Researchers at the University of Texas Southwestern Medical Center in Dallas found nausea and vomiting -- usually signs of flu in children but not in adults -- were common in pregnant women with flu.
"Both physicians and patients should be aware of these findings so treatment is not delayed," study lead author Dr. Vanessa Rogers said in a statement. "I think our findings should encourage people to be vigilant and to take symptoms seriously."
Rogers and colleagues examined 107 pregnant women diagnosed with influenza at Parkland Memorial Hospital in Dallas during the 2003-2004 flu season. Ninety-three percent of the women had a cough and 89 percent had fever -- common signs of flu -- but 85 percent had a "profound" elevated heart rate and 60 percent had nausea and/or vomiting.
Nearly two-thirds were sick enough to require hospitalization. The most common complication -- pneumonia -- occurred in 12 percent of the cases.
The study, published in Obstetrics and Gynecology, found no significant difference in complications between women with flu and women without flu who gave birth at the hospital during flu season. After birth, the babies also showed no significant difference in complications.
"Early diagnosis and treatment might be the reason our patients did so well," Rogers said.
CDC: Get your flu vaccine