2009 Pandemic Influenza A (H1N1) in Pregnant Women Requiring Intensive Care --- New York City, 2009

2009 Pandemic Influenza A (H1N1) in Pregnant Women Requiring Intensive Care --- New York City, 2009
Weekly
March 26, 2010 / 59(11);321-326

Pregnant women are at increased risk for severe illness and complications from infection with seasonal influenza (1--3) and 2009 pandemic influenza A (H1N1) (4--6). To characterize the severity of 2009 H1N1 infection in pregnant women, the New York City Department of Health and Mental Hygiene (DOHMH) conducted active and passive surveillance for cases of 2009 H1N1 infection in pregnant women requiring intensive care. This report summarizes the results of that surveillance, which found that, during 2009, 16 pregnant women and one who was postpartum were admitted to New York City intensive-care units (ICUs). Two women died. Of the 17 women, 12 had no recognized risk factors for severe influenza complications other than pregnancy (7). All 17 women received antiviral treatment with oseltamivir; however, treatment was initiated ≤2 days after symptom onset in only one woman and was begun ≥5 days after symptom onset in four women. Because initiation of antiviral treatment ≤2 days after onset is associated with better outcomes (5,6), pregnant women should be encouraged to seek medical care immediately if they develop influenza-like symptoms, and health-care providers should initiate empiric antiviral therapy for these women as soon as possible, even if >2 days after symptom onset. Health departments and health-care providers should educate pregnant and postpartum women regarding the risks posed by influenza and highlight the effectiveness and safety of influenza vaccination. Obstetricians and other health-care providers should offer influenza vaccination to their pregnant patients.

To identify cases of 2009 H1N1 infection in pregnant and postpartum women, beginning April 25, 2009, DOHMH conducted surveillance for hospitalizations and deaths during three separate periods. Surveillance methods varied as the 2009 H1N1 pandemic evolved and influenza activity changed in New York City. During April--June, DOHMH conducted citywide active surveillance for deaths from 2009 H1N1 and enhanced citywide surveillance for hospitalized cases of influenza in pregnant and postpartum women, actively requesting specimens and testing for 2009 H1N1 at the New York City Public Health Laboratory. During July--September, influenza activity was low in New York City; however, ongoing passive surveillance was conducted for hospitalized patients who tested positive for influenza A. During October--December, citywide surveillance was passive, except active surveillance was reestablished at five sentinel hospitals. During all three periods, data on pregnancy, ICU status, and vital status were collected for all patients hospitalized with 2009 H1N1 throughout New York City. Chart abstractions for all identified cases were conducted by medical epidemiologists at DOHMH. For this case series, a case was defined as severe illness with laboratory-confirmed or probable 2009 H1N1 infection* in a woman who was pregnant or postpartum (within 6 weeks of delivery), resulting in admission to an ICU or death.

During 2009, a total of 17 patients (16 pregnant women and one who was postpartum) met the case definition; nine were admitted to ICUs during April--June, and eight were admitted during October--December. No patients met the case definition during July--September. Median age of the patients was 23 years (range: 20--37 years), and median gestational age at hospital admission was 34 weeks (range: 6--41 weeks) (Table). Median length of hospital stay was 12 days (range: 4--38 days). Five of the 17 women had risk factors for severe influenza complications recognized by the Advisory Committee for Immunization Practices (ACIP) other than pregnancy (7). One patient had asthma and cardiovascular disease (diagnosed postmortem). The other four patients had sickle cell disease, asthma, seizure disorder, and diabetes mellitus, respectively. Only one of the 17 patients had received 2009 H1N1 vaccine, according to the medical records; she had been administered H1N1 vaccine >4 weeks before hospitalization, after being administered seasonal influenza vaccine >8 weeks before hospitalization. Eleven of the 17 women were in their third trimester, including five who developed acute respiratory distress syndrome (ARDS). All 17 women received antiviral treatment with oseltamivir; however, treatment was initiated ≤2 days after symptom onset in only one woman and was begun ≥5 days after symptom onset in four women; initiation of antiviral treatment ≤2 days after onset is associated with better outcomes (5,6).

Four of the nine women who gave birth during their 2009 H1N1 hospitalization had an emergency cesarean delivery; eight infants were live-born (including one who died soon after birth), and one was stillborn. Six of the eight live-born infants were admitted to a neonatal ICU.

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