There are three clinical issues that arise while dealing wit11 pregnancy and prosthetic valve. The first one is the use of anticoagulants in pregnant women. Two groups of anticoagulants are available -warfarin and heparin. Both of them can cause significant risk in the mother and the fetus, whether hemorrhage or thrombo-embolic events. The second issue is the tolerability of hemodynamic load in pregnancy. Most of the patients with NYHA functional class I and I1 with adequate functiolling of prosthetic valve, tolerate the increased hemodynarnic overload of pregnancy.However, patients with higher functional class or severe cardiac dysfunction, pregnancy is a risk and needs to be avoided. The third issue is prosthetic valve replacement during pregnancy. It is better to treat before conception, but if it has to be done, it is better to delay till the fetus becomes viable, and caesarian section can be as a part of concomitant procedure.
Anticoagulation
Use of anticoagulation in pregnancy with mechanical prosthetic valve is mandatory.Heparin can cause osteoporosis and may not prevent valve thrombosis despite adequate dosage. Warfarin crosses placenta and can cause serious bleeding in the neonate if patient undergoes vaginal delivery. Warfatin can also cause embryopathy.Bioprosthetic valves are safer but may deteiiorate at an accelerated rate during pregnancy and hence repeat surgery may be needed during productive life span.
A) Warfarin (and coumarin group of drugs)
I)Fetal mortality and morbidity: Warfarin crosses the placenta and can cause spontaneous abortion, prematurity and still birth due to hemorrhage in the placenta or in the fetus. If continued through out pregnancy the incidence of spontaneous abortion varies from 4.29 to 50 per cent. Warfarin also causes embryopathy (fetal abnormalities) and central neivous system abnormalities.The incidence of warfarin embryopathy varies from <5 per cent to 67 per cent and the risk is dose related. The manifestations of warfatin embryopathy are telecanthus, hypoplnsia of nose, small nasal bones, depressed nasal bridge, hypoplastic alae nasi, choanal slenosis, punctuate dysplasia of the epiphysis of long boncs, cervical and lumbar ve tebral end plates.
Muteisid complicutior~s: Pregnancy is a hyper coagulable stale and the risk of thromboeinbolisrn is high but coumarin group e.g. warfarin can prevent these cpn~plications. While Salazar et a1 have reported no incidence of thrombo-embolism in their patients who were on coumarin derivatives, Born et a1 have reported 7.5 per cent incidence of mechanical valve thrombosis. It is recommended that when patients are on warfarin the (INR) inteimational normalized ratio of prothrombin time be maintained between 2 and 3 and a
low dose of aspirin is added.
B ) Heparin
1 ) Fetal complications:
Heparin does not cross the placenta and generally considered safe by some expcrts, There is no risk of embryopathy. However, spoiltaneous abortions have been reported similar to the use of coumarin group of drugs.Muteinrzl rorlzplication: ~ ~ ~ o l o n use g e d of heparin may cause complication like sterile abscesses, osteoporosis, risk of fractures, tlxombocytopenia and bleeding complications in the mother. The reported incidence of thrornbo-embolic complications varies from 12 per cent to 24 per cent. With heparin throughout pregnancy Shai+ounil have reported 24 per cent complications of valve thrombosis, 12 per cent embolic evcnts and 12 per ccnt major bleeding in their pregnant patients with mechanical prosthetic valves. Subcutaneous route of administration 01 heparin may not prevent thrombo-embolic phenomenon.Intravenous route using cannula has risk of bacterial endocxditis.
Low Molecular Weight Heparins (LMWH)
LMWH is an attractive alternative drug in pregnant women with prosthetic valves. It does not cross placenta. LMWH's have several advantages: low incidence of heparin induced thrombocytopenia and osteoporosis, superior absorption from subcutaneous injection site and bioavailability, 2 to 4 fold greater half life and hence more predictable and sustained anticoagulation. Limited data is available for its use in pregnancy with prosthetic lnechanical valves, however valve thromboses have been reported - most of them due to inadequate dosage.
Anticoagulation
Use of anticoagulation in pregnancy with mechanical prosthetic valve is mandatory.Heparin can cause osteoporosis and may not prevent valve thrombosis despite adequate dosage. Warfarin crosses placenta and can cause serious bleeding in the neonate if patient undergoes vaginal delivery. Warfatin can also cause embryopathy.Bioprosthetic valves are safer but may deteiiorate at an accelerated rate during pregnancy and hence repeat surgery may be needed during productive life span.
A) Warfarin (and coumarin group of drugs)
I)Fetal mortality and morbidity: Warfarin crosses the placenta and can cause spontaneous abortion, prematurity and still birth due to hemorrhage in the placenta or in the fetus. If continued through out pregnancy the incidence of spontaneous abortion varies from 4.29 to 50 per cent. Warfarin also causes embryopathy (fetal abnormalities) and central neivous system abnormalities.The incidence of warfarin embryopathy varies from <5 per cent to 67 per cent and the risk is dose related. The manifestations of warfatin embryopathy are telecanthus, hypoplnsia of nose, small nasal bones, depressed nasal bridge, hypoplastic alae nasi, choanal slenosis, punctuate dysplasia of the epiphysis of long boncs, cervical and lumbar ve tebral end plates.
Muteisid complicutior~s: Pregnancy is a hyper coagulable stale and the risk of thromboeinbolisrn is high but coumarin group e.g. warfarin can prevent these cpn~plications. While Salazar et a1 have reported no incidence of thrombo-embolism in their patients who were on coumarin derivatives, Born et a1 have reported 7.5 per cent incidence of mechanical valve thrombosis. It is recommended that when patients are on warfarin the (INR) inteimational normalized ratio of prothrombin time be maintained between 2 and 3 and a
low dose of aspirin is added.
B ) Heparin
1 ) Fetal complications:
Heparin does not cross the placenta and generally considered safe by some expcrts, There is no risk of embryopathy. However, spoiltaneous abortions have been reported similar to the use of coumarin group of drugs.Muteinrzl rorlzplication: ~ ~ ~ o l o n use g e d of heparin may cause complication like sterile abscesses, osteoporosis, risk of fractures, tlxombocytopenia and bleeding complications in the mother. The reported incidence of thrornbo-embolic complications varies from 12 per cent to 24 per cent. With heparin throughout pregnancy Shai+ounil have reported 24 per cent complications of valve thrombosis, 12 per cent embolic evcnts and 12 per ccnt major bleeding in their pregnant patients with mechanical prosthetic valves. Subcutaneous route of administration 01 heparin may not prevent thrombo-embolic phenomenon.Intravenous route using cannula has risk of bacterial endocxditis.
Low Molecular Weight Heparins (LMWH)
LMWH is an attractive alternative drug in pregnant women with prosthetic valves. It does not cross placenta. LMWH's have several advantages: low incidence of heparin induced thrombocytopenia and osteoporosis, superior absorption from subcutaneous injection site and bioavailability, 2 to 4 fold greater half life and hence more predictable and sustained anticoagulation. Limited data is available for its use in pregnancy with prosthetic lnechanical valves, however valve thromboses have been reported - most of them due to inadequate dosage.
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