Marfan syndrome
The risk of dissection increases with increasing aortic size; however, even patients with a normalsize
aorta 40mmmay be associated with up to a 10% risk of dissection [13]. Elective pre-pregnancy prophylactic
aortic surgery is recommended when the ascending aorta is >45 mm [14]. Surgery should also be
considered for aortas between 40 and 45 mm if there is a family history of dissection or evidence of
progressive dilatation. Beta blockers should be considered to limit the heart rate, prevent hypertension
and reduce the shear stress on the aorta. A mid-trimester non-contrast magnetic resonance imaging
(MRI) of the aorta is helpful to look for evidence of dilatation during pregnancy. Patients with a normal size
aorta may have a normal vaginal delivery. Patients with moderate aortic dilatation between 40 and
45 mm may have a vaginal delivery with a shortened second stage of labour. The recent guidelines
suggest elective caesarean section delivery for patients with an ascending aorta >45mm[14]: however,
assisted vaginal delivery with good regional anaesthesia and forceps lift-out to avoid maternal strain is
acceptable. Some patients have dural ectasia that may make epidural or spinal anaesthesia difficult or
impossible. Apart from the risks of aortic dissection, there is an increased risk of uterine rupture.