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M B McNay

Publications and source records attributed to M B McNay.

At least 19 recordsLinked to original sources
PubMed1999

Forty years of obstetric ultrasound 1957-1997: from A-scope to three dimensions.

In this article, we record the history of obstetric ultrasound as it developed worldwide in the second half of the twentieth century. The technological advances during this period saw the evolution of equipment from the original adapted metal flaw detectors producing a simple A-scan to the modern, purpose built, real-time colour flow machines with three-dimensional capability (Fig. 1). Clinically, ultrasound began as a research tool, but the poor quality of the images led to the ridicule of many of the early investigators. However, because of their perseverance, ultrasound developed into an imaging modality providing immense diagnostic capabilities and facilitating with precision many invasive procedures, diagnostic and therapeutic, both of which have made significant contributions to patient care. In this history, we recall the people, the personalities, and the problems they encountered during the development of ultrasound and how these problems were resolved, so that ultrasound now is available for use in the care of pregnant women throughout the developed world.

Embryonic and Fetal Development↗
PubMed1999

Prenatal diagnosis and management of nonimmune hydrops fetalis.

We examined the incidence, aetiological factors and outcome in 40 cases of nonimmune hydrops fetalis (NIH) and suggest a rational approach to management. The incidence of NIH was 1 in 830 deliveries during the last 10-year period. In spite of extensive antenatal and postnatal investigation no cause could be established in 14 (35%) cases. A probable aetiological factor was found in 65% of cases. These included viral infection (7), cardiovascular (6), twin-to-twin transfusion (3), chromosomal abnormality (3), other malformation syndromes (4), renal dysplasia (1), laryngeal atresia (1) and severe fetomaternal haemorrhage (1). Five of the 40 fetuses survived, 2 treated antenatally for tachyarrhythmia, 2 had spontaneous resolution and the fifth fetus had repeated intrauterine transfusions because of human parvovirus B19-induced anaemia. After diagnosis of nonimmune hydrops fetalis, early referral to a tertiary centre is to be encouraged for investigation and provision of intensive perinatal care. Investigation allows parents to be counselled appropriately that the mortality is no longer 100% and a steadily growing number may be amenable to some form of fetal therapy.

Adolescent↗
PubMed1998

First-trimester growth and the risk of low birth weight.

BACKGROUND: Previous studies have demonstrated a correlation between first-trimester size and birth weight. It is not known, however, whether low birth weight is related to first-trimester growth. We sought to determine whether the risk of low birth weight and birth weight that was low for gestational age is related to the size of the embryo or the fetus in the first trimester. METHODS: From a data base of ultrasound records of more than 30,000 pregnancies, we identified women who had no important medical problems, a normal menstrual history, and a first-trimester ultrasound scan in which the crown-rump length of the embryo or fetus had been measured. We examined the relation between the outcome of 4229 pregnancies and the difference between the measured and the expected crown-rump length in the first trimester, expressed as equivalent days of growth. RESULTS: A first-trimester crown-rump length that was two to six days smaller than expected was associated with an increased risk (as compared with a normal or slightly larger than expected crown-rump length) of a birth weight below 2500 g (relative risk, 1.8; 95 percent confidence interval, 1.3 to 2.4), a birth weight below 2500 g at term (relative risk, 2.3; 95 percent confidence interval, 1.4 to 3.8), a birth weight below the fifth percentile for gestational age (relative risk, 3.0; 95 percent confidence interval, 2.0 to 4.4), and delivery between 24 and 32 weeks of gestation (relative risk, 2.1; 95 percent confidence interval, 1.1 to 4.0), but not with delivery between 33 and 36 weeks (relative risk, 1.0; 95 percent confidence interval, 0.7 to 1.5). CONCLUSIONS: Suboptimal first-trimester growth may be associated with low birth weight, low birth-weight percentile, and premature delivery.

Birth Weight↗
PubMed1997

The relation between fetal abdominal circumference and birthweight: findings in 3512 pregnancies.

OBJECTIVES: To establish the relation between fetal abdominal circumference and birthweight in a large population of fetuses; to identify whether the error in estimating birthweight by abdominal circumference varied with the magnitude of abdominal circumference; and to establish whether adding femur length to abdominal circumference caused a clinically important reduction of error in predicting birthweight. DESIGN: A retrospective study. SETTING: The ultrasound department of a teaching maternity hospital offering a tertiary referral service. SAMPLE: From 3512 nondiabetic women with a normally formed singleton fetus, an abdominal circumference measurement of the infant was made within seven days of delivery; of these, 1213 had a femur length measurement performed at the same time. RESULTS: There was a linear relation between abdominal circumference and birthweight. There was a strong inverse correlation between the proportional error in predicting birthweight from the abdominal circumference and the magnitude of the abdominal circumference. Both the Campbell and Wilkin equation (abdominal circumference alone) and the Hadlock equation (abdominal circumference and femur length) were associated with systematic errors, especially with larger birthweight infants. The median absolute errors for the two equations were not significantly different overall (6.98% and 6.86% respectively), although the Hadlock equation was significantly more accurate in predicting birthweight in infants weighing greater than 4500 g. However, no threshold value of abdominal circumference or of estimated fetal weight using the Hadlock equation had a positive predictive value in estimating infants of > 4500 g of greater than 35%. CONCLUSIONS: Prediction of birthweight should be by abdominal circumference alone. Table 1 presents robust estimates of the error of predicting birthweight using fetal abdominal circumference.

Abdomen↗
PubMed1994

Midtrimester chorionic villus sampling: an alternative approach?

OBJECTIVE: Our purpose was to audit midtrimester chorionic villus sampling after a positive maternal serum screening test for autosomal trisomy. STUDY DESIGN: From January 1990 until July 1993 chorionic villus sampling was offered to all screened positive women. RESULTS: Five hundred fifty-one mothers had chorionic villus sampling. The mean age was 31.7 years. The mean gestational age was 18.2 weeks. The mean time for direct karyotyping was 4.4 days and for culture results 20.2 days. Results were obtained in 99.6% of samples: direct plus culture results in 94%, direct results alone in 2.3%, and culture results alone in 3.3%. Fourteen pregnancies had abnormal karyotypes. There were five cases of placental mosaicism and one false-positive result. The loss rate was 0.4%. CONCLUSION: Midtrimester chorionic villus sampling, which is easier to perform than cordocentesis, provides a rapid and reliable karyotype. The complication rate is comparable to that of other invasive procedures.

Adult↗
PubMed1993

Prenatal diagnosis and management of anterior abdominal wall defects in the west of Scotland.

An attempt was made to identify all the cases of abdominal wall defects occurring in the West of Scotland over a 7-year period to determine the current incidence, prenatal diagnosis, management, and prognosis for fetuses and neonates with abdominal wall defects. Cases were identified because they presented either for prenatal diagnosis, or to the Department of Pathology following termination or spontaneous pregnancy loss, or as neonates to the Neonatal Surgical Department. The incidence of abdominal wall defects was found to be 1 in 2500 births. Exomphalos was diagnosed before birth in 66 per cent of cases, and in 30 per cent of cases it was associated with another major abnormality. There was a 20 per cent intact survival in the cases diagnosed prenatally who had no fetal anomaly and who opted to continue with the pregnancy. Gastroschisis was diagnosed before delivery in 70 per cent of cases, and in the group who continued with the pregnancy there was an intact survival of 77 per cent. Body stalk anomalies were all diagnosed prenatally and terminated. Maternal serum alpha-fetoprotein was elevated in 89 per cent of the cases with exomphalos and in 100 per cent of the cases with gastroschisis and body stalk anomalies in which it was tested.

Abdominal Muscles↗
PubMed1991

Atrial natriuretic peptide: a vasodilator of the fetoplacental circulation?

Paired maternal and fetal atrial natriuretic peptide concentrations were measured in 62 percutaneous umbilical blood samplings performed principally for the assessment and treatment of rhesus isoimmunization. Pretransfusion fetal atrial natriuretic peptide levels were significantly higher than maternal atrial natriuretic peptide levels (median 117 pg/ml vs median 32 pg/ml; p less than 0.001); paired pretransfusion fetal and maternal atrial natriuretic peptide samples showed a weak correlation with each other (R2 = 17%; p = 0.002). Fetal atrial natriuretic peptide levels correlated inversely with hematocrit (R2 = 14%; p = 0.003), but not with albumin or gestational age. Paired pretransfusion and posttransfusion (median = 134 pg/ml) fetal atrial natriuretic peptide levels (n = 38) showed a significant rise after transfusion (p less than 0.001); this rise was related to the percentage of fetoplacental blood volume transfused (R2 = 33%; p = 0.035). In a subgroup of 26 procedures, change in fetal atrial natriuretic peptide levels was weakly correlated with transient reductions in the Doppler systolic/diastolic ratio of the umbilical artery (R2 = 14%; p = 0.07). These data support work in animals that indicate a role for atrial natriuretic peptide in the human fetus, but these data do not confirm that atrial natriuretic peptide modulates fetoplacental vascular impedance in the human fetus.

Atrial Natriuretic Factor↗
PubMed1991

Ultrasound detection of neural tube defects in patients with elevated maternal serum alpha-fetoprotein.

We conducted this study to determine the accuracy of ultrasound in the prenatal diagnosis of neural tube defects in women with elevated maternal serum alpha-fetoprotein (MSAFP). Among 905 pregnancies, 49 neural tube defects were correctly diagnosed by ultrasound alone; one was not. Ultrasound scanning had 98% sensitivity and 100% specificity for the detection of neural tube defects. The predictive value of a positive ultrasound diagnosis was 100% and of a negative ultrasound 99.9% for neural tube defects. Forty-three other structural abnormalities were also detected in patients with elevated MSAFP, including 19 abdominal wall defects, seven chromosomal abnormalities, five urinary tract abnormalities, one cardiac abnormality, and 11 others. Two chromosomal abnormalities were not detected. We suggest that ultrasound can be used reliably to detect neural tube defects, thereby avoiding the risks of amniocentesis.

Female↗
PubMed1990

Prenatal diagnosis of an intra-abdominal sacrococcygeal teratoma.

The prenatal diagnosis of a presacral (type IV) sacrococcygeal teratoma (SCT) is described. The initial ultrasound appearance was suggestive of a lower urinary tract obstruction, but further ultrasonic examination and radiological imaging using contrast medium led to the diagnosis of SCT. This is the first prenatal diagnosis of a totally intra-abdominal SCT.

Adult↗
PubMed1990

Rh haemolytic disease: continuing problem of management.

Eighteen patients with severe Rh haemolytic disease, all of whom underwent fetal blood sampling and intrauterine transfusion, were studied. Twelve babies survived (67%) all of whom were delivered by lower segment caesarean section. There were three intrauterine deaths resulting in late abortion, one stillbirth with trisomy 21, and two neonatal deaths (both from severe prematurity). The traditional prognostic indicators were all inaccurate, and fetal blood sampling and measurement of the fetal packed cell volume were the most direct methods of assessing haemolysis. The progression of severe Rh disease is unpredictable, and we believe that all cases should be referred to specialist centres for advice or treatment.

Autoantibodies↗
PubMed1989

Value of antenatal diagnosis of abnormalities of the urinary tract.

OBJECTIVE: To assess the value of antenatal diagnosis of abnormalities of the urinary tract on ultrasonography. DESIGN: Retrospective study. SETTING: Two obstetric units in Glasgow. SUBJECTS: 62 Fetuses in which renal abnormalities were diagnosed on antenatal ultrasonography. INTERVENTIONS: Six fetuses had their bladders aspirated to determine renal function. Fifteen pregnancies were terminated on the basis of the findings on antenatal ultrasonography, and if possible necropsy was performed on the fetuses. In babies who were born alive the final diagnosis was made by postnatal ultrasonography, intravenous urography, radionuclide scanning, cystography, and, in those who died in the early neonatal period, necropsy. Neonates who were referred with a known obstructed kidney had nephrostomy or pyeloplasty. END POINT: Assessment of the value of antenatal diagnosis of renal abnormalities on ultrasonography for babies who had no clinical evidence of disease postnatally. MAIN RESULTS: Eighteen fetuses did not survive birth; the antenatal diagnosis was accurate in all 18. Of the 44 babies born alive, five had normal urinary tracts, in two of whom antenatal ultrasonography had probably indicated a false positive diagnosis. Fourteen babies died during the early neonatal period. Twenty five babies with renal abnormalities were followed up; the antenatal diagnosis was inaccurate for 10 of them, the commonest misdiagnosis being hydronephrosis for multicystic kidney and vice versa, and there was one false positive diagnosis. The initial clinical findings in 14 babies would have led to the early detection of a urological abnormality. In the 30 babies with no clinical evidence of disease the antenatal diagnosis was of definite value in eight, probable value in 15, and marginal value in seven. Overall, an accurate antenatal diagnosis was made in 46 of the 62 cases (74%); in 12 cases renal disease was detected but its specific nature was not determined; and in four cases the diagnosis was misleading. CONCLUSIONS: The overall value of antenatal diagnosis is that it indicates early termination of fetuses with fatal renal disease, prepares parents and medical staff for the likelihood of serious neonatal problems, and shows abnormalities of the urinary tract that may not be detected postnatally.

Abortion, Induced↗
PubMed1989

Obstetric aspects of prenatal diagnostic methods.

The vast improvements in ultrasound technology have proved to be an important starting point for invasive investigative procedures in obstetrics. These methods not only allow a more precise diagnosis to be made but also offer considerable scope for in utero therapy.

Congenital Abnormalities↗
PubMed1989

The effect of intravascular transfusion for rhesus haemolytic disease on umbilical artery Doppler flow velocity waveforms.

To test the hypothesis that an increase in fetal blood viscosity is associated with an increase in resistance to flow, the effect on Doppler flow velocity waveforms of percutaneous umbilical blood sampling and intravascular transfusion was studied in 20 patients undergoing a total of 35 procedures. All but four of the 22 transfusions were associated with a decrease in resistance to flow, as shown by a reduction in the umbilical artery systolic/diastolic ratio, and this also occurred on 10 of the 13 occasions when blood sampling only was performed. These findings suggest that acute changes in blood viscosity following intravascular transfusion are not associated with an increase in resistance to flow as assessed by Doppler velocimetry. Umbilical blood sampling per se may be associated with a humorally mediated reduction in placental vascular resistance to flow.

Blood Transfusion, Intrauterine↗
PubMed1988

Fetal movements.

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Arousal↗
PubMed1987

Second trimester prenatal diagnosis of the Jarcho-Levin syndrome.

The Jarcho-Levin syndrome (spondylothoracic dysostosis) is a rare autosomal recessive disorder characterized by a short neck, short trunk and a constricted thorax due to multiple rib and vertebral defects; other visceral malformations are occasionally present. Most cases die in infancy due to respiratory failure. In this report we describe two cases in one family from the United Kingdom. Prenatal diagnosis by ultrasound examination during the second trimester was successfully accomplished in the second case.

Abnormalities, Multiple↗
PubMed1987

Diagnostic ultrasonography.

The use of diagnostic ultrasound has contributed to the evaluation of the fetal condition in two ways--the detection of fetal abnormality and the assessment of fetal growth and development. Routine early pregnancy scanning enables most major structural anomalies to be detected and provides accurate gestational dating. Maternal serum alphafetoprotein screening complements ultrasound in identifying abnormalities, and may also be an indicator of a growth problem in later pregnancy. In high-risk pregnancies, or when growth retardation or acceleration is suspected, abnormalities should always be considered and investigations should include karyotyping. Fetal growth may be assessed by multiple parameters, including measurement of fetal head, trunk, limbs, and amniotic fluid volume, in addition to grading of the placenta. Fetal responses to stimulation can be visualized and quantified. No single parameter may be used alone to predict fetal outcome, but by using this multiple-parameter approach, contributing to a biophysical profile of the fetus, the outcome of pregnancy may be predicted with greater accuracy.

Congenital Abnormalities↗