Categories Spell Out Risks To Mom, Fetus

Q. How do I know what drugs are safe to take during pregnancy? - R.C., Portland, Maine

A. Fortunately, the FDA has classified the 10,000-plus prescription drugs into five pregnancy safety categories: Category A, B, C, D and X. If you read the warnings section of a package insert for any prescription medication, you’ll find the FDA category designation. You may not get that package insert if the medication you receive is placed in a pharmacy bottle, rather than in its original packaging.

The Physician’s Desk Reference, the reference text which all doctors and pharmacists use, always spells out any warnings for pregnant or nursing women.

And if you don’t receive a full description of the medication your doctor has prescribed, ask your pharmacist or doctor. Actually, it’s very important to let your doctor know that you’re pregnant or possibly pregnant before a prescription (or drug samples) is given to you.

The pregnancy categories are based upon increasing risk to a developing baby.

Category A means that studies have been done to show that there’s no risk of harm to the fetus in the first trimester (the most critical time in its development), and there’s no evidence of harm in later trimesters. The risk of harm in using a Category A drug is remote.

Category B’s explanation is a bit more complicated. It says that either (1) Studies in animals haven’t shown any risk in pregnancy, but there haven’t been controlled studies in pregnant women; or (2) Animals studies did show an adverse effect, but when these studies were repeated in pregnant women, the adverse effects were not seen.

Category C risk is less clear. It says that either (1) Studies in animals did indeed reveal adverse effects on the fetus, but there are no controlled studies in pregnant women to say whether the drug is safe or unsafe; or (2) Studies in women or animals are simply not available. Drugs in this category should be given only if the potential benefit justifies the risk to the fetus.

Category D states that there’s definite evidence of human fetal risk, but the benefits for pregnant women may be acceptable despite the risk, as in life-threatening diseases for which safer drugs cannot be used or are ineffective.

Category X states that studies in animals or humans have shown harm to a fetus, and that the risk of using the drug in pregnancy clearly outweighs any possible benefit.

Here are some examples of each:

Category A drugs: thyroid hormones and vitamin B6. There are very few drugs listed as Category A.

Category B drugs: Penicillin, Amoxicillin, Flagyl, Clindamycin, Zantac, and insulin.

Category C drugs: Vitamin C, aspirin (except in the third trimester, when it’s designated as Category D), Atenolol, Prilosec, Levaquin and Norvasc.

Category D drugs: Accupril (in the 2nd and 3rd trimesters); Tetracycline; Dilantin and Bactrim (in the 3rd trimester).

Category X drugs: Accutane.

Tylenol, by the way, has no formal rating.

The over-the-counter drugs make a general statement in the package insert that if you’re pregnant or nursing, ask your doctor before using the product. Your pharmacist can also be a great person to ask.

My general suggestion is that unless there’s a clear need for a medication, as in infection or high blood pressure, try to avoid subjecting your developing baby to any drugs. If you have cold symptoms or allergy symptoms, try to tough it out. Always try to choose the safest drug, but in the end, it’s up to you and your doctor to discuss the medical condition and weigh the risk to your baby against the benefit to you.