Anaphylaxis During Pregnancy

Anaphylaxis is a severe allergic reaction, caused by the release of allergic chemicals such as histamine from allergic cells such as mast cells. Causes of anaphylaxis include foods, medications such as penicillin and NSAIDs, latex and insect stings, and bites. Symptoms of anaphylaxis can include urticaria and angioedema, difficulty breathing, nausea/vomiting, diarrhea, and low blood pressure that can in some case result in shock and death due to inability to circulate sufficient blood through the body..

Anaphylaxis can also occur during pregnancy, especially during labor and delivery, and can represent a special danger to the fetus, because low blood pressure related to anaphylaxis in the mother can affect blood flow to vital organs in the fetus, such as the brain and heart. Additional symptoms of anaphylaxis during pregnancy may include vaginal and vulvar itching, uterine cramps, and low back pain.

Pregnant woman in bed practicing prenatal yoga breathing
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Causes of Anaphylaxis During Pregnancy

The causes of anaphylaxis during most of the pregnancy are the same as in a non-pregnant woman. However, during labor and delivery, there are unique causes of anaphylaxis that need to be considered. In a past review of 23 patients with anaphylaxis during pregnancy, eight had anaphylaxis caused by penicillin and related antibiotics, six had anaphylaxis due to latex, one had anaphylaxis because of a bee sting, and the remainder had anaphlyactic reactions to other various medications.

Another study showed that there is a prevalence of 2.7 cases per 100,000 deliveries where antibiotics were the most common culprit. 

Penicillin and Related Antibiotics 

During labor and delivery, these medications represent the most common cause of anaphylaxis. Penicillin (and related antibiotics) is the drug of choice for the prevention of neonatal group B streptococcal (GBS) and other infections (such as prophylaxis during cesarean section) and is often given at the time of labor and delivery. Any person with suspected penicillin allergy should be further evaluated, particularly if there is an expected need for future penicillin (e.g. pregnant women who are colonized with GBS). Depending on a woman's prior history of reactions, penicillin allergy skin testing may be considered after discussing possible risks and benefits with an allergist. Alternately, a patient/medical care team may elect to avoid exposure to penicillin entirely during the pregnancy. In cases where there is not a good alternative to penicillin (e.g. syphilis during pregnancy), a penicillin desensitization can be performed under careful medical supervision, typically in an intensive care unit.

Latex Allergy

Latex allergy is also a common reason for anaphylaxis during labor and delivery.  Pregnant women with latex allergy should not be exposed to latex products during labor and delivery. For pregnant women with a possible latex allergy, consultation with an allergist prior to delivery is ideal. Testing for latex allergy in the United States is limited and, depending on the history, avoidance may be recommended despite results of any testing.

Treatment of Anaphylaxis During Pregnancy

The treatment for acute anaphylaxis during pregnancy is similar to that in non-pregnancy with a few additions. In particular, a pregnant woman should lie on her left side and when medical care is available, and maternal blood pressure and fetal heart rate should be monitored closely. The administration of epinephrine should not be delayed. Low blood pressure in the mother can lead to low blood flow to vital organs in the fetus, especially the brain. Anoxic brain injuries can occur when blood flow is reduced to the fetus for more than five minutes.

The best treatment for anaphylaxis during pregnancy is the prevention of anaphylaxis in the first place. Therefore, allergists are extremely important in the care of pregnant women who have a history of anaphylaxis to foods, medications, latex, and stinging insect allergy. Testing for most allergies should be deferred during pregnancy or performed using blood testing, in order to minimize the potential for anaphylaxis as a result of skin testing.

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