There's an older thread here:
Pregnancy on mechanical valve. There are also others - search for 'pregnancy' or 'pregnant.'
I had two pregnancies on an On-x mechanical aortic valve. Both went very well. I saw three different specialists who presented four different options: warfarin the entire pregnancy; low molecular weight heparin injections from discovering the pregnancy until week 13, then warfarin until delivery; low molecular weight heparin injections the entire pregnancy. With all of these three, one would switch to drip heparin for delivery. These three options are in order of least to most risk for the mom, but they're in order of most risk to least for the baby. In other words, what's less risky for mom is more risky for the baby. The fourth option was plavix and aspirin the entire pregnancy - which was newer at the time but my cardiothoracic surgeon had three women and four pregnancies do well on it.
I am very risk averse and wanted to provide the least risk for the baby, so I went with taking low molecular weight heparin injections for the entirety of both pregnancies. This is in part due to the fact that I take a fairly high dose of warfarin (12.5-15 mg daily) - the doctors said that published case histories at the time showed that under 5mg a day was relatively likely to not cause any problems for the baby, but at my dose chances of harm to the baby were higher. Birth defects occur due to warfarin use during the first 13 weeks. After that there's less of a risk of birth defects, but warfarin crosses the placenta and could cause a brain or other bleed for the baby. Low molecular weight heparin doesn't cross the placenta.
I went to the high risk maternal fetal medicine doctors a lot and was monitored very closely - which means I got a lot of baby pictures from all the ultrasounds. I had weekly blood tests to monitor how anticoagulated my blood was, and frequent adjustments to the heparin. I saw the cardiologist every trimester. I did not have a C-section with either child, as the risk of bleeding from surgery is higher than for a non-cesarean birth. Low molecular weight heparin injections twice a day aren't easy - they're painful and the places you inject get horribly bruised and purple. And doctors like to avoid an epidural for women on heparin, as there have been cases of paralysis reported (due to clotting at the spine I guess - though it is rare I believe). I did have to be induced for both my children and after 36 hours of labor with the first one one I got an epidural despite the risks. I also got an epidural with the second for medical reasons (what we were trying to avoid by having the epidural was more likely than a blood clot from an epidural). I made it through both of those fine with no paralysis.
I would not change a thing. I had two healthy children and no issues related to my heart or anticoagulation. I had nine months where I ate all the salads and spinach I wanted (no vitamin k issues). I still send holiday cards of my children to the nurses at the high risk pregnancy medical practice. I won't have a third child because it's too risky and my family feels complete.
I was very fortunate, to be sure, but I don't think that good fortunate is all that unusual anymore. You should definitely talk to your doctor, or better yet more than one. It's more work and risk than for a woman who doesn't have a mechanical heart valve, but pregnancy is already pretty hard. It's very different if you have a mechanical mitral valve rather than or in addition to a mechanical aortic valve, as the risks are higher.
I hope this is helpful.
