(HealthDay News) -- You may take certain over-the-counter supplements and medications without thinking twice. But when you're pregnant, even drugs that you can buy without a prescription can affect the developing fetus.

The American Academy of Family Physicians offers these safety guidelines about medications and pregnancy:

• Don't take any medicine or herbal supplement without checking with your doctor.
• Try not to take any medicine during your first trimester of pregnancy, when your baby is most likely to be affected.
• If you are having pain, acetaminophen is usually safe for pregnant women to take for a short period. But you should first check with your doctor.
• Don't take aspirin while you're pregnant.
• Don't take an NSAID -- such as Advil, Motrin or Aleve -- while you're pregnant, particularly during your third trimester.