In utero anaphylaxis.

Late fetal demise and hypoxic-ischemic neurologic injury after previously normal in utero development remain devastating outcomes of pregnancy, for which no cause is identified in many cases. Based on a case encountered, I propose that some of these incidents may be due to in utero anaphylaxis to food antigens that cross the placenta. Potential allergens to which pregnant women are exposed can be transported across the placenta, and the fetus is capable of producing IgE, the antibody responsible for anaphylaxis in humans. Whether this IgE is antigen specific is controversial with some studies indicating the ability to generate IgE to food antigens prenatally. Indirect evidence for in utero production of specific IgE is the high percentage of food reactions that occur on the first postnatal exposure to the food. I propose that some cases of stillbirth and prenatal hypoxic-ischemic injury may be due to in utero anaphylaxis.