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Biomedical subjects

C R Whitfield

Publications and source records attributed to C R Whitfield.

At least 19 recordsLinked to original sources
PubMed1990

Post-extrasystolic potentiation in a human fetus detected during measurement of systolic time intervals in labour.

Measurement of the pre-ejection period (PEP), a non-invasive index of cardiac function, was made in a human fetus with a disturbance of cardiac rhythm manifested by: (i) intermittent mechanically ineffective extrasystoles (ventricular premature beats) and (ii) pauses. The mean interval between the sinus beats before and following extrasystoles was virtually the same as that before and following pauses. The PEP was shortened at the first sinus beat following both extrasystoles and pauses, but to a greater extent following extrasystoles. The PEP was still shortened at the second sinus beat following extrasystoles, but prolonged at the same cardiac cycle following pauses. These data demonstrate that fetal cardiac post-extrasystolic potentiation was taking place and that this was due in part to inotropic potentiation of the post-extrasystolic beats. Inotropic potentiation of post-extrasystolic beats is due to a fundamental property of cardiac muscle relating frequency of stimulation to strength of contraction (the so-called 'force-interval' relationship). Our data present the first evidence, to our knowledge, that the inotropic state of the human fetal heart in vivo is modulated by this mechanism.

Cardiac Complexes, Premature↗
PubMed1990

Luteal phase deficiency: ultrasonic and biochemical insights into pathogenesis.

Serial ovarian ultrasound and daily assessments of plasma concentrations of pituitary and ovarian hormones were used to investigate ovarian function in 175 women with unexplained infertility. Their endocrine and ultrasound profiles were compared with similarly derived data from 43 normal volunteers. Fifty-one (29.1%) of the study group showed subnormal luteal phase rises in progesterone concentrations, described as poor progesterone surge (PPS) cycles. Within this group, 23 women (45.1%) demonstrated luteal cyst formation, a pattern not seen in any of the control cycles. High concentrations of follicle stimulating hormone (FSH) and reduced concentrations of oestradiol (E2) were observed in the follicular phases of the PPS cycles suggesting that the phenomenon is a product of abnormal follicular metabolism. An association of PPS with infertility exists, perhaps related to a combination of disturbances in the follicular micro-environment compromising oocyte quality, a failure of oocyte release, and impaired endometrial receptivity.

Adult↗
PubMed1990

Luteal cysts and unexplained infertility: biochemical and ultrasonic evaluation.

A prospective, controlled study of ovarian function using ovarian ultrasound and daily plasma hormone estimations (estradiol, progesterone [P], follicle-stimulating hormone [FSH], luteinizing hormone [LH]) was carried out on 175 spontaneously cycling patients with unexplained infertility. Forty-one (23.4%) demonstrated luteal phase cyst formation. In 21 cycles the dominant follicle reduced in size after the LH peak (cystic corpus luteum cycles), and in 20 no shrinkage was seen (luteinized unruptured follicles). Progesterone concentrations in the early luteal phase were significantly reduced in the luteinized unruptured follicle cycles. Elevation in plasma FSH was seen in the early follicular and luteal phases of both cyst forming groups and may be due to disturbances in ovarian metabolism. Follicular rupture is important for efficient P release by the corpus luteum.

Adult↗
PubMed1988

A comparison of AmnioStat-FLM with three established methods of assessing fetal lung maturity.

A new rapid test of fetal lung maturity (the AmnioStat-FLM) was compared with two currently available rapid tests and with 2-dimensional thin-layer chromatography (2-d TLC). Forty-nine specimens of liquor obtained within 72 h of delivery were assessed, 27 of which were contaminated with blood or meconium. The AmnioStat-FLM compared well with spectrophotometry, the shake test and with 2-d TLC. Only the Amniostat-FLM and the 2-d TLC were reliable in the presence of contamination. The results suggest that the AmnioStat-FLM is a reliable, rapid test and unaffected by the presence of contamination.

Amniotic Fluid↗
PubMed1986

The measurement of fetal systolic time intervals: lessons from ultrasound.

Fetal systolic time intervals (pre-ejection period, iso-volumetric contraction time and ventricular ejection time) can be measured using Doppler ultrasound to detect valve movements and the fetal ECG to indicate the onset of ventricular depolarisation. Continuous recordings of FSTI, fetal heart rate and uterine activity depict changes reflecting progressive cord compression and have the potential for providing improved differentiation of late and variable decelerations. However, the continual adjustment of the ultrasound transducer required to maintain a good signal limits the technique. Recent improvements in phono indicate that this may provide a useful alternative, provided that suitable signal-processing is developed.

Electrocardiography↗
PubMed1986

Perinatally related wastage--a proposed classification of primary obstetric factors.

Adapting Sir Dugald Baird's concept of primary obstetric causes of perinatal mortality, a revised clinico-pathological classification has been evolved to take account of new knowledge and developments, and to direct attention to potentially avoidable deaths and to where intensified efforts and investigation are needed. Categories highlighting the importance of intrauterine growth retardation, unexplained intrauterine death and spontaneous premature labour have been introduced, intrapartum hypoxia is separated from birth trauma, and infection again has its own category. Regular perinatal audit at one obstetric hospital, since 1979, has shown that the new system provides a workable and useful means for classifying not only perinatal deaths, but also late abortions, late neonatal deaths and perinatally related infant deaths. The rate of total perinatally related wastage, defined in this way, was almost twice that for perinatal mortality (22.8 compared with 11.9 per 1000 births). The former is advocated as a more realistic index for the audit of perinatal care. The revised and extended system is put forward as a contribution to the current debate on classifying and reporting such wastage, in the hope that it may be tested as a model for regional as well as hospital surveys.

Birth Injuries↗
PubMed1985

Maternal serum alpha-fetoprotein in twin pregnancies uncomplicated by neural tube defect.

The maternal serum alpha-fetoprotein concentration was measured between 16 and 20 weeks in 145 twin pregnancies in which neither fetus had a neural tube defect. When the maternal serum alpha-fetoprotein concentration was less than two multiples of the singleton median, pregnancy outcome was good; the extended perinatal mortality rate was 32.6/1000, mean birth weights for the first and second twins were 2507 and 2443 gm, respectively, and mean gestation at delivery was 36 weeks, 6 days. When the maternal serum alpha-fetoprotein concentration was greater than four multiples of the singleton median, the outcome was poor; the extended perinatal mortality was 400/1000, mean birth weights were 1963 and 1523 gm, and mean gestation at delivery was 32 weeks, 4 days. The negative correlations of maternal serum alpha-fetoprotein concentration with birth weight and gestation at delivery were highly significant. Maternal serum alpha-fetoprotein concentration in midpregnancy is a useful predictor of outcome in twin pregnancy, independent of the occurrence of neural tube defect, and it appears to be related to the timing of delivery rather than fetal growth.

Birth Weight↗
PubMed1985

Significance of raised maternal serum alpha-fetoprotein in singleton pregnancies with normally formed fetuses.

One hundred eighty-six pregnancies with elevated maternal serum alpha-fetoprotein (AFP) between 16 and 20 weeks' gestation, but with normally formed single fetuses, were analyzed retrospectively. In comparison with matched control subjects, there was an increased incidence of low birth weight, preterm delivery, intrauterine growth retardation, and other clinical complications, especially when maternal serum AFP was abnormally high on more than one occasion. These findings could not be explained by the occurrence of threatened abortion or the performance of amniocentesis. It is suggested that where maternal serum AFP screening for fetal neural tube defects is already established as a cost-effective routine procedure, the additional recognition of some pregnancies at very high risk of other, perinatal complications is of practical value. However, maternal serum AFP testing in the second trimester cannot be recommended as a cost-effective screening method for detecting low birth weight infants, having a sensitivity in this series of only 11%. Many (33%) of the low birth weight infants detected in this way were very small (birth weights less than 1.5 kg); 73% of the predicted preterm births were very premature (before 34 weeks of gestation), and 72% of the identified growth-retarded infants were severely effected (weighing less than the fifth percentile for gestational age).

Abortion, Threatened↗
PubMed1984

Screening for small for dates fetuses: a controlled trial.

In the hope of reducing perinatal risks associated with retardation of intrauterine growth a previously described two stage ultrasound screening schedule was evaluated by a controlled trial in 877 women with low risk single pregnancies. The two stages of ultrasound examination were an assessment of gestational age during early pregnancy followed by measurement of length from crown to rump and area of trunk at between 34 and 36 weeks' gestation. The product of crown to rump length and trunk area was calculated. The sensitivity of this schedule in identifying in advance 94% of babies who were small for dates at birth, with 90% specificity, and the speed and simplicity of measurement confirmed the accuracy and feasibility of two stage ultrasonography as a screening procedure. The controlled trial did not, however, show any benefit from its routine application in these low risk pregnancies.

Adult↗
PubMed1984

Product of fetal crown-rump length and trunk area: ultrasound measurement in high-risk pregnancies.

Calculation of the product of crown-rump length and trunk area (CRL x TA), as measured by ultrasound between 34 and 36 weeks and combined with accurate assessment of gestational age in early pregnancy, was previously shown to be highly effective in detecting the small-for-dates fetus in a largely unselected series of patients. To assess the value of this two-stage schedule in high-risk pregnancies, 202 patients with singleton pregnancies at risk of fetal growth retardation were studied. Of the 53 babies that were small-for-dates at birth, 49 (92%) were identified in advance by CRL x TA measurement. In contrast to previous findings, measurement of trunk area (TA) alone was similarly effective, identifying in advance 48 (91%) of these small-for-dates babies.

Anthropometry↗
PubMed1984

Prenatal diagnosis. Amniocentesis.

Is amniocentesis safe? Does it still have a place in prenatal diagnosis? These questions continue to be asked, but it remains the cornerstone of diagnosis while other methods are being evaluated.

Abortion, Spontaneous↗
PubMed1983

HPLC of phospholipids in biological fluids -- application to amniotic fluid for the prediction of fetal lung maturity.

Because of both the advantage of speed compared with thin layer chromatography (TLC) and the dearth of high pressure liquid chromatography (HPLC) methods for phospholipid separation, it was decided to investigate the use of HPLC with a differential refractometer as detector for the separation and quantitation of amniotic fluid phospholipids required for the prediction of fetal lung maturity. A method was devised which gave results which compared well with those from TLC both in terms of quantitation and predictive value. Despite this, the method was found to lack sufficient reliability for application to the routine clinical assessment of fetal lung maturity. The method does, however, offer a good alternative to two dimensional TLC with phosphate analysis in research work involving quantitation of phosphatidyl inositol, phosphatidyl glycerol and particularly lecithin.

Amniotic Fluid↗