Biomedical subjects
P S Warren
Publications and source records attributed to P S Warren.
The significance of high umbilical venous blood flow measurements in a high-risk population.
We report a statistical analysis of 893 high-risk patients who underwent Doppler sonographic estimation of umbilical venous blood flow within 2 weeks of delivery. Patients with red cell isoimmunization were excluded. In a total of 84 patients, the umbilical venous flow rate was above the 95th centile for normal pregnancy. This finding was associated significantly with an increased prevalence of maternal diabetes mellitus, polyhydramnios, fetal abnormalities, premature delivery, low 5 min Apgar scores, and neonatal death. Umbilical venous flow rates per kilogram of fetal weight above the 95th centile were recorded in 93 patients. This finding was associated significantly with an increased rate of antepartum hemorrhage, premature delivery, low 5 min Apgar scores, longer stays in intensive care nursery, and neonatal death. Low umbilical venous blood flow rates have been investigated extensively and associated with impaired perinatal outcome. The work reported in this paper indicates that a percentage of fetuses will have abnormally high umbilical venous flow rates and that this is also indicative of increased risk.
Volume imaging: three-dimensional appreciation of the fetal head and face.
Quasi-three-dimensional volume imaging provides an inexpensive means of evaluating the usefulness of three-dimensional imaging. The technique works most efficiently with water-skin interfaces and therefore we investigated its application in obstetrical ultrasonography. Three-dimensional perspectives of the normal and abnormal fetal head and face were spectacular and at times provided more information than the two-dimensional images. The ability of an inexperienced observer to interpret the three-dimensional image more easily may have a role in training sonographers and counseling parents whose fetuses have structural defects. Volume imaging has certain limitations and can only be used as a complementary technique.
Real-time quasi-three-dimensional viewing in sonography, with conventional, gray-scale volume imaging.
Real-time three-dimensional views of the fetus can be obtained with minor modification to conventional scanners. The modification consists of placing a divergent lens in the out-of-scan plane of the transducer to generate a beam fan-beam in the insonated volume. All of the echoes from which insonates a volume rather than a slice of tissue. Scanning is performed using oblique angles of incidence to provide total reflection conditions. Echoes are then received only from anterior surfaces, automatically generating the three-dimensional views. Intriguing portrayal of fetal detail can be obtained with this form of imaging which is likely to expand the clinical utility of sonographic examinations.
Thickness of tissues intervening between the transducer and fetus and models for fetal exposure calculations in transvaginal sonography.
In transvaginal scanning the tissues intervening between the fetus and transducer are relatively thin. The average thickness in the first trimester is 25 mm and reduces to 15 mm by the third trimester; the minimum thicknesses are 14 and 8 mm, respectively. Two models are proposed for calculating exposure in transvaginal scanning. The models are considered in terms of the overlying tissues and the target tissues. A fixed path, constant attenuation of 0.3 dB/MHz describes the properties of the overlying tissues throughout pregnancy. In the model used in first-trimester scanning, the target tissues of the embryo/fetus are considered to have properties similar to those of soft tissues, and they attenuate the energy at the same rate as the overlying tissues. In the model used in second- and third-trimester scanning, the bony structures of the fetus are the target tissues. These reflect 30% of the incident energy and attenuate all of the transmitted energy at their surface.
Early growth retardation in the first trimester: is it characteristic of the chromosomally abnormal fetus?
There have been recent reports on a small number of cases which suggest that the detection of early growth retardation might allow recognition of the chromosomally abnormal fetus in the first trimester of pregnancy. To amplify these observations, the crown-rump length (CRL) measurements between the 64th and 86th day of menstrual age were determined in (a) 500 control high risk patients in whom a normal karyotype was subsequently demonstrated by chorionic villus sampling (CVS) and (b) 25 chromosomally abnormal fetuses. The data indicate that early growth retardation, as expressed by a small CRL measurement, is not a special characteristic of the chromosomally abnormal fetus in the first trimester of pregnancy. The CRL measurement is therefore not a useful marker or screening test at that time, except perhaps for triploidy. The well documented growth retardation with trisomy 21 and trisomy 18 which has been observed in the second trimester does not begin until after the 12th week of menstrual age.
Completed follow-up of 1,000 consecutive transcervical chorionic villus samplings performed by a single operator.
Completed follow-up data on 1,000 patients undergoing transcervical chorionic villus sampling (CVS) performed by a single operator at the Royal Hospital for Women is presented. Prior to the introduction of CVS, approximately 750 amniocenteses were performed annually in this unit. Over the past 5 years the total number of patients having CVS or amniocentesis has increased by 1/3 and almost 1/2 of procedures are now done by CVS. We have persisted with the transcervical route believing that once the learning curve is past, this route compares favourably with the transabdominal method in loss rate and perinatal outcome. We feel the transcervical approach is better tolerated by our patients and that less procedural difficulties are encountered. With increasing operator experience the total fetal loss rate to 20 weeks' gestation in our series declined to 2.1% and late complications were no more frequent than expected. In 98.4% of patients, sufficient villi were obtained for analysis. Culture failure was extremely uncommon, occurring only twice in our series. In 1.5% of patients, a follow-up amniocentesis was required, which compares favourably with other published series. It appears that many units abandoned the transcervical route before loss rates were stabilized. In units where transcervical CVS is still performed the transabdominal route is also utilized. The reverse is not true. The authors feel that both procedures have a role in modern antenatal diagnosis.
Transvaginal pulsed Doppler ultrasound assessment of blood flow to the corpus luteum in IVF patients following embryo transfer.
The waveforms of vessels supplying the ovaries of women on an in-vitro fertilization (IVF) programme were studied using transvaginal B-mode and Doppler ultrasound. There were 125 scans recorded in 65 women at weekly intervals from 3 days after embryo transfer or 5 days after gamete intrafallopian transfer (GIFT) until confirmation of pregnancy or onset of menses. At each examination the signals obtained from vessels supplying the ovaries were recorded and quantified using a resistance index (RI). Fifteen patients became pregnant of whom one has subsequently miscarried. There was a highly significant difference in the RI values between patients who became pregnant and those who did not; no patient who became pregnant had a RI greater than 0.5. Oestrogen to progesterone ratios were calculated in the subgroup of non-pregnant patients and there was no correlation between these values and the RI values. This new technique enables prediction of IVF treatment failure earlier than has been reported previously and may reflect the inadequacy of the corpus luteum.
Doppler flow studies in rhesus isoimmunization.
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Chorionic villus sampling. Clinical experience in 50 diagnostic cases.
The results of 50 diagnostic chorionic villus samplings (CVS) are presented. In all but 2, the fetus was at risk of a chromosomal abnormality. Sampling was successful in 48 cases. One patient aborted 4 days after the procedure. Two patients had missed abortions diagnosed on ultrasound 44 and 56 days after CVS. Seven patients elected to have their pregnancies terminated. All samplings were undertaken with a specially designed cannula using realtime ultrasound guidance between 9 and 11 weeks of amenorrhoea. Endocervical swabs and blood for maternal serum alpha fetoprotein estimations before and after the procedure were routinely taken. All patients were notified of the results in 8 days or less except in 3 where long-term cultures were necessary. Six patients have delivered and 34 pregnancies are continuing satisfactorily.
Cloverleaf skull with generalised bone dysplasia. Report of a case with short review of the literature.
A case of cloverleaf skull with generalised bone dysplasia is reported. The authors believe that bone dysplasia associated with cloverleaf is neither identical with thanatophoric dysplasia nor achondroplasia. Until identity of thanatophoric dysplasia and cloverleaf skull with generalised bone dysplasia is proved the diseases should be looked upon as separate entities and the wording "thanatophoric dysplasia with cloverleaf skull" should be abolished.
Fetal lateral ventricles in the second trimester.
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Observations of fetal lung reflectivity using real-time ultrasound.
The ultrasonic appearance of the fetal lung alters as pregnancy progresses and this is expressed as increased reflectivity to ultrasound. Evidence is presented that demonstrates that these changes can be induced and that they may reflect increasing lung maturity.
The sleep and performance of shift workers.
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Fetal umbilical venous flow measured in utero by pulsed Doppler and B-mode ultrasound. I. Normal pregnancies.
Umbilical venous blood flow was measured with a pulsed Doppler unit, which was used in combination with a B-mode ultrasonic imaging system to permit location of the umbilical vein and measurement of its cross-sectional area. The accuracy and limitations of the method are discussed. Forty-seven normal fetuses with gestational ages ranging from 22 weeks to term were studied on a total of 61 occasions. Flow increased with gestational age until 36 weeks, was maximal between 37 and 38 weeks, then decreased during the last 2 weeks of pregnancy. Flow per unit of fetal weight was constant during pregnancy until 36 to 37 weeks, when a reduction occurred.
Ultrasonographic diagnosis of neonatal renal venous thrombosis.
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Early diagnosis of Meckel's syndrome.
Meckel's syndrome is a disorder of polygenic origin inherited as an autosomal recessive. The main features are microcephaly, occipital encephalocoele with associated midline facial defects, renal and limb anomalies. The diagnosis has previously been made ultrasonically by the repeated demonstration of small head size. In this instance a renal anomaly was demonstrated and use to confirm the diagnosis.
Cerebral ventricular size in children: a two-dimensional ultrasonic study.
The width of the bodies of both lateral ventricles was studied in 833 children using B-mode echography. It could be accurately measured in 99.9% of those under the age of 2, 94% of these 2 to 5, and 65% of those 6 to 12. The normal lateral ventricular ratio or LVR (width of body of LV/0.5 X internal skull diameter) was 0.24-0.36, but there was a borderline area and the upper part of this range (0.34-0.36) included some cases of early hydrocephalus. In 72% of the children with a head circumference greater than the 98th percentile, the LVR was 0.24-0.36. The greatest transverse diameter of the atrium of the normal lateral ventricle in children appears to be 10 mm, that of the normal third ventricle 5 mm. A water-delay system is described as being superior to a contact system for B-mode echoencephalography.