2.3 Pathogenesis of pre-eclampsia
Pre-eclampsia is proposed to progress in two stages.6 The first stage
involves inadequate development of maternal spiral arteries resulting
in deficiency in placental perfusion. The second stage involves widespread
endothelial dysfunction resulting in hypertension, proteinuria,
and oedema. Foetal perfusion is supplied by the maternal blood supply
through spiral arteries, which are terminal branches of radial arteries.
In normal pregnancies, the spiral arteries are invaded by trophoblastic
cellsthat replacethe endothelium of these arteries and promote remodelling
of the vascular wall with dilation of the blood vessels. In preeclampsia,
the placental invasion of these arteries is insufficient, resulting
in narrower blood vessels and hypoperfusion of the placenta. This placental
damage results in increased shedding of syncytial micro-particles
and other vascular toxins from the foetal unit into the maternal circulation
and is thought to contribute to stage 2 where there is generalized
endothelial dysfunction.6 Two anti-angiogenic proteins have been identified
that are overproduced by the pre-eclamptic placenta and gain
access to the maternal circulation and are the leading candidate molecules
responsible for the pre-eclampsia phenotype.4