Steyn, Clare Elizabeth; (1997) Interaction between fetal and neonatal growth and blood pressure development. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

There is much debate concerning the influence of nutrition in utero on fetal and neonatal growth and development. Recent epidemiological studies have suggested that nutritional influences acting during intrauterine and early postnatal life may have long term consequences for cardiovascular disease. More specifically, the suggestion has been made that small babies born with a large placenta are predisposed to hypertension in later life. Thus, there would appear to be important links between fetal nutrition, and thus growth, and cardiovascular disease in adult life. The availability of nutrients is essential for fetal growth. Whilst there is obviously a relationship between maternal nutrition and nutrient supply to the fetus, the placenta is another major determinant of nutrient availability. The metabolic and endocrine interactions that occur between fetus, placenta and mother have important regulatory effects on fetal growth. The work described in this thesis was undertaken with the aim of trying to establish more clearly the mechanisms by which fetal and neonatal nutrition and growth influence blood pressure development. The role of oxygen availability to the fetus was studied using two models, anaemia and repeated acute hyoxaemia. The role of nutrient availability was studied by altering maternal nutrition in early pregnancy. I have investigated the development of blood pressure and cardiovascular reflexes in relation to fetal and neonatal size and growth, placental size, endocrine status, and maternal nutritional plane. The results of this work show that there is a link between postnatal blood pressure and maternal nutritional anaemia during pregnancy, and that there is also an important association with the rate of postnatal growth. Postnatal blood pressure may relate to blood pressure development during fetal life. So, it was interesting to find that mean arterial blood pressure (MAP) follows distinct trajectories in individual fetuses and fetal chemo- and baroreflexes are also altered. Chronic fetal hypoxaemia may be an important factor in the aetiology of adult hypertension, however, two weeks of repeated acute hypoxaemia during late gestation does not affect cardiovascular development and periconceptual maternal undernutrition does not result in hypoxaemia during late gestation. Nevertheless, fetal cardiovascular development during late gestation is perturbed by periconceptual undernutrition, an effect that may be the result of alterations in placental function. These effects on fetal cardiovascular development in relation to oxygen, nutrient supply and maternal nutrition, and their interaction with fetal growth, have important implications for understanding the processes of cardiovascular development in health and disease.

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