NHS Choices Medical Reference
Aspirin may not be suitable to take if you have certain health conditions.
When to avoid aspirin
Low-dose aspirin should not be taken if you have:
Aspirin must not be given to anyone under 16 years old, unless under specialist advice.
Using aspirin with caution
Low-dose aspirin should be taken with caution if you have:
Occasionally, some people are advised to stop taking aspirin seven days before a planned operation. This should always be on the advice of your doctor or surgeon.
Pregnancy and breastfeeding
Low-dose aspirin (75mg) may be taken if you are pregnant or breastfeeding, but only on the recommendation of your GP. Aspirin at doses higher than 150mg per day is not recommended during pregnancy or breastfeeding.
Aspirin should be used with caution during the last three months of pregnancy because of the risk of haemorrhage (bleeding).