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Management Strategies
Preconception Counseling/Contraceptive Methods
Ideally, a comprehensive cardiovascular examination should be undertaken before embarking on pregnancy. This includes a careful history and physical examination, an echocardiogram and an electrocardiogram. The additional prognostic benefit of cardiopulmonary exercise testing has not been defined, but may be helpful in some cases.
Preconception counseling in women with mechanical heart valves receiving anticoagulant treatment should include a discussion about the potential fetal and maternal risk associated with each of the possible anticoagulant regimes. The following issues should be understood by the mother: fetal risk associated with warfarin (congenital malformation and fetal loss rate) and maternal risk associated with heparin or LMWH, primarily thromboembolic events, and rarely thrombocytopenia or osteoporosis.
When counseling regarding anticoagulant options, consider the following factors associated with higher maternal thromboembolic risk: presence of mitral mechanical valve (highest risk in older style mechanical valve), prosthetic valve dysfunction (higher than normal baseline gradient across the valve), atrial fibrillation/flutter, previous thromboembolic event, left ventricular dysfunction, or elevated pulmonary pressure.
Women on warfarin should be warned that pregnancy tests have to be done as soon as a period is missed in order to avoid progression of pregnancy beyond 6 weeks while on and consequent fetal embryopathy. Switching of the warfarin to LMWH before pregnancy it is not recommended given the higher rate of thromboembolic events with LMWH.
Woman of childbearing age with tissue valves should be counseled about the lower pregnancy related risks; however, such a woman faces increased risk of redo surgery. Redo-surgery is almost inevitable. Mortality risk at the time of redo surgery varies among cardiac centers.
For women with congenital heart disease, transmission of congenital heart disease to offspring should be discussed. The risk of transmission is approximately 5-10% and varies with the maternal cardiac lesion.
A discussion about contraceptive methods is appropriate in all women with prosthetic heart valves. Combined (estrogen and progesterone) oral contraceptive pills can usually be used in women with tissue prostheses; however, caution is recommended in women with mechanical bileaflet valves or previous thromboembolism. In women with older types of mechanical valves (Starr Edwards and Bjork Shiley) estrogen-containing pills should be avoided, because of the higher thrombogenic risk (9). (see Contraception)
Medication use should be reviewed if a woman is contemplating pregnancy or is pregnant. The MOTHERISK website is an excellent resource.
Ante-partum Care
Coordinated care between a heart disease specialist, a hematologist, and a high-risk obstetrician at a high-risk pregnancy center should be implemented. The frequency of follow-up visits (clinical and echocardiographic) is dictated by the type of heart valve and the clinical status of the woman at time of conception. There is an expected increase in prosthetic valve gradients by the time of peak cardiac output (28-32 weeks gestation). However, significant or unusual changes in gradient or valve area may indicate valve thrombosis. If there is suspicion of mechanical valve thrombosis, a transesophageal echocardiogram should be performed.
Based on the available guidelines, (1,2) and our centre experience the following scheme of anticoagulation during pregnancy is proposed:
1. 1. Before the 6th week of gestation, switch warfarin to LMWH (2 times a day). Measure anti Xa level frequently to a target of 1.0 U/ ml. We recommend aspirin (81mg) in addition to LMWH.
2. 2. Strategies between the 13th and 36th weeks of gestation depend on the regime chosen:
a. Maintain the LMWH with careful follow-up; in patients with higher thromboembolic risk the anti Xa level may be targeted between 1 and 1.2 U/ml.
b. Switch back to warfarin; target an INR of approximately 3 (range 2.5- 3.5). In patients with lower thromboembolic risk (bileaflet aortic valve without atrial fibrillation or LV dysfunction) the INR range may be targeted between 2 and 3.
3. At 36 weeks gestation warfarin must be switched back to LMWH.
Women who develop mechanical valve thrombosis are at high risk for death. Changes in the anticoagulation regime, thrombolysis and cardiac surgery have all been used to treat women with valve thrombosis. The approach should be based on the individual case. Cardiac surgery carries a high risk for the fetus (10-11). There is limited data available regarding the use of thrombolytics in pregnancy, although successful cases of treatment of mechanical valve thrombosis with thrombolytics have been reported (12).
Fetal echocardiography can be offered to mothers with congenital heart disease. A fetal echocardiogram is done at approximately 20 weeks gestation.
Labour and Delivery
Labour and delivery should be planned carefully with a multidisciplinary team well in advance. It is important to communicate the delivery plan to the woman and to other physicians involved in her care. The best delivery plan is not useful if information is not readily available when needed.
A planned induction of labour is the safest option in pregnant women on anticoagulation.
Vaginal delivery is recommended in most instances. Good pain management for labour and delivery is very important in order to minimize maternal cardiac stress. To decrease maternal expulsive efforts during the second stage of labour, forceps or vacuum delivery is often utilized. To decrease potential harmful complications from difficult mid cavity-assisted delivery, uterine contractions are often utilized to facilitate the initial descent of the presenting part.
When women go into labour while still on warfarin or have only recently discontinued warfarin, cesarean delivery is necessary in order to avoid bleeding complications in the neonate, who will be secondarily anticoagulated.
The need for maternal monitoring is dictated by the functional status of women. In general, invasive monitoring is not required.
In general, endocarditis prophylaxis at the time of labour and delivery is not recommended. However, some experts continue to administer antibiotics because they feel that the risks of adverse reactions to antibiotics are small and the risk of developing endocarditis has major health consequences.
Post-partum Care
The hemodynamic changes of pregnancy may take up to six months to normalize. Women should be seen early after pregnancy (usually within 6-8 weeks). The frequency of additional follow up visits should be dictated by the clinical status of the women.
