I sent the question off as Anne asked, and here was the reply from one of the docs who puts it all in perspective very, very well:
The procedures employed by those who recommend low dose aspirin is to start the drug after week 12-14, and thus any risk of miscarriage from the drug is extremely minimal, if at all. One should be aware, however, that the many physicians do not prescribe aspirin now because its ability to prevent preeclampsia is extremely low and if present in a yet to be defined Ã¢â‚¬Å“high riskÃ¢â‚¬Â group. Recall, it has taken a metaanlysis of over 30,000 patients to show a small statistical effect on outcomes. Thus, anyone contemplating its daily use must weigh the very small benefits to any small side effects the drug has.
One should also be aware of the pitfalls of the about to be released BMJ study. I am yet to see it, but it is claimed to be surveys of women about their nonsteroidal anti-inflammatory drug history before or in the early phase of a previous pregnancy, in a sense looking for retrospective information (looking back instead of prospectively, that is forward), Such studies can have many of what we call Ã¢â‚¬Å“confounding variables.Ã¢â‚¬Â For example women who take such drugs may be Ã¢â‚¬Å“less healthyÃ¢â‚¬Â than those who do not, and harbor illnesses that lead to miscarriage. For instance, if some of these women were taking their drugs for joint pains that later turned out to be lupus erythematosus, the latter and not the aspirin causing the miscarriage. This is not to say I would not heed the recommendations of such articles (intuitively, if possible one does not prescribe any drug in the first three months of pregnancy primarily to avoid any teratogenic potential they may have). I added this last paragraph to show how careful one must be when reading medicine by press stories, (and also because I arose early this morning and had some extra time at the computer.)
We've also posted this question and answer thread in the "Ask the Experts" section, too, under Aspirin and Miscarriage
Mom to Alicia (severe PE) 5/98 and Camille (htn, oligo) 4/03