocimetry adds very little in itself to the follow-up of patients with post-term gestations. However, when combined with additional antepartum tests, it may increase our ability to predict the compromised fetus in this condition.

Clinical significance of fetal heart rate patterns during labor. IX: Prolonged pregnancy

The intrapartum FHR and UC were recorded in a population of 707 consecutive cases of prolonged gestation looking for a characteristic pattern. There is no typical pattern for prolonged pregnancy. However, there are differences from preterm and term populations. There is a very high incidence of variable (55%) and late (17%) decelerations. These were seen more frequently among cases receiving oxytocin. Nearly 50% of C-sections had lates. Baseline alterations (tachycardia 26%, fixed 8%, and saltatory 17%) were often associated. Apgar scores < or = 6 at 1 minute were correlated with variable and late decelerations. However, acidemia (UA pH < or = 7.20) could not be predicted from FHR patterns because there was no correlation between low pH and clinical depression. Alarmingly a few fetuses in agonal state presented normal appearing tracings, or deteriorated rapidly without the usual indicative changes by FHR. All intrapartum or NND had this misleading pattern. In view of this unpredictable aberrant pattern as the only certain means to prevent these deaths, it is suggested that no pregnancy should be allowed to reach 294 days post LMP.

[Determination of birth date by early ultrasonography]

Ultrasound examination has become an indispensable tool in antenatal care. In cases with intrauterine growth retardation, post-term pregnancy and when deciding elective delivery, knowledge about gestational age is essential. However, criticism has been raised against its routine use to determine gestational age. Ultrasound is subject to a certain degree of variation, as is determination of gestational age on the basis of the last menstrual period. Variation is less by ultrasound, which therefore reduces the number of "post-term" pregnancies. The consequences of post-term pregnancy are discussed.

Prospective evaluation of the contraction stress and nonstress tests in the management of post-term pregnancy

Eight hundred and nineteen patients were evaluated at greater than or equal to 280 days' gestation. All patients underwent nonstress test (NST) and breast stimulation to induce contraction stress test (CST), except where contraindicated. If CST was nonqualifying (less than three contractions per ten minutes), Pitocin (oxytocin) was used to complete the CST if there was a nonreactive NST. Delivery was instituted for any abnormal CST, even with a reactive NST, based on the last test within seven days of delivery. There were 747 reactive NST and 72 nonreactive NST. Breast stimulation for CST was done in 655 instances--315 (48 per cent) had nonqualifying CST and 340 (52 per cent) had qualifying CST. There was an increased incidence of induction in the nonqualifying CST group and abnormal CST group. There were no statistically significant differences in perinatal outcomes in the group with reactive NST, irrespective of the CST result. There were no antepartum fetal deaths.

The effect of hypothalamic lesions on the length of gestation in fetal sheep

Twenty-nine sheep fetuses were subject to stereotaxic surgery at 106 to 110 days of gestation. Electrolytic lesions were placed bilaterally in the anterior hypothalamus. Sham-operated controls (n = 4) were delivered at 146.3 +/- 4.3 days. Of the fetuses with lesions, two were excluded because histologic confirmation of the lesion was not possible. Those fetuses with bilateral lesions of the suprachiasmatic nuclei (n = 4) were delivered at 148 +/- 10 days. In 10 animals with bilateral lesions of the paraventricular nuclei, delivery was significantly (p less than 0.0001) prolonged to at least 165.6 +/- 5.1 days. In nine animals with lesions not involving the endocrine hypothalamus, delivery was at 148.1 +/- 4.3 days. All animals that were delivered after 157 days (n = 9) had lesions including the paraventricular nuclei bilaterally (p less than 0.01). The adrenal glands of fetuses with prolonged gestation were normal in weight and light microscopic appearance. These observations demonstrate that fetal neural pathways involving the paraventricular nuclei are essential for parturition in the sheep. However, fetal adrenal growth can continue without such influences.

Placental lactogen secretion during prolonged-pregnancy in the rat: the ovary plays a pivotal role in the control of placental function

The serum of rats at mid-pregnancy contains at least 2 distinct placental lactogen (PL)-like substances tentatively termed placental lactogen-alpha (PL-alpha) and placental lactogen-beta (PL-beta) (Endocrinol Japon 38: 533-540, 1991). We have investigated the secretory patterns of three placental lactogens (PL-alpha, PL-beta and placental lactogen-II) during normal pregnancy and in two prolonged-pregnancy models. Pregnancy was prolonged by the introduction of new corpora lutea by inducing ovulation on day 15 of pregnancy by successive treatments with PMSG (30 IU/rat, sc on day 12) and hCG (10 IU/rat, iv on day 14), and in the second model by progesterone implants on day 15 of pregnancy. During normal pregnancy, each of the 3 PLs exhibited only one secretory peak in the serum; PL-alpha and PL-beta on day 12 and placental lactogen II (PL-II) on day 20. Interestingly, in the rats with new sets of corpora lutea, serum PL-alpha and PL-beta levels began to increase again on day 18 and showed peaks on day 20 for PL-alpha and on day 22 for PL-beta. In this model, the initiation of PL-II secretion was not affected, but high levels were maintained until day 26, when parturition occurred. In rats receiving either PMSG or hCG, the secretory patterns of the PLs were similar to as those during normal pregnancy.(ABSTRACT TRUNCATED AT 250 WORDS)

Doppler evaluation of umbilical and uterine-arcuate arteries in the postdates pregnancy

To assess the correlation between Doppler velocimetry and perinatal outcome in the postdates pregnancy, 75 women who were at least 41 weeks' gestation were evaluated twice weekly until delivery. Evaluation included Doppler velocimetry of the umbilical and uterine-arcuate arteries, as well as nonstress testing and amniotic fluid volume estimation. The mean umbilical artery systolic-diastolic ratio (S/D) was significantly higher in the pregnancies with subsequent abnormal perinatal outcomes than in those with normal outcomes (2.42 versus 2.19; P = .03). Using a receiver operating characteristic curve, an abnormal umbilical artery S/D was defined as 2.40 or greater. Using this value, sensitivity was 57.1% and specificity was 77.8%. Our study suggests that an umbilical artery S/D of 2.40, rather than the more traditionally accepted cutoff of 3.0, may be a useful threshold to identify those postdates pregnancies at high risk for abnormal perinatal outcome.

[Ultrasound Doppler sonography in obstetrics. A comparison between simple Doppler methods (continuous or pulsed Doppler) and the duplex system (combination of B-image and pulse Doppler)]

120 pregnant women between the 26th and 42nd week of gestation have been examined using simple Doppler-units with pulsed- or continuous-wave technique and duplex Doppler-units (combined B-mode and pulsed-wave Doppler). The umbilical and uterine arteries were measured with both units in a semi-recumbent position at the same time by the same examiner. Only ideal flow profiles were taken to calculate the S/D-ratio. Our results were correlated to the fetal outcome, to all cases of pre-eclampsia and to all cases of intra-uterine growth retardation. Except in one of these cases we got the majority of pathological results using simple Doppler-units. Only in pre-eclampsia the duplex Doppler-units had the majority of pathological results. Even in normal fetal outcome the majority of simple Doppler-unit results are pathological. This finding is due to the impossibility to localize the vessel exactly using simple Doppler-units. Sensitivity is higher in simple Doppler-techniques (74.3% to 52.9%), specificity is higher in duplex Doppler-technique (77.9% to 52.6%).

Doppler flow velocity waveform analysis in postdate pregnancies

This study examines the efficiency of Doppler flow velocity waveform analysis in the evaluation of the postdate pregnancy. Seventy women whose pregnancies were at or beyond 41 weeks' gestation were assessed by calculating the systolic/diastolic ratios from umbilical and uteroplacental arteries. Waveform ratios from pregnancies associated with fetal compromise and abnormal neonatal outcome were similar to those from pregnancies in which the outcome was normal. These findings indicate that the pathophysiology of placental insufficiency in postdate pregnancies differs from that observed in cases of fetal growth retardation at earlier gestational ages. Doppler flow velocity waveform analysis is unlikely to be of benefit in the routine assessment of the postdate pregnancy.