Here's the most recent thing from the NICHD on LDA and conception: http://www.ncbi.nlm.nih.gov/pubmed?term ... on%20nichdClinical studies investigating the use of low-dose aspirin (LDA) as an adjuvant therapy to IVF have produced conflicting results. The conflicting results have come as a consequence of the heterogeneous mixture of clinical trials with lack of adequate power. Even after multiple meta-analyses, differing estimates of effect were calculated as to whether aspirin should be used in conjunction with IVF.
We know that women who are using IVF to conceive are likely to have implantation issues, so a clear benefit should show up here if there is a large effect. Since the data is equivocal, they're calling for a (expensive!) multi-center randomized controlled trial to see if there is a small benefit that's not obvious in the data we have.
The media is reporting (rather annoyingly and breathlessly) a bunch of conflicting meta-analyses here. When there are only small studies, and no big careful studies, there can be population bias. It can look like there's a benefit when really it was just an accident because the people enrolled in the population weren't going to get preeclampsia again anyway. Most women who get preeclampsia do not get it again regardless of what they do
to support later pregnancies. So it takes *very large* populations of women randomized to potential treatment or placebo to work out whether or not there's any benefit to any potential therapy. Since we don't have a lot of those studies, but we have a lot of small studies, they'll group together the data from 15 smaller studies and then slice and dice the data looking for any trends.
But I don't see the point of using a meta-analysis when we have actual big careful randomized controlled trials that show no benefit from aspirin. I think they are only finding little fluctuations in the data because they're doing a kind of math that we *know for sure* produces these sorts of effects. (The Expert thread on LDA talks about some of these known math problems.)
*However*, since there are no obvious problems with LDA, a lot of docs recommend it on the grounds that even if it's not doing anything, it can't harm, and maybe it is doing something and we just don't know. This makes me a little nervous; we know that other NSAIDs seem to increase miscarriage rates.