Medication during pregnancy

I'm trying to get pregnant. What do I need to know about medications?

You’re wise to be concerned about the impact medications can have on your pregnancy. The good news is that many drugs are safe for a pregnant woman and her baby. Many women believe that all medications pose a risk to the fetus. However, this isn’t the case. You have about a three per cent chance of having a baby with a severe congenital malformation (that is, the baby is born without a particular organ, or an organ that doesn’t work properly or looks abnormal). Drugs are responsible for less than one per cent of these congenital malformations. (In 65 to 75 per cent of all cases, the cause is unknown. Fifteen to 25 per cent are due to genetics and three per cent are due to the mother having an infection such as rubella or herpes while pregnant.)

It can sometimes be difficult to determine whether a medication is safe during pregnancy because pregnant women generally do not volunteer for studies that test out new drugs. However, certain drugs, such as some headache, cough and allergy medications, have been used by women throughout their pregnancies with no ill effects, and are known to be safe. The rule of thumb is to take the lowest effective dose.

Always talk to your pharmacist or physician before using any of these over-the-counter medications. It is important that you know how much you should take and how far into your pregnancy you can safely use these drugs.

Headaches, pain or fever
Use acetaminophen (e.g. Tylenol). ASA (e.g. Aspirin), ibuprofen (e.g. Advil and Motrin) and naproxen (called Na-prosyn) should not be used during the last trimester because they can prolong labour and increase bleeding in both the mother and fetus.

Nausea or heartburn
For heartburn, try calcium carbonate (e.g. Tums). For severe nausea and vomiting, your doctor may prescribe doxylamine-pyridoxine (e.g. Diclectin).

Stuffed-up nose
Try taking pseudoephedrine oral tablets (e.g. Sudafed). Be careful of combination cold products that also contain acetaminophen to treat a fever, because if you are already taking acetaminophen you will end up with a double dose.

Seasonal allergies
To relieve sneezing and itchy eyes, try chlorpheniramine (e.g. Chlor-Tripolon) or diphenhydramine (e.g. Benadryl). The downside is that these medications may make you sleepy.

Yeast infection
Try miconazole (e.g. Monistat) or clotrimazole (e.g. Canesten). If you’ve never had a yeast infection before, talk to your doctor.

Women with medical conditions such as diabetes, depression and clotting disorders can continue to take certain medications to treat these conditions while they are pregnant. Your physician may recommend that you change your medication to a drug with a well-established safety record. Or she may take you off your medication, such as fluoxetine for depression, prior to delivery because it may cause complications. You and your doctor should discuss what treatment is best and safest for you.

Some medications fall into the category of teratogens, which means they pose a potential risk to the fetus and should be avoided during pregnancy. There are approximately 30 known teratogenic medications. Examples include the acne medication isotretinoin (e.g. Accutane), the blood thinner warfarin (e.g. Coumadin) and the antibiotic tetracycline. Very high doses of vitamin A (more than 10,000 IU per day) can also be teratogenic.

For detailed information on the safety of medications during your pregnancy, visit or call 416-813-6780 (no 1-800 number is currently available).

Colleen Brady is a practising pharmacist in Vancouver and lecturer in the faculty of pharmaceutical sciences at the University of British Columbia.

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