Wednesday, January 09, 2019

Study: Outcomes Of Infants Born To Women With Influenza A(H1N1)pdm09

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Photo Credit – CDC


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Researchers have long known that during the 1918 pandemic an extraordinarily  high number of pregnant women died from the influenza, and those that survived endured a very high miscarriage rate. Again - during the much milder 1957 Asian Flu - pregnant women reportedly suffered disproportionately higher mortality rates than non-pregnant women of the same age.

In a Perspective, written by 3 CDC physicians (Sonja A. Rasmussen,  Denise J. Jamieson, Joseph S. Bresee) and published in a 2008 CDC EID Journal  article - Pandemic Influenza and Pregnant Women - we get this assessment of the historic impact of influenza on pregnant women.
Although appropriate nonpregnant control groups were generally not available, mortality rates among pregnant women in the pandemics of 1918 and 1957 appeared to be abnormally high (5,7). Among 1,350 reported cases of influenza among pregnant women during the pandemic of 1918, the proportion of deaths was reported to be 27% (5).

Similarly, among a small case series of 86 pregnant women hospitalized in Chicago for influenza in 1918, 45% died (6). Among pregnancy-associated deaths in Minnesota during the 1957 pandemic, influenza was the leading cause of death, accounting for nearly 20% of deaths associated with pregnancy during the pandemic period; half of women of reproductive age who died were pregnant
More than a year later - during the 2009 H1N1 pandemic - we were reminded of the heavy toll that influenza infection can have on pregnant women, and their offspring. 
  • In the fall of 2009 we learned that pregnant women were six times more likely to be hospitalized than non-pregnant women (see Pregnancy & Flu: A Bad Combination).
  • And in 2011, in BMJ: Perinatal Outcomes After Maternal 2009/H1N1 Infection we saw a study where pregnant women who were admitted to the hospital with an  H1N1 infection experienced a 3 to 4 times higher rate of preterm birth, 4 to 5 times greater risk of stillbirth, and a 4 to 6 times higher rate of neonatal death
Since then, we've looked at literally dozens of studies that have attempted to quantify the impact of influenza infection on both pregnant women and their offspring. While some of these studies are more compelling than others, we've seen a wide spectrum of sequelae linked to maternal flu infection, including:
Of Pregnancy, Flu & Autism
Pregnancy, Influenza & Elevated Psychosis Risks In Adult Offspring
UK: Pregnancy And Swine Flu
BMJ Study: Pregnancy & Flu
At the same time we've seen multiple studies confirming the benefits of flu vaccination and the early use of antivirals in protecting the lives of pregnant women and their unborn child, including:
Pediatrics: Maternal Flu Vaccination Extends Protection To Infants
Clinical Infectious Diseases: Flu Vaccine May Reduce Incidence of Stillbirth

JID: Benefits Of Early Use of Influenza Antivirals In Pregnancy

Despite ample evidence of harm to expectant mothers and their offspring from influenza infection - and studies that show the benefits of influenza vaccination to this vulnerable cohort - uptake of the flu vaccine among pregnant women is less than doctors would like to see.

Some of this reluctance is due to the persistent anti-vaccine rhetoric on the internet and in the media - including unfounded claims that the 2009 H1N1 vaccine was responsible for `thousands’ of miscarriages. The science, however, overwhelmingly supports the safety of flu shots for pregnant women.
While it doesn't appear to break any new ground (alas, the full study is behind a pay wall), we've a new study - published today in Birth Defects Research - which finds once again that maternal influenza infection can exact a heavy toll on both the mother and unborn child.


RESEARCH ARTICLE

Outcomes of infants born to women with influenza A(H1N1)pdm09

Kim Newsome, C. J. Alverson, Jennifer Williams, Anne F. McIntyre, Anne D. Fine, Cathy Wasserman, Kathryn H. Lofy, Meileen Acosta, Janice K. Louie… See all authors

First published: 09 January 2019
https://doi.org/10.1002/bdr2.1445
Abstract Background

Pregnant women with influenza are more likely to have complications, but information on infant outcomes is limited.
Methods

Five state/local health departments collected data on outcomes of infants born to pregnant women with 2009 H1N1 influenza reported to the Centers for Disease Control and Prevention from April to December 2009. Collaborating sites linked information on pregnant women with confirmed 2009 H1N1 influenza, many who were severely ill, to their infants' birth certificates. Collaborators also collected birth certificate data from two comparison groups that were matched with H1N1‐affected pregnancies on month of conception, sex, and county of residence.

Results


490 pregnant women with influenza, 1,451 women without reported influenza with pregnancies in the same year, and 1,446 pregnant women without reported influenza with prior year pregnancies were included. Women with 2009 H1N1 influenza admitted to an intensive care unit (ICU; n = 64) were more likely to deliver preterm infants (< 37 weeks), low birth weight infants, and infants with Apgar scores <= 6 at 5 min than women in comparison groups (adjusted relative risk, aRR = 3.9 [2.7, 5.6], aRR = 4.6 [2.9, 7.5], and aRR = 8.7 [3.6, 21.2], for same year comparisons, respectively). Women with influenza who were not hospitalized and hospitalized women not admitted to the ICU did not have significantly elevated risks for adverse infant outcomes.
Conclusions

Severely ill women with 2009 H1N1 influenza during pregnancy were more likely to have adverse birth outcomes than women without influenza, providing more support for influenza vaccination during pregnancy.
        (Continue . . . )

Newborns face risks when born to women with the flu

Wiley

Pregnant women with influenza are more likely to experience complications, but how this affects infants is unclear. A new Birth Defects Research study uncovers the potential risks to infants.

The study included 490 pregnant women with influenza, 1451 women without influenza with pregnancies in the same year, and 1446 pregnant women without influenza with prior year pregnancies. Women with 2009 H1N1 influenza admitted to an intensive care unit were more likely to deliver preterm infants, low birth weight infants, and infants with low Apgar scores than women in the other groups.

Women with influenza who were not hospitalized, as well as hospitalized women not admitted to the intensive care unit, did not have significantly elevated risks for adverse infant outcomes.

"The message of this work is particularly timely in the midst of the current influenza season. Our study found that severely ill women with 2009 H1N1 influenza during pregnancy were more likely to have adverse birth outcomes--such as their baby being born preterm or of low birth weight--than women without influenza," said senior author Dr. Sonja Rasmussen, of the University of Florida. "These 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."
 

While the focus of influenza during pregnancy studies over the past decade have been primarily on the impact of maternal H1N1 infection, the 1957 H2N2 pandemic produced similar results, and so it can be assumed that other influenza subtypes may be able to produce similar - or possibly even worse - outcomes.


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