Respiratory Syncytial Virus Testing Uncommon in Pregnant Mothers

Testing for respiratory syncytial virus (RSV) infection during the influenza season is uncommon among pregnant mothers, and a slightly high proportion of tests that are performed often result in a misdiagnosis, according to a study in Clinical Infectious Diseases.

Additionally, the researchers found an association between RSV-positivity and pre-term delivery as well as a high rate of asthma in RSV women with pre-existing conditions.

“While we know RSV is a major cause of severe respiratory infections in young children, relatively less is known about RSV infection in adults,” study researcher Annette Regan, PhD, MPH, of Curtin University in Bentley, Western Australia, told Contagion^®. “We found that women were not commonly hospitalized with RSV during pregnancy; however, when they were, these infections could be severe, which may mean that strategies which can prevent these infections would have value.”

Researchers identified 1,604,206 pregnant women in Western Australia, California, Ontario, and Israel who were admitted to a total of 4 clinical sites for an acute respiratory infection or febrile illness. Pregnancy data were linked with laboratory testing and hospital discharge data. Patients were tested for RSV during the influenza seasons. The investigators obtained data on hospital admission, the results of the RSV tests, hospital length of stay, and birth outcomes.

In the study cohort, the incidence rate of hospitalizations related to an acute respiratory infection or febrile illness was 0.9% (n = 15,287). Among these patients, approximately 6% (n = 846) of pregnant women received a test for RSV. When tests used reverse transcription polymerase chain reaction, 2.5% (n = 21) of women were found to have a positive RSV diagnosis, with an observed incidence range of 1.9% in Ontario to 3.1% in Israel. Additionally, the positivity percentage ranged from 0% to 4.0% in 2011 to 2012 and 2013 to 2014, respectively. Only <1% of women who were tested for influenza received a positive diagnosis for both RSV and influenza.

A slight majority of testing and detections of RSV occurred later in pregnancy (63% and 67%, respectively), particularly in the third trimester. In the 38% of RSV-positive women with a pre-existing health condition, asthma was the most frequently reported condition (19%). Compared with RSV-negative women, a diagnosis of pneumonia was more frequent among RSV-positive women (19% vs 38%, respectively; P =.046), demonstrating that misdiagnosis may be common in these patients. In addition, the researchers also found a significant association between an RSV-positive diagnosis and pre-term birth compared with RSV-negative diagnoses (29% vs 15%, respectively; P =.034).

“This study helps us better understand severe RSV infection during pregnancy,” Dr. Regan explained. “An RSV vaccine is currently in advanced stages of clinical development, which is meant to be administered during pregnancy in order to protect infants in the first few months of life. Our results suggest that in addition to the benefits of vaccination to the infant, there may be some additional benefit to the mother.”

Considering this study was performed in mostly high-income countries, the researchers report hesitancy in attempting to generalize the findings to women in developing countries.

According to Dr. Regan, further studies are required to understand deeper implications of their findings. “We focused on hospitalized infection, but we should also better understand infections which may not require admission to hospital,” she added. Additionally, she suggested more research is necessary for elucidating “a better understanding of how these infections during pregnancy may impact the health of the baby.”