Influenza, also known as the flu, spreads in a seasonal pattern annually. Pregnant women are at high risk of influenza infection and are more likely to develop into severe illness and complications after infection. Influenza infection can also lead to adverse effects on the fetus and newborn. Studies in China suggest that pregnant women are generally susceptible to influenza. The risk of developing serious disease in pregnant women increased to 3.3 times (95%CI 2.7 to 4.0) compared with normal healthy women of childbearing age. Influenza infection in pregnant women is related to adverse pregnancy and delivery outcomes, mainly in hospitalized patients, particularly pregnant women with severe influenza. Numbers of foreign studies have confirmed that influenza vaccination during or before pregnancy can provide protective effect against flu, and vaccination during pregnancy can reduce the morbidity of influenza infection and mortality in pregnant women and their infants. Influenza vaccination also provides protection on maternal-fetal outcomes, reduces the risk associated with influenza infection such as placental abruption, preterm birth, low birth weight, small for gestational age infants and so on. Although a large number of international clinical trials, observational studies, data from post-marketing adverse events reporting system and related clinical guidelines have confirmed the safety of influenza vaccination in pregnant women, the coverage rate of influenza vaccine in this population remains low and the determinants mainly include cognitive attitudes towards influenza and the influenza vaccine, vaccination history, willingness to pay for the influenza vaccine and recommendations from healthcare professionals. The data of the safety evaluation of influenza vaccination for pregnant women is insufficient in China. Some influenza vaccine package instructions still list pregnancy as contraindications. This study reviews the epidemiological characteristics of influenza in pregnant women and epidemiological studies on influenza vaccines to provide scientific evidence for the formulation of relevant prevention and control policies and related research.

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