Introduction and Objectives: In the current era of excellent surgical results for
congenital heart disease (CHD), focus has become directed on quality of life for
these children. Previous studies have shown that neurodevelopmental outcome in
CHD is impaired. The mechanisms are incompletely understood but there is
increasing evidence that the origins of this are in fetal life. This thesis aims to
describe the in utero brain growth in a cohort of fetuses with CHD and relate this to
the circulatory abnormalities and fetal Doppler parameters.
Methods: Pregnant women with a fetus with CHD were prospectively recruited. The
congenital heart defect was phenotyped using fetal echocardiography and patients
subdivided into three physiological groups on the basis of the anticipated abnormality
of cerebral blood flow and oxygen delivery: (1) isolated reduced flow to the brain; 2)
reduced oxygen saturation of cerebral blood flow; (3) combination of reduced oxygen
and flow. Fetal brain MRI was performed. In addition to standard biometric
measurements, snapshot to volume reconstruction (SVR) was used to construct a
3D data set from the oversampled raw data. From these 3D volumes the total brain
volume and ventricular volumes were measured by manual segmentation. Serial
measurements of fetal growth were also made and umbilical artery and middle
cerebral artery Doppler parameters were analysed.
Results: 29 women were included; comparison was made with 83 normal MRI
controls. Fetuses with CHD were found to have smaller brain volumes compared to
controls when adjusting for advancing gestation (p<0.01). This difference becomes
more pronounced with advancing gestation, suggesting a slower rate of in utero
brain growth. Measurements of growth found that the fetuses with CHD were smaller
throughout gestation with a highly significant difference at the later growth scan.
(p<0.001). Cerebral and umbilical artery Doppler data showed evidence of reduced
cerebrovascular resistance in fetuses with CHD but did not show a difference in the
umbilical artery Doppler.
Conclusion: Fetuses with CHD have evidence of impaired brain growth with
advancing pregnancy and an increased rate of overall growth restriction. Doppler
evidence of cerebral vasodilation supports the mechanism of reduced oxygen
delivery as an underlying cause.