Dear Sarah (KAB),

It really is hard to know which way to go isn't it?

I will try and answer your questions:

Your Dr is absolutely right in saying that aspirin and heparin work by blocking different parts of the clotting system. An easy way of thinking about it is that aspirin stops platelets from sticking to each other and the only way to reverse that is to make new platelets (takes 7 days), that is why anyone having an operation is asked to stop taking aspirin a week before.

Heparin on the other hand works against clotting factors in your blood, these are things that accentuate the formation of a clot and let it get out of control.

The big difference between aspirin and heparin is that heparin can 'dissolve' a clot whereas aspirin cannot. This is why if you still developed a clot despite being on aspirin, heparin would be added to dissolve and stabilise it.

Aspirin in making your blood less likely to form a clot because the platelets aren't as sticky to each other is the mainstay of treatment for anyone with clotting disorders, not just pregnant women. I would agree that taking aspirin alone will reduce your chance of miscarriage because of a clot to that of a normal woman. But as you yourself have said it does not remove the risk completely.

Taking both aspirin and heparin is like taking 2 drugs that do the same thing just by different mechanism with the additional benefit of disolving any clot that may form despite the aspirin.

I am sorry if this explanation is a bit repetitive or a bit simple, but it is just the way that I would think about it. Your doctor is probably also considering the issue of safety in pregnancy, not from the directly taking the drug but the potential risks of bleeding and that includes bleeding into the placenta...

Your obstetrician and haematologist will be the best people to talk to rather than your GP (no disrespect intended) mainly because they deal with these diseases more commonly than your GP and undoubtedly will be able to tell you about the kind of successes / complications they have seen with these treatments. Rest assured though that healthy pregnancies do happen and will happen for you too.

Let me know if this doesn't make sense.

Love
Gabby