Master Class

Ob.Gyns. on the Front Line in the H1N1 Flu Pandemic


Each of the six women who succumbed developed acute viral pneumonia and subsequent acute respiratory distress syndrome requiring mechanical ventilation. (There were 45 total deaths reported during this period.)

Overall, just as it was in the 1918 pandemic, the highest mortality in the current pandemic appears to be occurring in the healthiest segments of the population—those in their late teens to late 40s—rather than in the very young and elderly (in addition to the chronically ill) as is typical for seasonal influenza. There is some evidence that suggests this increased mortality among the young, healthy population is due to a phenomenon called “cytokine storm,” or cytokine dysregulation. The body launches such a robust, overly exuberant immune response that it becomes self-destructive.

How this relates to pregnant women is unclear, as is their overall higher risk for more severe disease, complications, and death. There is speculation that their higher morbidity and mortality risk with influenza relates to immunologic changes in pregnancy, alterations in their respiratory physiology, and/or the overall greater metabolic demands of pregnancy. At this point, however, the testing of these hypotheses with the necessary animal studies has not been done.

In Practice Today

Therapeutic recommendations are driven by this history of pandemic influenza and the outcomes for pregnant women, as well as experience thus far with the current H1N1 influenza pandemic. Because pregnant women tend to have such a rapid onset and progression of disease, it is important to treat women at the time they present with symptoms, rather than waiting until these patients get worse or until culture results have been obtained.

The CDC has recommended that symptomatic pregnant women be treated with oseltamivir (Tamiflu), an antiviral neuraminidase inhibitor, as soon as possible after the onset of symptoms, and that pregnant women with significant exposure receive a prophylactic course of oseltamivir or zanamivir (Relenza). The benefit is expected to be greatest when treatment is initiated within 48 hours.

(In the CDC's Lancet-published report on H1N1 in pregnancy, the earliest initiation of oseltamivir in the pregnant women who died was 6 days after symptom onset.)

The vast majority of patients who have influenza—at least 80%—will present with a fever. Cough, sore throat, and muscle aches are other common symptoms. Occasionally, patients will have nausea or vomiting. During an active influenza pandemic, if a pregnant patient presents with signs and symptoms consistent with an influenzalike illness, we should err on the side of caution and begin empiric treatment.

In cases in which the diagnosis is unclear—in a patient with new nausea and vomiting but no fever or other symptoms suggestive of influenza, for instance—it is critical that we caution patients to call right away if they develop respiratory symptoms and/or a fever.

Because of concerns regarding the potential side effects of the antiviral medications, pregnant women can be expected to be hesitant about initiating treatment. However, given the increased risks of significant morbidity and mortality associated with untreated influenza infection, the risk-benefit ratio strongly favors the early initiation of effective antiviral medication.

Pregnant women are in the CDC's high-risk category for early vaccination, and certainly this is the best way to prevent their risk of significant morbidity and mortality. It is important that we educate our support staff to encourage patients to receive the vaccine; studies have shown that flu vaccination rates were low when nurses and front office staff were not committed to and invested in the idea.

There is only a small chance that individuals will acquire the seasonal influenza strain, but because pregnant women face increased risks with seasonal influenza as well, the CDC has recommended that they should still receive the seasonal influenza vaccine.

Vaccination also will protect pregnant women against the potential dangers of sequential influenza infections; being compromised with an infection of seasonal flu would potentially further increase a pregnant woman's risk of becoming severely ill with a subsequent pandemic H1N1 infection.

Public health measures call for “social distancing” as a nonpharmacologic method of influenza prevention—that is, these measures recommend limiting the number of people one is surrounded by or exposed to. Such measures have special meaning for us as obstetricians. It is imperative that we see infected and noninfected patients at separate time periods and/or in separate locations, and that we limit the numbers of pregnant women coming into our offices for prenatal care in the midst of a pandemic.

The use of masks and other standard infection control procedures also is imperative, and will help decrease viral transmission. But we must do more. We don't want one infected patient sitting in our waiting room with 10 other noninfected patients. Given what we know about the transmissibility of the virus, at least three or four of them would become infected in such a scenario.


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