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Title: Development of placental ultrasound markers to screen for the term 'small for gestational age' (SGA) baby
Author: Collins, Sally L.
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2012
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Fetal growth restriction is the largest single risk factor for stillbirth, one of the biggest issues in modern day obstetrics. This study aimed to identify ultrasound markers to aid the development of a screening test for growth restriction. Data were acquired from 143 pregnancies. Of these; 113 were normotensive and delivered appropriate for gestational age (AGA) babies at term; 13 women were normotensive with term small for gestational age (SGA) babies, five were hypertensive with term SGA babies and two had pre-term SGA babies. A technique examining the jet of blood from the mouth of the spiral artery (SA) is described and validated. As predicted histologically in the literature, the size of the SA mouth increased, and the jet pulsatility decreased, with advancing gestation. The waveform developed differently in SGA pregnancies. The study also describes the novel observation of mega-jets, a potential surrogate marker for placentation. Only before 14 weeks' gestation could the whole placental volume be reliably captured in a single sweep. A novel semi-automated method for generating placental volume (PlaV), total surface area and area of the basal plate was used in a study for the first time. The dimensionless standardized placental volume (sPlaV) was explored and shown to predict SGA, independent of PAPP-A. A model developed by combining sPlaV and PAPP-A performed well, especially in a low risk population, (50% sensitivity for a 10% false positive rate). The 3 dimensional (3-D) power Doppler data gathered in this study enabled the effect of gain on calculated Virtual Organ Computer-aided AnaLysis II (VOCAL II™) indices to be examined in vivo. This suggested that the use of the sub-noise gain setting might help to standardise the information gained for each subject, which should improve between patient comparisons. We conclude that the development of a screening test for SGA including sPlaV may be possible. Development of other markers may further improve the test. This should ensure appropriate antenatal care for 'at risk' pregnancies whilst keeping the normal ones, 'normal'.
Supervisor: Impey, Lawrence ; Noble, Alison Sponsor: NIHR via Oxford Biomedical Research Centre (BRC)
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Obstetrics ; Medical Sciences