Q:

10/10/2012
I wanted to enquire and see what current evidence is with dosing of IT around women who are receiving allergy shots and become pregnant. My current understanding is that if patients have not started shots and are pregnant to wait until after pregnancy. If on IT and still on buildup, hold current dose and resume buildup when pregnancy completed. If on IT and on maintenance dose to reduce dose by 50% for duration of pregnancy. Are these observations accurate and do we have specific evidence to support above.

A:
Thank you for your inquiry.

The best source to answer your question is the Allergen Immunotherapy parameter guidelines which are available to you at no charge online. You may access them through the Joint Council of Allergy, Asthma, and Immunology website or through the Journal of Allergy and Clinical Immunology. For your convenience, I have copied below the segment from the guidelines (Summary Statements) that deal most concisely with your question. As you can see, the following is suggested by the guidelines:

1. Immunotherapy is usually not initiated during pregnancy.
2. If pregnancy occurs during the “build-up” phase and the patient is receiving a dose unlikely to be therapeutic, discontinuation of immunotherapy should be considered.
3. Allergen immunotherapy maintenance doses can be continued at the same dose during pregnancy.
4. If the patient is in the “build-up” phase, the dose should be held as you mentioned above.

A discussion of the literature in more detail is contained within the reference itself.

Immunotherapy in pregnancy

Summary Statement 20a: Allergen immunotherapy can be continued but is usually not initiated in the pregnant patient.C

Summary Statement 20b: If pregnancy occurs during the build-up phase and the patient is receiving a dose unlikely to be therapeutic, discontinuation of immunotherapy should be considered.D

The physician must be aware of the benefits versus potential risks of immunotherapy in pregnant patients. Allergen immunotherapy is usually not initiated during pregnancy because of concerns about the potential adverse effects of systemic reactions and their resultant treatment on the fetus, mother, or both (eg, spontaneous abortion, premature labor, or fetal hypoxia).

If pregnancy occurs during the build-up phase and the patient is receiving a dose unlikely to be therapeutic, discontinuation of immunotherapy should be considered.

There have been no large prospective studies investigating the safety of immunotherapy in pregnancy. However, several retrospective studies suggest that there is no greater risk of prematurity, fetal abnormality, or other adverse pregnancy outcome in women who receive immunotherapy during pregnancy.

One retrospective study of the allergy clinic records of 109 pregnant patients who received immunotherapy and 60 pregnant patients who refused immunotherapy revealed a higher incidence of abortion, prematurity, and toxemia in the group that did not receive immunotherapy compared with the immunotherapy group.196

Another retrospective study of 121 pregnancies in atopic patients who had received immunotherapy during pregnancy found the incidence of prematurity, toxemia, abortion, neonatal death, and congenital malformation was no greater than that for the general population.195

The incidence of these adverse events was also similar to that seen in a group of 147 pregnancies in atopic patients who did receive immunotherapy, except for a greater incidence of abortion in the untreated group. Similar safety was demonstrated with VIT during pregnancies.197

In addition to improving the pregnant patient’s allergic condition, 2 studies suggest that allergen immunotherapy might prevent allergic sensitization in the child.198,199

One demonstrated an absence of allergen-specific IgE in paired cord blood, 199 and the
other demonstrated an inhibitory effect on immediate skin reactivity to grass allergens in some of the offspring.198

Both studies showed similar levels of allergen-specific IgG in paired cord blood and maternal blood samples.198,199

More research is needed to elucidate the effect of allergen immunotherapy during pregnancy on the subsequent development of allergen sensitization in the child.

Allergen immunotherapy maintenance doses can be continued during pregnancy. The initiation of immunotherapy might be considered during pregnancy when the clinical indication for immunotherapy is a high-risk medical condition, such as anaphylaxis caused by Hymenoptera hypersensitivity. When a patient receiving immunotherapy reports that she is pregnant, the dose of immunotherapy is usually not increased.

The recommended precautions for the prevention of adverse reactions are important in the pregnant patient because of the possible effect on the fetus, as well as the patient (see Table IV on reducing immunotherapy risk).

There is no evidence of an increased risk of prescribing or continuing allergen immunotherapy for a mother while breastfeeding and no risk for the breast-fed child.

Source: Cox L et al. J Allergy Clin Immunol Volume 127, Number 1.

Thank you again for your inquiry and we hope this response is helpful to you.

Sincerely,
Phil Lieberman, M.D.
AAAAI - American Academy of Allergy Asthma & Immunology