What are the implications of anaphylaxis in pregnancy?

From the Guidelines

Anaphylaxis in pregnancy should be treated immediately with intramuscular epinephrine (adrenaline) 0.3-0.5 mg (1:1000 concentration) injected into the mid-outer thigh, which can be repeated every 5-15 minutes if symptoms persist. This recommendation is based on the most recent and highest quality study available, which emphasizes the importance of prompt epinephrine administration in anaphylaxis management 1. The management principles for anaphylaxis in pregnancy are essentially the same as for non-pregnant patients, with epinephrine remaining the first-line treatment despite theoretical concerns about reducing uteroplacental blood flow.

Some key points to consider in the management of anaphylaxis in pregnancy include:

• Positioning the pregnant woman on her left side to prevent compression of the inferior vena cava by the gravid uterus, which could worsen hypotension
• Administering supplemental oxygen and intravenous fluids (crystalloids like normal saline at 1-2 L rapidly) after epinephrine administration
• Considering second-line medications such as antihistamines (diphenhydramine 25-50 mg IV) and corticosteroids (methylprednisolone 125 mg IV)
• Initiating continuous fetal monitoring if gestational age is viable, as fetal distress may occur due to maternal hypoxia and hypotension

It is also important to note that delaying epinephrine administration poses a greater risk to both mother and fetus than any potential side effects of the medication 2. After stabilization, identifying and documenting the trigger to prevent future reactions, and considering prescribing an epinephrine auto-injector for the patient to carry at all times during pregnancy are crucial steps in managing anaphylaxis in pregnancy. The signs and symptoms of anaphylaxis, including tachycardia, faintness, cutaneous flushing, urticaria, and a sensation of impending doom, should be recognized promptly to initiate timely treatment 3.

From the FDA Drug Label

Although epinephrine improves maternal hypotension associated with anaphylaxis, it may result in uterine vasoconstriction, decreased uterine blood flow, and fetal anoxia. The implications of anaphylaxis in pregnancy include fetal anoxia and decreased uterine blood flow due to uterine vasoconstriction caused by epinephrine administration.

• Key considerations: + Use epinephrine with caution during labor and delivery. + Potential risks to the fetus, including fetal anoxia, spontaneous abortion, or both. 4

From the Research

Implications of Anaphylaxis in Pregnancy

• Anaphylaxis in pregnancy is rare, but it can be associated with significant morbidity and mortality for the mother, fetus, and neonate 5.
• The prevalence of anaphylaxis occurring during pregnancy is approximately 3 cases per 100,000 deliveries 6, with a frequency estimated to be 1.5 to 3.8 per 100,000 pregnancies 7.
• The management of anaphylaxis occurring during the third trimester of pregnancy may be challenging due to the additive effects of aortocaval compression and cardiovascular disturbances of anaphylaxis 6.
• Anaphylaxis during pregnancy implies a risk to both mothers and newborns, with an estimated anaphylaxis-related maternal mortality rate of 0.05/100,000 live births 7.

Causes and Triggers of Anaphylaxis in Pregnancy

• Beta-lactam antibiotics, latex, and anesthetic agents are common causes of anaphylaxis during pregnancy 7.
• Other identified allergens include oxytocin, sodium and sucrose iron, laminaria, misoprostol, rubber from Foley catheter, oral phytomenadione, ranitidine, chamomile, and ant sting 8.
• Most cases of anaphylaxis occur during cesarean section, with 74.47% of cases reported peripartum 8.

Management and Treatment of Anaphylaxis in Pregnancy

• The recommended dosage and administration of adrenaline (epinephrine) for anaphylaxis is the same in pregnant and non-pregnant patients: 0.5 mg adrenaline intramuscularly in the mid-outer thigh (or dose of 0.01 mg/kg if <50 kg) 5.
• Prompt administration of epinephrine and emergency cesarean delivery in cases of severe reactions are suggested strategies for managing anaphylaxis during the third trimester of pregnancy 6.
• Collaboration among different specialists involved in the care of pregnant women is essential to support preventive strategies and reduce avoidable deaths 7.