Periconception Eosinophil Counts Predict Asthma Exacerbations in Pregnancy

Periconception eosinophil counts were independently associated with increased asthma exacerbation frequency during pregnancy, according to late-breaking findings presented at the 2026 American Thoracic Society (ATS) International Conference in Orlando, Florida. The findings suggest that a routinely available biomarker obtained at or near conception may help identify higher-risk patients earlier in gestation.

In an interview at ATS 2026, Christian Cardillo, MD, from Temple University Hospital, said asthma control during pregnancy remains highly variable, creating challenges for clinicians trying to anticipate which patients will deteriorate.

“We should all be aware that the physiologic changes during pregnancy in relation to asthma change from patient to patient, and it’s somewhat unpredictable,” Cardillo said.

Asthma exacerbations during pregnancy are associated with significant maternal and fetal risks, including acute respiratory failure, hospitalization, prolonged hospital stays, fetal growth restriction, and small for gestational age outcomes. Cardillo emphasized that identifying higher-risk patients earlier in pregnancy could help guide closer monitoring and coordination with subspecialists.

The late-breaking study included 31 pregnant patients with physician-diagnosed asthma treated at a single academic center. Investigators found that higher periconception absolute eosinophil counts were independently associated with increased exacerbation frequency during pregnancy.

Each 100 cells/µL increase in eosinophil count was associated with 0.20 additional exacerbations during pregnancy (adjusted β = 0.20; 95% CI, 0.12-0.28; P <.001) after adjusting for age, BMI, smoking status, controller therapy use, and prior exacerbation history. Cardillo noted that eosinophils are already part of routine clinical testing, making them a potentially scalable tool for risk assessment.

The analysis also suggested that greater eosinophil counts, particularly around 300 cells/µL, may better identify patients with type 2 inflammatory asthma phenotypes at higher risk for exacerbations during pregnancy. This threshold was consistent with prior retrospective data presented in 2025.

Cardillo said the findings remain exploratory but could eventually support earlier intervention strategies if validated in larger prospective studies. Future work will focus on more diverse cohorts and incorporation of objective pulmonary measures such as spirometry to strengthen risk prediction models.

“Most patients will obtain a CBC somewhere around 8 to 12 weeks,” he said. “While I don't think it's practice-changing at this very point in time, if we perform…more prospective studies…[it may become] a reflex cutoff where the patient will get hooked up with either [pulmonologists] or MFM [specialists] to have their asthma either taken a closer look at in terms of management or potentially get them started on new medications that can help them prevent exacerbations.”

Editor’s note: Relevant disclosures for Cardillo include AstraZeneca Pharmaceuticals and GlaxoSmithKline.

References

Cardillo C, Shenoy K, Karanam A, et al. (Poster Board # P1425) Periconception Eosinophil Count Is Independently Associated With Asthma Exacerbations During Pregnancy. Late-breaking poster presented at ATS 2026 in Orlando, Florida, on May 17.