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ECDC Health Content: Pandemic influenza A(H1N1) 2009 in pregnancy places women at higher risk of adverse outcome - published analytic study from the United States (August 5, 2009, edited)
Scientific Advances - Pandemic influenza A(H1N1) 2009
Pandemic influenza A(H1N1) 2009 in pregnancy places women at higher risk of adverse outcome - published analytic study from the United States
Jamieson D, Honein M, Rasmussen S, Williams J, Swerdlow D, Biggerstaff M, et al. H1N1 2009 influenza virus infection during pregnancy in the USA. Lancet 2009; July 29, 2009 DOI:10.1016/S0140-6736(09)61304-0, http://www.thelancet.com/journals/la...304-0/abstract
Description:
Earlier this year the US Centers for Disease Control and Prevention (CDC) reported cases of influenza A(H1N1)v virus infection among pregnant women in the US. A number of these infections resulted in complications or even death.[1,2] Working with American state authorities and clinicians, CDC undertook an analytic study of the first month of transmission in the USA (15 April ? 18 May) which has now been published.[3] It is based on 34 cases, eleven of whom were hospitalised. The article also documents that over the longer two-month period (between 15 April and 16 June) six deaths in infected pregnant women were reported in the US out of a total of 45 deaths in all known A(H1N1)v-infected people. All of the deaths were in relatively healthy pregnant women who developed primary viral pneumonia and subsequent acute respiratory distress syndrome.[3] The analytic study compared the experience of three groups of infected people: the 34 pregnant women, non-pregnant women of reproductive age (15?44 years old), and the general population. The estimated rate of admission for influenza A(H1N1)v virus infection in pregnant women during the first month of the outbreak (0.32 per 100 000 pregnant women, 95% CI 0.13?0.52) was higher both than for non-pregnant infected women (0.04 cases per 100 000: 95% CI 0.03?0.06) and for the general population(0.076 per 100 000: 95% CI 0.07?0.09). The number of pregnant women in the population had to be estimated.[3] Hence an infected pregnant woman was four to five times more likely to be admitted to hospital than a non-pregnant woman (RR 4.3, 95% CI 2.3?7.8). Women in all three trimesters of pregnancy were in the series. The commonest reported underlying condition for the 34 women was a history of asthma (seven women). However, only one woman was regularly taking medication for asthma and generally chronic underlying conditions were under-represented (if pregnancy itself is excluded) compared with other persons hospitalised or dying in association with influenza A(H1N1)v.[3] The signs and symptoms reported for the pregnant women were no different from those reported for infected non-pregnant women or all others infected, except that they more often included shortness of breath. Three case examples from the hospital series, including one death, were published earlier see Box, below.[1]
ECDC Comment (4 August 2009)
This analytic study found that pregnant women were at higher risk for influenza-associated complications compared with women who are not pregnant and this risk may be even higher for pregnant women with underlying medical conditions such as asthma. This has been previously observed with seasonal influenza and during the 1918 and 1957 pandemics.[4?7]
Previous studies of seasonal influenza and pregnancy have found that the risk of severe disease increased as pregnancy progressed from the first to the third trimester.[4,5] No difference in experience could be detected for the trimester of pregnancy in this study but the numbers were really too small at this stage to detect such differences. One of the studies found the presence of underlying medical conditions increases the risk of hospitalisation but that has not been the obvious experience with A(H1N1)v influenza.[3,4] This increased risk of complications is thought to be related to several physiological changes that occur during pregnancy, including alterations in the cardiovascular, respiratory and immune systems.
The impact of the pandemic on the pregnancy itself, the unborn child and the newborn, remains to be described, though during the 1918 and 1957 pandemics there were reports of increased risk of miscarriage, premature delivery and other adverse outcomes.[6?8]
These findings indicate that pregnant women deserve particular care during a pandemic and some countries have already issued guidance for maternity services and clinicians.[3,9,10,11] The consistent finding of primary viral pneumonia and its association with a poor outcome is disturbing.
Although little is known about the safety or effectiveness of the use of antivirals during pregnancy, any potential risk for the foetus or pregnant woman is likely to be outweighed by the expected benefits of its use in a pandemic. Consequently, the antivirals that are effective against A(H1N1)v virus, oseltamivir and zanamivir, have recently been licensed for such use by the European Medicines Agency (EMEA).).[12] The UK and the CDC interim guidance for clinicians recommend that pregnant women with confirmed, probable or suspected infection with influenza A(H1N1)v virus should receive antiviral treatment. The drug regimen should be initiated, if possible, within 48 hours of the onset of symptoms. In addition, the American guidance suggests that pregnant women in close contact with a person with confirmed, probable or suspected infection with influenza A(H1N1)v virus should receive a 10-day course of chemoprophylaxis with oseltamivir or zanamivir. By contrast, the authors of the UK guidance do not feel this is necessary.[10,11]
The American guidance suggests that in clinical settings, including settings that provide care for pregnant women, patients should be screened for signs and symptoms of febrile respiratory illness at the initial point of contact, and promptly segregated and assessed. Because of the increased risk for severe complications, the public health response to outbreaks of influenza A(H1N1)v infection should include considerations specific to pregnant women.[3,9?11]
Box: Case examples[1]
Patient A. A 33-year old woman at 35 weeks? gestation had a one-day history of myalgia, dry cough and low-grade fever. Four days later her symptoms worsened and severe respiratory distress developed. That same day she was put on mechanical ventilation and a caesarean delivery was performed. The baby was healthy and was discharged home but the mother developed acute respiratory distress syndrome (ARDS) and died, despite receiving oseltamivir and antibiotics. A specimen from the woman was confirmed positive for influenza A(H1N1)v.
Patient B. A 35-year old woman at 32 weeks? gestation had a one-day history of shortness of breath, fever, cough, diarrhoea, headache, myalgia, sore throat and inspiratory chest pain. A rapid influenza test was negative and she received a parenteral nonsteroidal anti-inflammatory medication, acetaminophen, and inhaled albuterol and was discharged home. The next day she was seen by her obstetrician and a specimen was taken and infection with influenza A(H1N1)v virus was confirmed. After receiving additional treatment (not including oseltamivir) she recovered fully and her pregnancy proceeded normally.
Patient C. A 29-year old woman at 23 weeks? gestation had a one-day history of cough, sore throat, chills, subjective fever and weakness. One of her sons, aged 10 years, had similar symptoms a week before the mother and another son, aged seven years, had become ill on the same day as the mother. A specimen from the mother was confirmed positive for A(H1N1)v. After being prescribed oseltamivir her pregnancy proceeded normally.
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Scientific Advances - Pandemic influenza A(H1N1) 2009
Pandemic influenza A(H1N1) 2009 in pregnancy places women at higher risk of adverse outcome - published analytic study from the United States
Jamieson D, Honein M, Rasmussen S, Williams J, Swerdlow D, Biggerstaff M, et al. H1N1 2009 influenza virus infection during pregnancy in the USA. Lancet 2009; July 29, 2009 DOI:10.1016/S0140-6736(09)61304-0, http://www.thelancet.com/journals/la...304-0/abstract
Description:
Earlier this year the US Centers for Disease Control and Prevention (CDC) reported cases of influenza A(H1N1)v virus infection among pregnant women in the US. A number of these infections resulted in complications or even death.[1,2] Working with American state authorities and clinicians, CDC undertook an analytic study of the first month of transmission in the USA (15 April ? 18 May) which has now been published.[3] It is based on 34 cases, eleven of whom were hospitalised. The article also documents that over the longer two-month period (between 15 April and 16 June) six deaths in infected pregnant women were reported in the US out of a total of 45 deaths in all known A(H1N1)v-infected people. All of the deaths were in relatively healthy pregnant women who developed primary viral pneumonia and subsequent acute respiratory distress syndrome.[3] The analytic study compared the experience of three groups of infected people: the 34 pregnant women, non-pregnant women of reproductive age (15?44 years old), and the general population. The estimated rate of admission for influenza A(H1N1)v virus infection in pregnant women during the first month of the outbreak (0.32 per 100 000 pregnant women, 95% CI 0.13?0.52) was higher both than for non-pregnant infected women (0.04 cases per 100 000: 95% CI 0.03?0.06) and for the general population(0.076 per 100 000: 95% CI 0.07?0.09). The number of pregnant women in the population had to be estimated.[3] Hence an infected pregnant woman was four to five times more likely to be admitted to hospital than a non-pregnant woman (RR 4.3, 95% CI 2.3?7.8). Women in all three trimesters of pregnancy were in the series. The commonest reported underlying condition for the 34 women was a history of asthma (seven women). However, only one woman was regularly taking medication for asthma and generally chronic underlying conditions were under-represented (if pregnancy itself is excluded) compared with other persons hospitalised or dying in association with influenza A(H1N1)v.[3] The signs and symptoms reported for the pregnant women were no different from those reported for infected non-pregnant women or all others infected, except that they more often included shortness of breath. Three case examples from the hospital series, including one death, were published earlier see Box, below.[1]
ECDC Comment (4 August 2009)
This analytic study found that pregnant women were at higher risk for influenza-associated complications compared with women who are not pregnant and this risk may be even higher for pregnant women with underlying medical conditions such as asthma. This has been previously observed with seasonal influenza and during the 1918 and 1957 pandemics.[4?7]
Previous studies of seasonal influenza and pregnancy have found that the risk of severe disease increased as pregnancy progressed from the first to the third trimester.[4,5] No difference in experience could be detected for the trimester of pregnancy in this study but the numbers were really too small at this stage to detect such differences. One of the studies found the presence of underlying medical conditions increases the risk of hospitalisation but that has not been the obvious experience with A(H1N1)v influenza.[3,4] This increased risk of complications is thought to be related to several physiological changes that occur during pregnancy, including alterations in the cardiovascular, respiratory and immune systems.
The impact of the pandemic on the pregnancy itself, the unborn child and the newborn, remains to be described, though during the 1918 and 1957 pandemics there were reports of increased risk of miscarriage, premature delivery and other adverse outcomes.[6?8]
These findings indicate that pregnant women deserve particular care during a pandemic and some countries have already issued guidance for maternity services and clinicians.[3,9,10,11] The consistent finding of primary viral pneumonia and its association with a poor outcome is disturbing.
Although little is known about the safety or effectiveness of the use of antivirals during pregnancy, any potential risk for the foetus or pregnant woman is likely to be outweighed by the expected benefits of its use in a pandemic. Consequently, the antivirals that are effective against A(H1N1)v virus, oseltamivir and zanamivir, have recently been licensed for such use by the European Medicines Agency (EMEA).).[12] The UK and the CDC interim guidance for clinicians recommend that pregnant women with confirmed, probable or suspected infection with influenza A(H1N1)v virus should receive antiviral treatment. The drug regimen should be initiated, if possible, within 48 hours of the onset of symptoms. In addition, the American guidance suggests that pregnant women in close contact with a person with confirmed, probable or suspected infection with influenza A(H1N1)v virus should receive a 10-day course of chemoprophylaxis with oseltamivir or zanamivir. By contrast, the authors of the UK guidance do not feel this is necessary.[10,11]
The American guidance suggests that in clinical settings, including settings that provide care for pregnant women, patients should be screened for signs and symptoms of febrile respiratory illness at the initial point of contact, and promptly segregated and assessed. Because of the increased risk for severe complications, the public health response to outbreaks of influenza A(H1N1)v infection should include considerations specific to pregnant women.[3,9?11]
Box: Case examples[1]
Patient A. A 33-year old woman at 35 weeks? gestation had a one-day history of myalgia, dry cough and low-grade fever. Four days later her symptoms worsened and severe respiratory distress developed. That same day she was put on mechanical ventilation and a caesarean delivery was performed. The baby was healthy and was discharged home but the mother developed acute respiratory distress syndrome (ARDS) and died, despite receiving oseltamivir and antibiotics. A specimen from the woman was confirmed positive for influenza A(H1N1)v.
Patient B. A 35-year old woman at 32 weeks? gestation had a one-day history of shortness of breath, fever, cough, diarrhoea, headache, myalgia, sore throat and inspiratory chest pain. A rapid influenza test was negative and she received a parenteral nonsteroidal anti-inflammatory medication, acetaminophen, and inhaled albuterol and was discharged home. The next day she was seen by her obstetrician and a specimen was taken and infection with influenza A(H1N1)v virus was confirmed. After receiving additional treatment (not including oseltamivir) she recovered fully and her pregnancy proceeded normally.
Patient C. A 29-year old woman at 23 weeks? gestation had a one-day history of cough, sore throat, chills, subjective fever and weakness. One of her sons, aged 10 years, had similar symptoms a week before the mother and another son, aged seven years, had become ill on the same day as the mother. A specimen from the mother was confirmed positive for A(H1N1)v. After being prescribed oseltamivir her pregnancy proceeded normally.
- Centers for Disease Control and Prevention. Novel Influenza A(H1N1) Virus Infections in Three Pregnant Women ? United States, April?May 2009. CDC MMWR, Weekly May 15, 2009 / 58(18); 497-500.
- Centers for Disease Control and Prevention. Hospitalized Patients with Novel Influenza A (H1N1) Virus Infection ? California, April?May, 2009 MMWR May 22, 2009 / 58(19);536-541 http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5819a6.htm
- Jamieson D, Honein M, Rasmussen S, Williams J, Swerdlow D, Biggerstaff M, et al H1N1 2009 influenza virus infection during pregnancy in the USA. Lancet 2009; July 29, 2009 DOI:10.1016/S0140-6736(09)61304-0 http://www.thelancet.com/journals/la...304-0/abstract
- Dodds L, McNeil S, Fell D, et al. Impact of influenza exposure on rates of hospital admissions and physician visits because of respiratory illness among pregnant women. CMAJ 2007; 176: 463?68.
- Neuzil K, Reed G, Mitchel E, Simonsen L, Griffin M. Impact of influenza on acute cardiopulmonary hospitalizations in pregnant women. Am J Epidemiol1998; 148: 1094?102.
- Freeman D, Barno A. Deaths from Asian influenza associated with pregnancy. Am J Obstet Gynecol1959; 78: 1172?75.
- Harris J. Influenza occurring in pregnant women. JAMA1919; 72: 978?80.
- Coffey V, Jessop W. Maternal influenza and congenital deformities. A follow-up study. Lancet 1963; 281: 748?51.
- Department of Health (England). Pregnancy, Breastfeeding and Swine Flu A/H1N1. London, UK 2009 http://www.dh.gov.uk/en/Healthcare/Children/Maternity/ Maternalandinfantnutrition/DH_099965
- Centers for Disease Control and Prevention. Pregnant women and novel influenza A (H1N1) Virus: Considerations for Clinicians. June 30, 2009 10:19 AM ET http://www.cdc.gov/h1n1flu/clinician_pregnant.htm
- Royal College of Obstetricians and Gynaecologists, Royal College of Midwives and Department of Health (UK) Managing pregnant women with suspected swineflu London July 2009 http://www.rcog.org.uk/files/rcog-co...%20final_0.pdf
- European Medicines Agency CHMP assessment report on novel influenza (H1N1) outbreak Tamiflu (oseltamivir) and Relenza (zanamivir), May 2009 EMEA/CHMP/287662/2009 http://www.emea.europa.eu/humandocs/...28766209en.pdf
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