Aspirin (Low-Dose — Pre-eclampsia Prevention)

How it works

At low antiplatelet doses it irreversibly inhibits platelet cyclo-oxygenase, reducing thromboxane production and improving the prostacyclin-to-thromboxane balance that influences placental perfusion.

Prescribing in practice

• It should be started from the recommended point in the late first trimester in women meeting NICE risk criteria and continued until delivery, as benefit depends on early initiation in at-risk pregnancies.
• It is generally avoided where there is active peptic ulceration, significant bleeding risk or aspirin hypersensitivity.
• Low-dose use is considered appropriate in pregnancy for this indication, unlike analgesic-dose aspirin and other NSAIDs, which are avoided particularly in the third trimester.

Monitoring

Monitor blood pressure and for proteinuria and bleeding as part of routine antenatal surveillance rather than specific drug-level testing.

Counselling the patient

• Take the daily low dose as advised, ideally consistently, and continue until your midwife or obstetrician advises stopping.
• Report significant bruising, bleeding or stomach pain.
• This dose is used to lower the chance of pre-eclampsia and is different from painkiller doses of aspirin.

Evidence & guidelines

NICE recommends low-dose aspirin from the late first trimester for women at increased risk of pre-eclampsia, supported by meta-analyses showing reduced incidence.