Upper respiratory tract infections include the common cold and sinus infections, which can lead to lower respiratory problems, such as asthma or pneumonia.
Senior author Martha M. Werler of the Slone Epidemiology Center at Boston University says eating nutritious foods, especially fruits and vegetables, improves immunity but that hadn't previously been associated with reducing the risk of upper respiratory infections in pregnant women.
The study of more than 1,000 pregnant women, published in the journal Public Health Nutrition, found those who ate the most fruits and vegetables were 26 percent less likely to have a upper respiratory infection relative to those who ate the least amount.
It has been recommended that pregnant women consume at least five servings of fruits and vegetables per day.
"Pregnant women may require more fruits and vegetables than usual because of the extra demands on the body," Werler said in a statement.