Allergies During Pregnancy

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Allergies During Pregnancy

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Allergies During Pregnancy
Allergies During Pregnancy
If you're allergic and pregnant, you might be wondering if your allergies or medications could harm your baby.
InteliHealth Medical Content

Reviewed by the Faculty of Harvard Medical School

If you're allergic and pregnant, you may have questions about whether your allergies or medications could harm your baby. Pregnancy can be a realistic worry for women with allergic asthma, since poor control of asthma during pregnancy is not healthy for the mother or baby. Pregnancy can reduce allergy symptoms in some women, and most — including asthma patients — have trouble-free pregnancies.

If your symptoms require medications, you may need to do some planning. Ideally, you should talk to the doctor treating your allergies or consult an allergist before becoming pregnant. Discuss the safety for pregnancy of each of the medications that you use. There's no way to predict how the immune system will react for an individual woman during her pregnancy. About one out of three women report their allergy symptoms (asthma or allergic rhinitis) get worse, another one out of three say they improve and the remainder notice no difference.

Most cases of allergic rhinitis (hay fever) are mild enough that they would not cause you to require any special planning for your pregnancy. Of course, it is not always realistic for you to determine the timing of your pregnancy. However, if you have severe hay fever, it would be ideal for you to plan your pregnancy so that your first trimester doesn't coincide with hay-fever season. Most allergy treatments are considered to be reasonably safe for use in pregnancy, but doctors have not organized studies large enough to prove absolute safety. For this reason, it is best to minimize the use of medicines during the first trimester, unless you and your doctor have determined that medicines are important for you to continue for your health. Try to avoid the triggers for your allergy symptoms during your pregnancy, so medication use can be minimized.

If you have been taking allergy shots before your pregnancy, you can continue them during pregnancy: current research suggests that they pose no harm to a fetus. However, most physicians would advise that you do not start allergy shots during your pregnancy to avoid any potential allergic reactions.

The US Food and Drug Administration rates every drug with a letter that identifies how safe a medicine appears to be in pregnancy. Ratings of category “A” indicate proven safety. Ratings of “A” are rare for medications, because a drug must be studied in large experimental trials to gain this rating. Most medicines are rated with a “B” or a “C” class rating. “B” ratings are provided when we have a reasonable amount of experience with a medication in pregnant women (even if no large trials have been conducted), and no reason to believe that the medicine would cause harm. If a medicine has not been used in pregnant women, or if it can be shown to cause any harms when it is used in pregnant animals, that medicine will get a class “C” rating or a worse rating. Your pharmacist or your doctor can help you to review the rating of any medication.

Controlling asthma during pregnancy is an important priority. Asthma inhalers range in their safety ratings, and most are assigned to Class B or Class C. Even if your inhaler has a rating of Class C, you should use it without restriction during pregnancy if your doctor advises you to do so. You should focus first on your asthma control, rather than your inhaler ratings. Several studies report that poor asthma control results in low birth-weight babies and preterm births. This may be related to the mother’s chemical or hormonal reaction to physical stress, or subtle shifts in oxygen and carbon dioxide gases within the bloodstream during an asthma flare. Asthma prevention by avoiding your triggers is especially important during pregnancy.

Some women need antihistamines to control allergy symptoms during pregnancy. Antihistamines block a major part of the body's chemical reaction to allergens, and they are among the most useful of allergy treatment medicines. Different brands may work equally well to prevent your allergy symptoms. However, they are not all equal with regard to pregnancy risk. Most of the antihistamines, including diphenhydramine (Benadryl), chlorpheniramine (Chlor-Trimeton), loratadine (Claritin), and cetirizine (Zyrtec), are classified as pregnancy risk category B by the U.S. Food and Drug Administration. This means that the risk of harm to a developing baby is very low based on the experience we have had so far with these medications in pregnant women, and evidence we have from animal studies. Another of the popular antihistamines, fexofenadine (Allegra), is best avoided if you are considering pregnancy, since it is a pregnancy risk category C drug. There is not enough evidence collected from studies in humans to determine the safety of this drug in pregnancy, and in one animal study a very high dose of fexofenadine was linked to reduced birth weights.

If antihistamines do not control your allergy symptoms, there are other drugs that can be used, but most of them are risk category C. These include decongestants like phenylephrine (Sudafed PE) or pseudoephedrine tablets (Sudafed), and phenylephrine and oxymetazoline nasal sprays (Neo-Synephrine and Afrin). Corticosteroid nasal sprays like fluticasone (Flonase) and beclomethasone (Vancenase) also are rated as category C. Cromolyn sodium nasal spray (Nasalcrom) is one of the few allergy drugs (besides many antihistamines) classified as risk category B.


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Last updated January 12, 2012

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