What are the effects on the fetus or baby if a pregnant or breastfeeding mother experiences anaphylaxis?

Effects of Maternal Anaphylaxis on the Fetus or Baby

Maternal anaphylaxis during pregnancy poses significant risks to both mother and fetus, primarily due to reduced placental perfusion from maternal hypotension, which can lead to fetal hypoxia and potentially fetal death if not promptly treated.

Pathophysiology and Risks to the Fetus

Anaphylaxis in pregnant women affects the fetus through several mechanisms:

• Reduced placental perfusion: Maternal hypotension during anaphylaxis decreases blood flow to the placenta, leading to fetal hypoxia 1
• Uterine vasoconstriction: Epinephrine (used to treat anaphylaxis) can cause uterine vasoconstriction, potentially worsening fetal blood supply 2
• Risk of fetal death: Persistent maternal hypotension can lead to fetal anoxia, spontaneous abortion, or perinatal mortality if not quickly reversed 1, 2

Management Considerations for Pregnant Women with Anaphylaxis

Despite concerns about epinephrine's effects on the fetus, prompt treatment remains essential:

• Positioning: Position the pregnant woman with left uterine displacement to avoid aortocaval compression 3
• Epinephrine administration: Administer epinephrine immediately as the first-line treatment, despite potential risks to the fetus, as the benefits far outweigh the risks 3, 2
• Fluid resuscitation: Administer crystalloid fluids rapidly (20 ml/kg) to restore maternal blood pressure 1, 3
• Emergency delivery consideration: If maternal hypotension persists despite resuscitation, emergent Cesarean section should be considered after 4 minutes of cardiac arrest, with delivery within 1 minute if resuscitation fails to achieve return of spontaneous circulation 1

Special Considerations for Breastfeeding

• It is unknown whether epinephrine is excreted in human milk 2
• Caution should be exercised when administering epinephrine to nursing mothers, but anaphylaxis treatment should never be withheld 2

Prevention and Long-term Management

For pregnant women with history of anaphylaxis:

• Pre-conception, pregnancy, and peripartum periods should be managed by a multidisciplinary team including high-risk obstetrics, anesthesia, and allergy specialists 1
• Avoidance of known triggers, prophylactic use of antihistamines, as-needed corticosteroids, and epinephrine on demand for anaphylaxis are standard approaches during pregnancy 1

Key Pitfalls to Avoid

1. Delaying epinephrine: The most dangerous error in anaphylaxis management is delaying epinephrine administration, which is especially critical in pregnancy 3

2. Improper positioning: Failing to position the pregnant woman with left uterine displacement can worsen aortocaval compression 3

3. Inadequate fluid resuscitation: Insufficient fluid administration may fail to restore maternal blood pressure and placental perfusion 1

4. Delayed consideration of emergency delivery: If maternal resuscitation fails to restore circulation within 4 minutes of cardiac arrest, perimortem Cesarean delivery should be performed within the next minute 1

In summary, while maternal anaphylaxis presents serious risks to the fetus through reduced placental perfusion and potential hypoxia, prompt and appropriate treatment of the mother with epinephrine, fluids, and proper positioning remains the best approach to protect both mother and baby.