The Role of Obstetric Ultrasound in the Assessment of Fetal Growth and Development

Al-Bassam, Sabah (1990) The Role of Obstetric Ultrasound in the Assessment of Fetal Growth and Development. MSc(R) thesis, University of Glasgow.

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Abstract

Diagnostic ultrasound was introduced into obstetrics by Donald in the late 1950's and since that time has played an increasingly important role in the characterisation of normal fetal growth and the detection of intrauterine growth retardation. As a group intrauterine growth retarded fetuses have a high incidence of perinatal mortality and morbidity, and, in the long term, a higher incidence of neurological and intellectual impairment. Therefore, the antenatal detection of this group is desirable to permit careful monitoring and delivery at the optimal time, under the optimal circumstances. The objectives of this thesis were therefore to study the role of obstetric ultrasound in: (1) the determination of birthweight for gestational age growth standards which were displayed for all women with singleton live births, attending The Queen Mother's Hospital (QMH) antenatal clinic from 1985 to 1987; (2) the detection of intrauterine growth retardation (IUGR) by evaluating the effectiveness of seven single ultrasound measurements and two of their combinations . The association of fetal growth retardation with perinatal mortality and congenital malformation was also studied. In pursuit of the first objective a sample of 10259 births occurring in The QMH from 1985 to 1987 were analysed. Tables and curves were provided showing the means, standard deviations and 5th, 10th, 25th, 50th, 75th, 90th and 95th centiles of birthweight by gestational age for each week of gestation from 28 to 42 weeks. Tables and curves were classified according to the sex of the infant and parity of the mother. The sample was composed of singleton live infants born to women who had ultrasound dating of gestation prior to 20 weeks. This sample comprised 26% of all live birth in Greater Glasgow Health Board area and 5. 2% of all live births in Scotland during the study period. Similar analysis was repeated on a subset of 3919 births selected from the above sample. Women included in this group had to meet a number of criteria in order to minimize the effect they might have on the distribution of birthweight for gestational age. These criteria were: (1) their babies were without congenital malformation; (2) spontaneous onset of labour; (3) not on the contraceptive pill for the three months before pregnancy; (4) certain date of last menstrual period; (5) gestational age confirmed by ultrasound prior to 20 weeks. The QMH based standards were then compared with a number of growth standards reported for other populations, including the widely adopted standards of Thomson and associates (1968) for Aberdeen 1948-64 and Forbes and Smalls (1982) for Scotland 1975-79. The QMH based standards were comparable to the previous Scottish standards and slightly higher later in pregnancy. Similarly the 10th centile values were comparable with Scotland 1975-79 (Forbes & Smalls, 1982), but beyond 38 weeks of gestation they were significantly higher. In contrast to previous growth standards, the QMH based standards were obtained from a group of women with accurate ultrasound dating early in pregnancy. These results would justify a further study based on a large population to establish a proper growth standard. Nevertheless, tables and curves will be a useful guide for the birthweigh monitoring of infants born in the QMH. Other variables such as sex of the infant and parity of the mother were also examined in relation to birthweight. Male infants were heavier than females and infants of multiparae were heavier than infants of primiparae. In pursuing the second objective, a total of 14791 consecutive ultrasound measurements of 2810 women with singleton pregnancies, were analysed. All pregnancies were dated before the 20th week by ultrasonic measurements and had a second ultrasonic examination between 28 and 36 weeks of gestation to permit measurements of 7 single measurements and 2 of their combinations to detect those fetuses whose birthweights were below the 10th centile line on the Scottish standards 1975-79 (Forbes & Smalls, 1982). The measurements of biparietal diameter (BPD), head area (HA), head circumference (HC) , abdominal area (AA), abdominal circumference (AC) femur length (FL), amniotic fluid volume (LV), abdominal area x femur length (AAFL) and abdominal circumference x femur length (ACFL) were studied. The measurements below the 10th centile for gestational age were considered abnormal. Fetal head measurements had inferior predictive ability than abdominal measurements. The LV and FL measurements proved to be the least sensitive indicators of IUGR. The combination of FL measurement with that of abdomen had markedly improved the diagnostic accuracy over that of single measurement of FL, AA or AC.

Item Type: Thesis (MSc(R))
Qualification Level: Masters
Keywords: Medicine, Obstetrics, Medical imaging
Date of Award: 1990
Depositing User: Enlighten Team
Unique ID: glathesis:1990-78137
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 30 Jan 2020 15:39
Last Modified: 30 Jan 2020 15:39
URI: http://theses.gla.ac.uk/id/eprint/78137

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