In summary, there is no perfect management strat- egy for women with prosthetic heart valves. If the mother has a tissue prosthesis, reoperation is inevi- table eventually, with its attendant risks, but in high-volume surgical centers this risk should be low (<2%). Mechanical prostheses are more problematic than tissue prostheses during pregnancy, particularly mitral prostheses, and especially the older generation of valves in this position. Th ere is no perfect antico- agulant strategy and each approach has its own set of problems. Warfarin is associated with increased embryopathy and fetal loss, although less so when the dose is <5 mg daily. Since warfarin is a more eff ective anticoagulant than heparin in pregnancy, this may be the best alternative in women who are at higher risk of valve thrombosis. Alternatively, unfractionated heparin can be used in the fi rst trimester, although APTT monitoring must be meticulous and should be maintained at at least twice the control value.
Warfarin may be substituted at around 13 weeks of gestation but should be discontinued well in advance of anticipated labor.
LMWH does not cross the placenta and is a viable therapeutic alternative, particularly in women whose warfarin dose exceeds 5 mg daily because they have an increased risk of fetal embryopathy. If LMWH is used, meticulous anti-Xa monitoring is necessary to maintain 4 h postinjection anti-Xa levels at around 1–1.2 IU/ml. Once organogenesis in the fetus is com- plete and there is no risk of embryopathy, aft er the fi rst trimester it is probably preferable to discontinue hep- arin and substitute warfarin during the second and early third trimesters, changing back to unfractionated heparin well before delivery .
Adjunctive aspirin therapy in the second and third trimesters should be considered with any of the above regimens. Long-term anticoagulants should be resumed as soon as possible postpartum .
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Section 4: Antenatal Care: Specifi c Maternal Conditions
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Heart Disease and Pregnancy, 2nd edn. ed. Philip J. Steer and Michael A. Gatzoulis. Published by Cambridge University Press.
© Cambridge University Press 2016.
Chapter
Practical practice points
1. Aortic dissection is an important cause of maternal morbidity and mortality.
2. All women with known Marfan syndrome should be aware of the implications of pregnancy and should, if they wish, have access to expert prepregnancy advice.
3. Women with Marfan syndrome and an aortic root diameter of <40 mm should be reassured that the risks are less than that of a patient with a larger root. Th eir risk is on average about 1% for a dissection during or immediately aft er pregnancy.
Th e risk will be greater it there is a family history of aggressive aortic involvement. Women with a root diameter of ≥45 mm should be off ered elective root replacement before pregnancy; otherwise the risk of dissection may be as high as 10% .
4. Women with other aortopathy or an aortic root of diameter >40 mm should be aware of the increased risk of an adverse outcome. Th is risk increases with size, rapid rate of change, and a family history of dissection.
5. Beta-blockers should be off ered to patients with Marfan syndrome to slow the progression of aortic root dilatation. Furthermore, consideration should be given to continuing beta-blockers throughout pregnancy .