Aspirin is not the preferred fever-reducing medication to take while pregnant, because there are safer and equally effective alternatives. Yet don’t worry if you have unknowingly taken a couple of aspirin on a couple of occasions. This is unlikely to harm your baby. The main concern with aspirin is that prolonged high doses, especially in the third trimester, may cause bleeding in mother or baby (aspirin is an anticoagulant) or interfere with the normal onset of labor (aspirin inhibits prostaglandin’s). Obstetricians sometimes use low-dose aspirin to prevent pregnancy-induced hypertension, eclampsia, and other intrauterine problems.
Ibuprofen (Motrin, Nuprin, and Advil) is safer than aspirin during pregnancy, but take it only with a doctor’s advice. It seems to be safe to take in the first two trimesters because there have been no studies linking ibuprofen with congenital defects. Ibuprofen does not have the anticoagulant effect of aspirin, and is therefore unlikely to cause bleeding in mother or baby when taken in the third trimester. Because it inhibits prostaglandins (natural hormones that influence labor), it must be used with caution during the third trimester. Ibuprofen can also interfere with the normal blood flow within the heart and blood vessels of the baby during the third trimester. These effects are likely to disappear when the drug is stopped and have not been shown to harm baby.
Acetaminophen is safe to take throughout all stages of pregnancy. It is an effective fever-reducer and an analgesic for pain. Studies have shown that high doses of acetaminophen taken throughout pregnancy may be harmful to mother and baby. Acetaminophen, if used in the proper dosage and for the usual 2-3 day illnesses associated with fever, is safe for mother and baby.