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Biomedical subjects

J P Newnham

Publications and source records attributed to J P Newnham.

At least 19 recordsLinked to original sources
PubMed1994

Catecholamine response to ultrasonographically guided percutaneous blood sampling in fetal sheep.

OBJECTIVE: The purpose of this study was to investigate the fetal catecholamine and arterial blood gas responses to ultrasonographically guided percutaneous needle aspiration of blood from a fetal cardiac ventricle. STUDY DESIGN: A crossover trial design was used. Nine pregnant sheep of 120 to 130 days' gestation were stratified to either percutaneous fetal blood sampling or a sham experiment performed on the first day, and the alternative study on the following day. Arterial blood samples were withdrawn from chronically implanted catheters. RESULTS: Percutaneous fetal blood sampling caused small but statistically significant increases in mean plasma epinephrine and norepinephrine levels 5 seconds after the procedure. Levels thereafter were similar to baseline values. Arterial pH and PCO2 values were unaltered except in one fetus, where blood sampling was followed by bradycardia with acidosis and elevated catecholamine levels. CONCLUSIONS: Ultrasonographically guided percutaneous fetal blood sampling from a cardiac ventricle in sheep produces a rise in catecholamine levels that return to baseline values within 5 minutes. This technique provides an alternative to chronic catheterization for some experiments in which blood sampling or drug injection is required. The results also indicate that needle insertion produces only a modest and transient stress response in the fetus.

Animals↗
PubMed1994

Time course of changes in lung mechanics following fetal steroid treatment.

We studied the effect of a single-dose, corticosteroid treatment on preterm lambs (gestational age: 128 d). A low, medium, or high betamethasone dose (0.1, 0.5, and 2.0 mg/kg) or saline control was administered directly to the fetus by ultrasound-guided intramuscular injection 48 h before delivery. A second group received either the high dose of betamethasome or saline 24 h before delivery. The lambs were delivered at 128 d gestation, anesthetized with ketamine, and ventilated for 50 min. Respiratory system elastance and resistance were measured at 10-min intervals using multiple linear regression analysis of pressure, flow, and volume. Similarly, estimates of lung mechanics were calculated from transpulmonary pressure. The viscoelastic time constant (tau) was calculated by fitting an exponential to the pressure changes occurring after occluding the airway during expiration. Excised lung volume at 40 cm H2O and lung weight were used to calculate specific elastance and resistance correcting for lung size using volume or weight, respectively. Of the 13 lambs in the 48-h high-dose betamethasone group, five developed pulmonary interstitial emphysema (PIE) as did 3 of 11 animals in the high-dose group treated 24 h before delivery. These animals were analyzed separately. The lambs receiving medium- or high-dose (24 and 48 h predelivery) betamethasone had significantly lower elastance and a trend toward lower resistance when compared with the control groups. Ten minutes after delivery, the animals that developed PIE all had elastance values comparable to that of the control animals despite corticosteroid treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1993

Effects of frequent ultrasound during pregnancy: a randomised controlled trial.

Despite widespread application of ultrasound imaging and Doppler blood flow studies, the effects of their frequent and repeated use in pregnancy have not been evaluated in controlled trials. From 2834 women with single pregnancies at 16-20 weeks gestation, 1415 were selected at random to receive ultrasound imaging and continuous-wave Doppler flow studies at 18, 24, 28, 34, and 38 weeks gestation (the intensive group) and 1419 to receive single ultrasound imaging at 18 weeks (the regular group). Outcome data was obtained from 99% of women who entered the study. The only difference between the two groups was significantly higher intrauterine growth restriction in the intensive group, when expressed both as birthweight < 10th centile (relative risk 1.35; 95% confidence interval 1.09 to 1.67; p = 0.006) and birthweight < 3rd centile (relative risk 1.65; 95% confidence intervals 1.09 to 2.49; p = 0.020). While it is possible that this finding was a chance effect, it is also plausible that frequent exposure to ultrasound may have influenced fetal growth. Repeated prenatal ultrasound imaging and Doppler flow examinations should be restricted to those women to whom the information is likely to be of clinical benefit.

Adult↗
PubMed1993

A comparison of abdominal and vaginal examinations for the diagnosis of engagement of the fetal head.

The diagnosis of engagement of the fetal head is mandatory before operative vaginal delivery is to be attempted. There is widespread belief that the fetal head is engaged in the maternal pelvis when vaginal examination reveals that the bony presenting part has reached the level of the ischial spines. However, it is also claimed that in the presence of moulding the vaginal findings may be misleading and that it may be preferable to make the diagnosis by abdominal examination of the level of the fetal head in relation to the pelvic brim. In order to evaluate the relative merits of each of these 2 systems of physical examination, a retrospective study was made of 104 cases which had been evaluated for possible operative vaginal delivery by both methods. Prediction of successful vaginal delivery was greater by abdominal criteria (94%) than by vaginal criteria (80%) (p < 0.01). When evaluated by maximum likelihood logistic regression analyses, the factor of greatest importance in determining the probability of allocation of a case to each of the engagement groups was moulding (odds ratio 2.17; 95% confidence intervals 0.75-6.27). We conclude that when these 2 methods of assessment produce different diagnoses, the major factor responsible is moulding of the fetal head. Clinical evaluation prior to operative vaginal delivery must include abdominal examination and reliance on vaginal findings alone may prove misleading when moulding is present.

Adult↗
PubMed1992

Intrauterine intravascular transfusion for fetal haemolytic anaemia: the Western Australian experience.

OBJECTIVE: To report the first four years' clinical experience with fetal intravascular blood transfusion for the treatment of fetal haemolytic anaemia in Western Australia. SETTING: King Edward Memorial Hospital, Perth, which is the sole tertiary level perinatal centre in Western Australia with a referral base of approximately 25,000 pregnancies each year. METHODS: Transfusion was by injection of packed cells from Rh-negative donors into the fetal umbilical vein near the site of insertion into the placenta. Fetal haemoglobin levels were measured before and after each transfusion. In most cases, the fetus was paralysed by intramuscular tubocurarine. RESULTS: Sixty intravenous transfusions were performed in 20 pregnancies. At the time of the initial transfusion, the mean haemoglobin level was 5.8 g/dL (range, 2.5-8.5 g/dL) and six fetuses had signs of hydrops. The case survival rate was 80% and the procedure survival rate was 93%. Three of the deaths occurred in the first five cases. Caesarean section was performed during two of the procedures, one because of bleeding from the cord puncture site and one because of tamponade of the umbilical vessels. CONCLUSION: Fetal intravascular transfusion is a highly effective treatment for fetal alloimmunisation and allows pregnancies to continue to term and to be delivered vaginally. However, the procedure may be difficult and requires a team approach with ready access to fetal monitoring and emergency caesarean section. Our results suggest that increasing experience of the team is a major factor in improved outcome.

Adult↗
PubMed1992

Indomethacin for the treatment of polyhydramnios: a case of constriction of the ductus arteriosus.

Prenatal administration of indomethacin for the treatment of polyhydramnios at 27 weeks' gestation resulted in the rapid restoration of normal amniotic fluid volume. However, after 16 days therapy, fetal echocardiography revealed constriction of the fetal ductus arteriosus which did not reverse during the 17 days after the therapy was discontinued. The constriction resulted in right heart failure but no long-term effects on the infant after birth. Indomethacin is a powerful treatment for polyhydramnios but its use requires close monitoring of the fetal heart.

Adult↗
PubMed1991

Effects of extradural anaesthesia on umbilical and uteroplacental arterial flow velocity waveforms.

Flow velocity waveforms were recorded from the umbilical artery and uteroplacental arterial circulations of 15 women undergoing elective Caesarean section under extradural anaesthesia. The systolic: diastolic ratios of the flow velocity waveform were determined before and after extradural block. Extradural block did not alter fetal or maternal heart rates; however, umbilical artery systolic:diastolic ratio decreased from a mean (SD) of 2.4 (0.42) to 2.26 (0.38) (P = 0.049). There were no significant changes in the uteroplacental systolic:diastolic ratios. These results were compared with those from a control group in which no statistically significant changes in maternal and fetal systolic:diastolic ratios or heart rates were observed. The application of a pulse correction factor to standardize the data to fixed maternal and fetal heart rates had little effect on the significance of the findings. Extradural block in normal pregnant women during late gestation was associated with a small reduction in umbilical artery systolic:diastolic ratios, suggesting a decrease in downstream fetoplacental vascular resistance.

Adult↗
PubMed1991

Doppler flow velocity waveform analysis in high risk pregnancies: a randomized controlled trial.

OBJECTIVE: To test whether the introduction of Doppler waveform analysis into the ultrasound department of a tertiary level hospital reduces neonatal morbidity and improves obstetric management. DESIGN: A randomized controlled trial. SETTING: Department of Ultrasound, King Edward Memorial Hospital, Perth, Western Australia. SUBJECTS: 505 women with pregnancy abnormalities referred to an ultrasound department for fetal investigation during the third trimester. INTERVENTION: Continuous wave Doppler studies of umbilical and uteroplacental arterial circulations. Results were revealed to patients and clinicians. MAIN OUTCOME MEASURES: Principal end point was the duration of neonatal stay in hospital; other end points included the number and type of fetal heart rate monitoring studies, obstetric interventions, frequency of fetal distress, birthweight, Apgar scores and need for neonatal intensive care. RESULTS: There was no effect on the duration of neonatal stay in hospital. Small trends in obstetric management were observed with study group patients having fewer contraction stress tests, less likelihood of antepartum fetal distress, and more likelihood of fetal distress after induction of labour leading to emergency caesarean section. Depressed Apgar scores were more frequent in the study group. CONCLUSION: Introduction of Doppler waveform studies did not result in reduced neonatal morbidity but did have a small effect on obstetric management. For each institution the role of Doppler studies in late pregnancy will be influenced by the usage of other tests of fetal welfare already entrenched in clinical practice.

Female↗
PubMed1991

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.

Adolescent↗
PubMed1991

The influence of maternal undernutrition in ovine twin pregnancy on fetal growth and Doppler flow-velocity waveforms.

The effects on placental blood flow velocity of maternal undernutrition during mid pregnancy were investigated in 38 twin bearing pregnant sheep by Doppler analysis of umbilical and uteroplacental arterial waveforms. Mid pregnancy undernutrition resulted in fetal growth restriction manifest at term gestation by reduced mean birth weight. Arterial waveform systolic/diastolic ratios from the umbilical and uteroplacental arterial circulations were not influenced by maternal nutrition either during the dietary deprivation or during a subsequent period of dietary supplementation. An effect of heart rate on systolic/diastolic ratios could not be demonstrated. The results indicate that the fetus responds to mid pregnancy maternal undernutrition with restricted growth but without alterations in systolic/diastolic ratios in umbilical or uteroplacental arterial waveforms.

Animals↗
PubMed1990

An evaluation of the efficacy of Doppler flow velocity waveform analysis as a screening test in pregnancy.

In a prospective double-blind study of 535 medium-risk pregnancies, growth data obtained by ultrasonography and Doppler flow velocity waveform systolic to diastolic ratios were recorded at 18, 24, 28, and 34 weeks' gestation. A significant association was observed between uteroplacental systolic to diastolic ratios at 24 weeks' gestation and subsequent fetal hypoxia with a sensitivity of 24.0% and a specificity of 93.9%. However, 70% of abnormal results were not followed by fetal hypoxia. Umbilical artery systolic to diastolic ratios at 24, 28, and 34 weeks' gestation were found to be predictive of intrauterine growth retardation. This predictive capability was enhanced in those growth-retarded fetuses in which hypoxia developed, but was weak when umbilical artery systolic to diastolic ratios were evaluated as primary screening tests for fetal hypoxia. The results confirm a role for Doppler systolic to diastolic ratios in the evaluation of high-risk pregnancies but do not support a role for their use as primary screening tests in low-risk obstetric populations.

Adult↗
PubMed1990

Effects of maternal cigarette smoking on ultrasonic measurements of fetal growth and on Doppler flow velocity waveforms.

Serial ultrasound biometry and Doppler flow velocity waveform analysis were used to measure the effects of maternal smoking in a prospective study of 535 pregnancies. Smoking was associated with significant reductions in maternal weight gain, birthweights and placental weights. Decreased fetal biparietal diameter measurements were observed in pregnancies of smoking women; this effect was maximal at 24 weeks' gestation, was restricted to male fetuses and was not associated with altered head circumferences after birth. Umbilical artery and uteroplacental systolic/diastolic ratios were similar in pregnancies of smoking and non-smoking women, indicating that the effects of smoking on placental vascular resistance are periodic rather than continuous. The findings of this study confirm the need for studies of fetal growth to include prenatal measurements obtained by high resolution ultrasound imaging, rather than relying on findings obtainable by examination of the infant after birth.

Adult↗
PubMed1990

Effect of vibratory acoustic stimulation on the duration of fetal heart rate monitoring tests.

The ability of vibratory acoustic stimulation to shorten the duration of antepartum fetal heart rate monitoring was investigated by a randomized controlled trial. Vibratory acoustic stimulation did not shorten the overall duration of testing. This failure to improve the performance of antepartum monitoring appeared to result from prolonged accelerations, which complicated one third of the tests in which vibratory acoustic stimulation was employed. Further investigation is warranted using less profound methods of fetal stimulation.

Acoustic Stimulation↗
PubMed1990

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.

Female↗
PubMed1988

A review of the obstetric and medical complications leading to the delivery of infants of very low birthweight.

The delivery of very-low-birthweight infants is one of the major problems in human reproduction today. This study describes the principal obstetric and medical complications which led to the birth of 417 infants of 500-g to 1499-g birthweight, at the tertiary-level perinatal centre in Western Australia during the two years 1980 and 1985. An altered pattern of obstetric management of these cases was observed in 1985 compared to the management in 1980. In 1985, fewer deliveries were a result of spontaneous labour; tocolytic agents had been used in a smaller proportion of pregnancies; more infants were delivered by caesarean section without a preceding labour; and the still-birth rate was lower. Uncomplicated preterm labour was not the major cause of birth of very-low-birthweight infants. The most common factors that precipitated the delivery of very-low-birthweight infants were preterm premature rupture of the membranes (30% of cases), severe hypertension (19% of cases), antepartum haemorrhage (17% of cases) and preterm labour (17% of cases). Very low birthweight has a multifactorial aetiology, and its prevention will require a multidisciplinary approach.

Adult↗
PubMed1988

Nonstress and contraction stress fetal heart rate monitoring. A randomized trial to determine which is the faster primary test.

Antepartum fetal heart rate monitoring can be performed with either the nonstress or contraction stress method. The recent introduction of nipple stimulation as a means of achieving uterine contraction has simplified performance of contraction stress tests and raises the possibility that that test may be a more rapid approach to antepartum fetal heart rate testing than the nonstress test. In order to investigate the time taken to achieve a satisfactory end point of fetal heart rate monitoring, 186 women were randomized to either "intention to perform nonstress test" or "intention to perform nipple stimulation contraction stress test." Neither approach was found to be significantly faster than the other. One-third of all completed contraction stress tests were classified as equivocal and required further investigation or management. The nipple stimulation contraction stress test was not found to be a more rapid approach to antepartum fetal heart rate monitoring than the nonstress test.

Female↗