Adverse Birth Outcomes More Likely in Babies Born from Influenza-infected Women

An assessment of data from babies born from pregnant women with and without 2009 H1N1 influenza infection during pregnancy has revealed fresh insights on the impact on the newborn. The findings highlight the need for increased efforts to avoid influenza infection during pregnancy.

The findings, published in the journal Birth Defects Research on January 9 showed that infants born to women with 2009 H1N1 influenza were more likely to be born preterm, than from women without 2009 H1N1.

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Babies born to women with this strain of influenza were also more likely to have a lower Apgar score at 5 minutes after birth.

The Apgar score is a point-based system designed to measure wellness in newborns one minute after birth, which takes into account their color, heart rate, reflexes, muscle tone, and respiration.

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The study was carried out as part of a collaboration between the CDC and multiple health departments in the USA, which were selected partly because of their demographic and regional diversity.

Lead researcher Dr. Kim Newsome, National Center on Birth Defects and Developmental Disabilities at the U.S. Centers for Disease Control and Prevention, commented on the implications of this study when speaking to UPI.com:

"The findings support the importance of pregnant women receiving the influenza vaccine, and of prompt treatment with antiviral medications for pregnant women suspected of having influenza."

The study sites comprised one third of the total number of cases of this strain of influenza in the United States for the study period, and included 490 women with maternal flu, 1446 controls (pregnant women without reported influenza) from the prior year, and 1451 controls from the same year. Control infants were matched for month of conception, sex, and county of residence.

When speaking to the same publication, Dr. Rahul Gupta commented on current rates of flu vaccination of women of childbearing age:

"The rate of flu vaccination of women of childbearing age, and especially those in the first trimester [of pregnancy], is unacceptably low… getting the flu vaccine early in pregnancy is one of the most important things you can do for yourself as an expecting mom.”

Comparison groups were limited to singletons (single-births). One limitation for this analysis was that while the model included maternal age and race/ethnicity, it did not include other potentially confounding maternal characteristics, such as comorbid conditions or maternal education.

This study supports prior evidence suggesting that severely ill women with this strain of influenza are more likely to have adverse birth outcomes than women without influenza. Furthermore, pregnant women infected with 2009 H1N1 influenza are more likely to become severely ill than nonpregnant women.

These findings highlight the importance of avoiding influenza in the first place – through vaccination – and in getting antiviral treatment as early as possible, in order to avoid severe illness during pregnancy.

The authors noted that further studies should focus on:

• whether outcomes differ depending on the stage of pregnancy at which women are infected with influenza
• comparisons of ICU admissions during pregnancy with and without influenza infection 

Reference:

Newsome, K., Alverson, C. J., Williams, J., Mcintyre, A. F., Fine, A. D., Wasserman, C., . . . Rasmussen, S. A. (2019). Outcomes of infants born to women with influenza A(H1N1)pdm09. Birth Defects Research. doi:10.1002/bdr2.1445