The allergy season is in full swing in a significant portion of the United States. As tree pollen falls in a thin layer of yellow green on parked cars and some of us cling to our masks despite full vaccination, we turn our attention to a 2020 study that found a very high prevalence of allergies among infertility patients and evaluated the potential impact of allergies on successful pregnancies.

Study Questions

How common are allergies in men and women receiving infertility treatments? Are allergies associated with better or worse IVF outcomes?

Key Findings

• Among the 493 couples in the study, 54% of female partners had at least one allergy, with 27% of male partners reporting at least one allergy.
• Interestingly, 76% of women with PCOS reported having at least one allergy.
• The prevalence of allergies, especially among women, was much higher than the reported prevalence in the general population (10-30% in the US).
• Couples with allergies were had higher number of treatment cycles, suggesting less success per cycle, while the number of embryos transferred per cycle was paradoxically higher.
• Women with allergy were statistically more likely to have a negative hCG (pregnancy) test after each treatment cycle. In one age group (35-37), women with allergies were approximately 25% less likely to have a successful IVF cycle than those without, but this effect was not observed in other age groups.

Allergy, Immune System and Reproduction 

For an establishment and maintenance of an early pregnancy – aside from the endometrial decidualization that prepares the endometrium for the embryo’s nutritional and structural needs – the  maternal immune system has to undergo a complex process of reprogramming. Genetically speaking, the implanting embryo is 50% of paternal origin, which makes it a foreign “invader” in the eye of the mother’s immune system. This In order for the maternal body to accept and nurture the embryo, regulatory T cells protect the embryo from rejection. Other immunomodulating agents like cytokines, macrophages, dendritic cells and natural killer (NK) cells are involved in this process – and a malfunction or an imbalance of one part of the process can lead to implantation failures and early pregnancy loss.

On the male side, less is known about immunological mechanisms involved in reproduction. However, some studies found that inflammation from hyperactive immune system can lead to the destruction and abnormalities in sperm, as well as obstructions in the passage for the sperm from the testes.

Allergies are caused by dysfunctions of the many of the same immune cells and processes involved in these fertility processes – and this has some scientists looking into the possible connection between allergies and fertility. Some studies investigated whether allergies are associated with gynecological conditions with fertility implications, such as endometriosis and ovulatory dysfunction. Results are mixed.

What This Means for You & Your Fertility

The extremely high prevalence of allergies among fertility patients, compared to the general population is fascinating, and inflammation, also involved in allergic reactions, has already been associated with poor outcomes in IVF. However, at the moment, evidence is still too sparse and mixed to say whether allergies and fertility issues are connected, and what exact mechanisms and pathways may connect the two. Immunological processes in general and immunology of reproduction in specific are two rapidly evolving areas of biomedical research, so we may see more studies confirming the associations or elucidating the mechanisms, which can lead to more actionable insights in the near future.

For the time being, if you are struggling with getting pregnant or early-stage pregnancy loss and have severe allergies, it may be a good idea to consult a physician with expertise in reproductive immunology. For example, the Center for Human Reproduction in New York City recommends women with severe allergies to suspect immunological causes.

Some lifestyle changes to address systemic inflammation may also help.

As always, please reach out if you have any questions (or need a tissue). We are with you.

Study Vitals

• Title: High prevalence of allergy in patients undergoing in vitro fertilization and embryo transfer
• Authors: Negar Esfandiari, Carleigh Nesbit, Julia Litzky, et al.
• Publication date: February 2020
• Journal: Journal of Assisted Reproduction and Genetics
• Study type: Retrospective cohort study.