Biomedical subjects

J Newnham

Publications and source records attributed to J Newnham.

26 records · Page 2Linked to original sources

PubMed1995

Screening for the small fetus: a study of the relative efficacies of ultrasound biometry and symphysiofundal height.

In this study 3 different methods of screening for birth-weight < 10th percentile in pregnancy were evaluated both individually and in combination; 1,135 women with singleton pregnancies were studied. Measurements of symphysiofundal height by tape measure, and amniotic fluid index and fetal abdominal circumference by ultrasound imaging, were made at 18, 24, 28, 34 and 38 weeks. At none of these gestational ages did amniotic fluid index perform well as a screening test for birth-weight < 10th percentile. Combining the tests, using symphysiofundal height to select a group at high risk who then had a fetal abdominal circumference measurement, reduced the false positive rate but significantly decreased the percentage of infants diagnosed. The results of this study confirm that the most appropriate antenatal diagnostic test for birth-weight <10th percentile is ultrasound measurement of fetal abdominal circumference. Selecting pregnancies at risk by clinical measurement of symphysiofundal height will provide a lower false positive rate than a policy of performing ultrasound on all pregnancies during the third trimester, but will also reduce the sensitivity.

Adult↗

PubMed1995

Postnatal lung function in lambs after fetal hormone treatment. Effects of gestational age.

We previously found that a single dose of betamethasone in combination with thyroxine given by intramuscular injection to fetal sheep 48 h before preterm delivery at 128 d gestation improved postnatal lung function. We have now asked how the combination of 0.5 mg/kg betamethasone and 15 micrograms/kg T4 given by a single fetal intramuscular injection changes lung response 48 h after treatment at 121 and 135 d gestation. At 121 d gestation the fetal hormone treatment significantly improved postnatal lung function. Compliance increased by 55%, arterial PO2 increased from 39 to 215 mm Hg, PCO2 decreased from 109 to 79 mm Hg, and maximal lung volumes increased by 112%. The hormone treatment decreased the severity of the respiratory failure, although these very preterm lambs still had severe respiratory failure. At 135 d gestation, the fetal hormone treatment decreased the ventilatory pressure requirements that were needed to normalize PCO2 values from 30 to 21 cm H2O. Compliance increased by 40%, and maximal lung volumes increased by 33%. Alveolar or lung tissue, saturated phosphatidylcholine, or alveolar SP-A pool sizes did not change with hormone treatment at 135 d gestation. We conclude that fetal hormone treatment significantly improved postnatal lung function at both gestational ages, although the characteristics of the responses were different.

Animals↗

PubMed1993

Lung responses to ultrasound-guided fetal treatments with corticosteroids in preterm lambs.

Maternal corticosteroid treatments augment lung function in the human preterm infant. However, not all fetuses respond, the response requires > or = 48 h of exposure, and multiple maternal doses expose the mother to potential risks. To evaluate the potential of direct fetal therapy, we used ultrasound to direct fetal intramuscular or intravascular injections of corticosteroids or saline in sheep and subsequently delivered the preterm lambs at 128 days gestational age to assess postnatal lung function. Relative to saline-injected controls, 0.5 or 2 mg/kg betamethasone given as a single intramuscular dose 48 h before delivery increased compliance and the efficiency of ventilation (as measured by an indicator that included ventilatory pressures and CO2 values) nearly twofold (P < 0.05). Lung volumes, measured from deflation pressure-volume curves, also increased (P < 0.05). However, the 2 mg/kg dose caused severe pulmonary interstitial emphysema in 5 of 13 lambs, suggesting adverse effects. An intravascular fetal dose of 12.5 mg/kg hydrocortisone or an intramuscular dose of 0.1 mg/kg betamethasone had no effect on postnatal lung function. In separate studies, the 2 mg/kg dose improved all indicators of lung function almost twofold after only 24 h of fetal exposure and delivery at 128 days gestational age (P < 0.01). There was a dose-dependent suppression of the postnatal cortisol surge in treated animals, although fetal treatment did not alter cord cortisol levels. Single-dose fetal hormone treatments can cause large and rapid improvements in postnatal lung function in preterm lambs.

Adrenal Cortex Hormones↗

PubMed1992

The epidemiological characteristics of unexplained antepartum stillbirths.

All antepartum stillbirths weighing 1000 g or more born in Western Australia from 1980 to 1983 were categorised as 'unexplained' or 'explained' based on information from Perinatal Death Certificates. Using data from hospital and doctors' antenatal records a number of variables in each stillbirth category were compared by unconditional logistic regression. Significant differences were observed between the two groups in medical disorders and abnormalities of pregnancy, thus confirming our classification system. Compared with mothers of 'explained' antepartum stillbirths, mothers of unexplained antepartum stillbirths tended to have younger ages at delivery and had associated lower parity, more antenatal visits to the medical practitioner, fewer hospital admissions, a greater chance of having received care by a general practitioner than by a specialist obstetrician and were of more advanced gestation at the time of diagnosis. The results of this study indicate that the epidemiological characteristics of pregnancies resulting in unexplained antepartum stillbirths differ from those resulting in explained antepartum stillbirths. This suggests that unexplained antepartum stillbirths are not merely the result of inadequate obstetrical management but consist of a series of fetal disease states which are not currently amenable to detection.

Case-Control Studies↗

PubMed1992

A case-control study of unexplained antepartum stillbirths.

OBJECTIVE: To ascertain factors that will identify women who are at increased risk of unexplained antepartum stillbirth. DESIGN: Matched case-control study. The cases and controls were initially analysed as a whole group and again after dichotomizing into those of low birthweight (< 2500 g) and those of normal birthweight (> or = 2500 g). SETTING: Western Australia 1980-1983. SUBJECTS: Unexplained antepartum stillbirths of > or = 1000 g birthweight (cases) and liveborn infants individually matched for year of birth, plurality, sex and birthweight of infant and race of mother (controls). RESULTS: The case pregnancies had more polyhydramnios (OR 10.83, 95% CI 2.41-48.69) and cord problems (OR 6.57 95% CI 1.36-31.75) than the controls but, paradoxically, other obstetric and medical complications were less common in the cases. The association with polyhydramnios persisted when the analysis was confined to those with low birthweight. With normal birthweight fetal distress was more frequent in the cases (OR 3.65 95% CI 1.36-9.80) but there were few other differences. CONCLUSIONS: The clinical and diagnostic systems currently in use are unable to identify many fetuses at risk of death. Decreases in the rate of unexplained antepartum stillbirths await the discovery of new preventable causes, or of innovations in clinical or laboratory aspects of obstetric care.

Birth Weight↗

PubMed1990

The effect of heart rate on Doppler flow velocity systolic-diastolic ratios in umbilical and uteroplacental arterial waveforms.

In an analysis of the influence of heart rate on Doppler flow velocity waveform-systolic/diastolic ratios from 1555 umbilical artery waveform studies and from 1497 uteroplacental waveform studies, a negative correlation was observed between the ratio and the corresponding heart rate. This relationship was not influenced by gestational age and was similar in pregnancies with normal outcomes when compared with all pregnancies. The magnitude of this inverse relationship is such that the effect of heart rate on systolic/diastolic ratios must be considered when Doppler flow velocity waveform analyses are used as experimental tools to assess placental vascular resistance but it does not appear to be an important factor in general clinical practice when measurements are made during fetal inactivity and when heart rates are within normal ranges.

Blood Pressure↗

PubMed1988

Stillbirths in Western Australia 1980-1983: influence of race, residence and place of birth.

All stillbirths in Western Australia from 1980-83 weighing 1,000 g and over were identified from perinatal death certificates, and their causes and demographic correlates described. The stillbirth rate was 4.91 per 1,000 total births; nearly 65% were antepartum, 25% intrapartum and in 10% the time of death was unknown. The cause of death of most stillbirths was unknown (52%) or associated with lethal congenital malformations (13%), antepartum haemorrhage (12%) or maternal hypertension (8%). Whilst Aboriginal women had much higher stillbirth rates (10.80) than non-Aboriginal women (4.57), their patterns of time and causes of death were similar. Both antepartum and intrapartum stillbirth rates were much higher at low birth-weights and low gestational ages in both racial groups. Women living in rural areas who delivered in the metropolitan area had much higher antepartum (11.02) and intrapartum (3.31) stillbirth rates than either rural women delivering in rural areas (1.89 and 1.34) or metropolitan women delivering in the metropolitan area (2.72, 0.98). This reflects the transfer of rural high risk pregnant women or those with fetal death in utero, for delivery in metropolitan specialist hospitals.

Age Factors↗

PubMed1987

Effect of fetal thyroidectomy on newborn thermogenesis in lambs.

We investigated the effect of the transient neonatal hyperthyroid state on thermogenesis at birth by measuring rectal temperature, plasma free fatty acids, plasma catecholamines, and in vitro brown adipose tissue respiration in thyroidectomized (n = 6) and sham operated (n = 5) fetal sheep. Surgery was performed at an average of 133 days of gestation followed by cesarean delivery at 146 days. Fetuses were delivered into a constant room temperature of 25 degrees C. Serial measurements were made in utero before delivery and at timed intervals after birth. Serum 3,3',5 triiodothyronine and thyroxine concentrations in the neonatal period were normal in sham operated and nondetectable in thyroidectomized fetuses. Rectal temperatures and serum free fatty acid levels were reduced in thyroidectomized newborns. Plasma epinephrine concentrations were increased and the hypothyroid neonates were acidotic when compared to control animals. In vitro basal and norepinephrine stimulated brown adipose tissue respiration were reduced in thyroidectomized compared to control animals. These results indicate that thyroid hormone deficiency impairs nonshivering thermogenesis in brown adipose tissue and leads to hypothermia despite augmented plasma epinephrine values.

Adipose Tissue, Brown↗