H1N1 Influenza in Pregnant Women Linked to Obstetrical Complications

Laurie Barclay, MD

May 24, 2010

May 24, 2010 — H1N1 influenza in pregnant women is linked to obstetrical complications, according to the results of a case series and observational analysis reported in the May 24 issue of the Archives of Internal Medicine.

"Pandemic novel influenza A(H1N1) is a substantial threat and cause of morbidity and mortality in the pregnant population," write Andrew C. Miller, MD, from the State University of New York Downstate Medical Center and Kings County Hospital Center in Brooklyn, New York, and colleagues. "Little data have been reported regarding the impact of H1N1 on pregnant patients or the gestational fetus, and published reports have been conflicting. However, during prior seasonal influenza epidemics and pandemics, pregnant women have been reported to have increased hospitalization rates, increased morbidity and mortality, but no increase in congenital birth defects."

At 2 academic medical centers, 18 pregnant women with H1N1 were identified based on direct antigen testing (DAT) of nasopharyngeal swabs, and the diagnosis was confirmed using real time reverse-transcriptase polymerase chain reaction analysis (rRT-PCR) or viral culture.

The investigators collected data on patient demographics, symptoms, hospital course, laboratory and radiographic results, pregnancy outcome, and placental pathology and compared these with published reports of the H1N1 outbreak and reports of the influenza pandemics of 1918 and 1957.

Mean age was 27 ± 6.6 years (range, 18 - 40 years); 2 women (11%) were healthcare workers, 15 (83%) were black, 2 (11%) were Hispanic, and 1 was white (6%). None reported recent travel. Asthma, sickle cell disease, and diabetes were the most common comorbid conditions. Gastrointestinal or abdominal symptoms were the presenting complaint in half of the women, and 13 women (72%) met criteria for sepsis.

On initial or repeated DAT, 14 patients (78%) tested positive for H1N1. Viral culture or rRT-PCR diagnosed H1N1 in the other 4 women (22%). Beginning on the day of admission, all 18 women received treatment with oseltamivir phosphate, and 3 (17%) were admitted to the intensive care unit. Median length of hospital stay was 4 days.

During hospitalization, 7 women (39%) delivered — 6 prematurely and 4 by emergency caesarean delivery. There were 2 fetal deaths (11%) but no recorded maternal mortality.

"Admitted pregnant patients with H1N1 are at risk for obstetrical complications including fetal distress, premature delivery, emergency cesarean delivery, and fetal death," the study authors write. "A high number of patients presented with gastrointestinal and abdominal complaints. Early antiviral treatment may improve maternal outcomes."

Limitations of this study include observational design, lack of controls, and small sample size. In addition, not all patients with influenza-like symptoms were tested, and confirmatory viral cultures or rRT-PCRs were not performed on all negative samples.

"H1N1 poses a serious health threat to pregnant patients," the study authors conclude. "Direct antigen testing is not sufficiently sensitive to diagnose influenza in pregnant patients presenting with an [influenza-like illness]. If a high index of suspicion exists, patients should be empirically treated with antiviral agents."

The study authors have disclosed no relevant financial relationships.

Arch Intern Med. 2010;170:868-873.

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