ASA use in patients at risk of preeclampsia

In a recent resident teaching clinic, I was surprised to hear a resident making a recommendation of a dose of ASA 81mg to a patient for prevention of pre-eclampsia. The resident had accurately identified a patient for whom low dose ASA would be indicated for this purpose, but the dose recommended was not consistent with the standard of care being practiced by obstetrical care providers at Mount Sinai Hospital, in Toronto. The resident and I discussed this recommendation and they indicated that their knowledge came from the Tools for Practice piece ASA use in patients at risk of preeclampsia by Desrochers et al. (2024). I indicated that I recommended ASA 162mg and we had some good teaching on the topic of preeclampsia prevention.

Later, I connected with other OB care providers across Canada and found that their standard of care was also a dose of ASA of 162mg. In my search, I was unable to find anyone who stated they used 81mg as their standard of care.

While I appreciate the thoroughness of this piece, it fails to highlight that the majority of OB care providers recommend a dose of ASA of 162mg to reduce the risk of pre-eclampsia consistent with the SOGC Guideline No 426 Hypertensive Disorders of Pregnancy: Diagnosis, Prediction, Prevention and Management (J Obstet Gynaecol Can 2022;44(5):547-71.e1) which the authors themselves reference. Specifically, this guideline states that care providers should "Consider using doses of acetylsalicylic acid higher than 81 mg/d in all women at increased risk of preeclampsia". This guideline also also states that it is recommended that ASA be taken at bedtime, another point the authors (and my resident) failed to mention.

By not acknowledging this key point of the Canadian guideline (which is highlighted in the Recommended Changes to Practice section on the second page of the publication), the authors have missed a key element of preeclampsia prevention and have failed to acknowledge the standard of care being practiced in Canada today. Similarly, our family physician learners who look to pieces such as this to provide succinct guidance, are somewhat misled. Future work ought to put more weight on Canadian and more up to date publications (the reference to the ACOG Guideline from 2018 is appropriate but relatively outdated and not as applicable as the Canadian Guideline published in 2022), as well as actual standards of practice, when making recommendations to Canadian Family Physicians.