Systemic vascular resistance falls to 70% of its
preconception value by 8 weeks gestation due to
vasodilation, observed by a relative fall in maternal
blood pressure, especially noted by the diastolic
pressure (Gelson et al, 2006).
Pregnancy is a pro-arrhythmic state due to
increased levels of catecholamines and hormonal
changes. In women with complex structural heart
disease, uncontrolled arrhythmias can tip the
balance and lead to haemodynamic instability.