Women who are pregnant should approach using analgesics with caution. For example, though studies in humans have not conclusively shown that aspirin can cause birth defects, they have been found to cause birth defects in animal studies.

In humans there have been reports of low birth weight and possibly death in newborns whose mothers took large amounts of aspirin late in pregnancy. Women should not take aspirin during the last three months of pregnancy without a physician’s approval. Too much aspirin late in pregnancy has also been associated with:

• Bleeding problems in the fetus before or during delivery
• Increase in length of pregnancy
• Prolonged labor
• Severe bleeding in the mother before, during or after delivery

Opioids prolong labor. They have been shown to produce birth defects in animals, but this has not been confirmed in people. However, mothers who use too much of a narcotic during pregnancy risk creating a drug dependency in the fetus. The newborn baby may suffer withdrawal symptoms after the birth. Opioids can also cause breathing problems in the newborn if the mother takes the medication just prior to or during delivery.

Some opioids, such as certain codeines, have been shown to pass into breast milk.