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This dissertation, Application of Ultrasonography in Early Pregnancy by Min, Chen, 陳敏, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: M Chen Abstract of thesis entitled APPLICATION OF ULTRASONOGRAPHY IN EARLY PREGNANCY Submitted by Chen Min for the degree of Doctor of Philosophy at The University of Hong Kong in June 2006 With the continuous technological improvement of obstetric ultrasonography, the number of fetal anomalies detected in the first and early second trimester continued to increase. This thesis summarizes the original research findings of the effectiveness of high resolution ultrasonography for screening fetal structural abnormalities in early pregnancy, and the evaluation of new technology (3-dimensional imaging) in feto-placental volumetric study. In an observational study involving a total of 1604 high risk women including 1599 singletons and 5 pairs of twins, the detection rate for structural abnormalities in the first trimester was 53.8 % (95% CI 44-64). The overall detection rate of structural M Chen abnormalities in the first and second trimester was 76.9% (95% CI 68.6-85.2). In a randomized control trial involving 7757 women from an unselected population, the detection rate of abnormality in the first trimester was 47.6% (95% CI 34.9-60.6), while the overall detection rate of abnormality in the first and second trimester was 66.7% (95% CI 53.7-78) in the study group (detailed 12-14 week scan followed by routine 18-23 week scan). The corresponding figures for the control group (11-14 week nuchal scan followed by routine 18-23 week scan) were 32.8% (95% CI 21.6-45.7), 64.1% (95% CI 51.1-75.7), respectively. There was no significant difference between two groups (P>0.05). Both the observational study in the high-risk population and the randomized control trial in the unselected population showed that the effectiveness of ultrasound examination at 12-14 weeks to screen for fetal abnormalities approached that achieved at 20 weeks and could be a good adjunct to the conventional examination. Our study also show that in centers where NT scan is offered, a detailed first trimester fetal morphology scan does not make any significant difference in the overall detection rate as well as the first trimester detection rate for fetal abnormalities in the general population. We confirm that it is possible to detect congenital abnormalities even with first-trimester nuchal translucency (NT) screening ultrasound in an unselected pregnant population. As a single scan at 12-14 week will not detect all fetal abnormalities, the conventional 18-23 week follow-up examination should ii M Chen always be performed. Three-dimensional ultrasound is a new imaging modality. Early fetal volume measurement by three-dimensional ultrasonography using the multiplanar technique and the rotational (VOCAL) technique was studied. The multiplanar technique appeared to be technically superior to VOCAL in measuring the fetal volume. We evaluated the use of placental volume measured by three-dimensional ultrasonography in predicting homozygous α -thalassaemia. It was demonstrated that assessment of placental volume did not seem to be superior to two-dimensional ultrasound in first-trimester prediction of homozygous α -thalassaemia. iii DOI: 10.5353/th_b3660331 Subjects: Fetus - Ultrasonic imagingPregnancy - Trimester, FirstThree-dimensional imaging in medicine

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