Pathophysiology of fetal intrauterine central shunts in high-risk pregnancies : a prospective observational Doppler study.
Year: 2009
Type: dissertation
Study design: Observational Study
Abstract: The primary objective of antenatal assessment and monitoring is to ensure wellbeing \nof the fetus and the mother. There are different methods of assessment during \npregnancy and in labour. Doppler ultrasound is one of the tests widely used in clinical \npractice in the evaluation of pregnancies that are at a greater risk of developing \nmaternal or fetal complications due to uteroplacental insufficiency. \nDoppler ultrasound enables evaluation of sequential changes in circulatory \nhaemodynamics in the fetus by evaluation of the fetus for signs of brain sparing and \nseverity of redistribution of circulation. Recognition of abnormal Doppler flow \npatterns helps the clinician to optimise the appropriate timing of delivery. \nIdentification of the ‘high risk’ fetus, before any changes of fetal compromise become \nevident, still remains one of the major dilemmas in contemporary clinical practice. \nThis thesis seeks to explore the role of Doppler monitoring fetal intrauterine central \nshunts as a method of identifying the ‘high-risk’ fetus before any other established \nparameters, such as, fetal biometry, fetal weight or flow waveforms in umbilical \nartery become abnormal. This thesis also evaluates the role of serial Doppler \nmonitoring of fetal central shunts in those fetuses where IUGR has been established. \nThis is based on the premise that the intrauterine shunts are present in fetal circulation \nto work closely with the placenta to ensure appropriate nutrition and oxygenation of \nthe fetus, bypassing the lungs. \nFour prospective longitudinal studies were designed to evaluate the role of fetal \nintrauterine shunts in adaptive response mechanisms in cardiovascular stress. Two \nmodels were taken into consideration: an ‘acute cardiovascular stress’ model and a \n‘chronic cardiovascular stress’ model. \nTo study the ‘response to acute cardiovascular stress’ in high-risk fetuses, a cohort of \nmothers undergoing fetal intrauterine transfusion for fetal anaemia were selected. \nThese fetuses were scanned immediately before and after transfusion, and Doppler \nflows through all the intrauterine shunts were documented and compared with \nfetoplacental and cerebral circulation. \nTo study the ‘response to chronic cardiovascular stress’, a prospective longitudinal \nobservational study was designed and the sequence of changes in Doppler ultrasound \nof the fetal central shunts studied and compared with the Doppler flow waveforms of normal pregnancies with a group of pregnancies complicated by uteroplacental \ninsufficiency. \nNormograms were designed for all the Doppler parameters and flows from adverse \npregnancy outcomes were compared to the normogram. \nThe pregnancy outcomes in the longitudinal study were correlated with placental \npathology. \nOur study showed that although changes were demonstrated in the flow patterns \nwithin central shunts, these changes were not statistically significant in the ‘acute \ncardiovascular stress model’, suggesting that there may be other haemodynamic \nalterations in acute cardiovascular stress. \nHowever, in the ‘chronic cardiovascular stress model’, the results suggest that the \nintrauterine cardiac shunts may play an important role in redistribution of fetal flows \nin early stages of growth restriction, suggesting that Doppler ultrasound monitoring of \nforamen ovale can be potentially used as a screening tool to identify high-risk fetuses \nas early as 16 weeks.
Author: Nayana Parange
Language: English
Subfield: Obstetrics and Gynecology
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W792771970